Some puzzles concerning flash photograhy using electronic and mechanical shutters

Well as usual, my puzzler is puzzled about quite a few things. One of them is do with photography and the way in which the mechanical shutter curtains coordinate with a flash and how the same thing is achieved with an electronic shutter. You see, my Olympus OMD EM-1 Mark II has both electronic and mechanical shutters.

Most mechanical shutters consist of a front and a rear curtain. We don’t often think about how they operate but if you want to see, there is a high-speed video at this link (https://www.youtube.com/watch?v=ptfSW4eW25g). The link shows the shutter operation for a DSLR , a camera with a mirror but the two curtain system is much the same as that found in a mirror-less camera. In a mirror-less camera, the imaging chip is normally on and open to the light entering through the lens. The image the chip is producing is displayed on the LCD display and/or in the electronic view-finder (EVF). When you press the shutter button the front curtain of the shutter falls and stops light from entering, after this the sensor chip is switched off, and any information that may have been present in the pixels is erased. The sensor chip is then turned back on and the camera opens the front curtain, light pours in forming an image and the exposure is terminated by the rear curtain of the shutter that rises to block off the light. For relatively long exposures, less than say 1/250th of a second, the two shutters move independently; the front curtain is fully open before the rear curtain terminates the exposure. For shorter exposure times the shutters move together, the front shutter moving up with the rear one creating a slit, the width of which determines just how long any row of pixels is exposed to the incoming light. The “shutter rate” is defined by the speed at which the shutter curtains can move and the “exposure time” by how long any row of pixels sees the light. A third factor is “shutter lag” which can be thought of as the ‘thinking time’ of the camera – when you press the shutter button, actually nothing in the way of image formation occurs, rather the camera’s electronics get themselves ready to take a picture, the front curtain falls, and the imaging chip is erased. Shutter lag is important because if you trigger a camera using a laser trigger or other device in order to image a fast-moving object, the trigger pulse is sent to the camera in a few microseconds or less, but the camera doesn’t get round to recording an image for the period of the shutter lag which can be many milliseconds (a typical value for a DSLR is about 50ms). Mostly shutter lag is short enough that it doesn’t matter much. However, it does if you want to catch an image of a speeding bullet. This is because you can trigger the camera as quickly as you like but by the time processes described above have occurred, the bullet has long gone. The solution to that problem is to work in the dark with the shutter open and then form the image with a very brief flash of light. It should be clear that there is a big difference between the ‘shutter rate’ (the speed at which the shutter curtains rise and fall – relatively slow processes) and the ‘exposure time’ (how long a row pixels is exposed to the light). Some point and shoot cameras have such long shutter lag times that even slow moving objects have beetled-off between pressing the shutter-release button and the camera getting round to taking the picture – very annoying!

When you want to take a flash photograph it is important that the whole of the sensor chip is exposed to the light at the same time and thus that neither of the shutter curtains is blocking the light. It is for that reason that the flash ‘sync speed’ (exposure time) is limited to 1/250th of a second or less because for shorter exposures the two shutter curtains have to travel together forming a slit which would lead to only a band of pixels on the sensor chip being exposed to light during the brief flash from the strobe.

There are just a couple of other things to mention about flash photography and shutter curtains. Most cameras allow you to either fire the flash when the front curtain first opens i.e. at the beginning of the exposure or at its end when the rear curtain is about to rise. What difference does that make? Well if you take, a say 1 second exposure in dim light and have the flash go off at the beginning (front curtain sync), an object moving from left-to-right in the frame will be shown frozen on the left of the frame due to the light from the flash and then, by virtue of the ambient light, as a blur to the right as it continues to move across the frame. The opposite will be true if the flash is fired at the end of the exposure (rear curtain sync). Whether you want one or the other depends on how you want the image to look.

Try as I might, I was unable to find out exactly how a flash gun can be synced to an electronic shutter. Nearly all cheap point and shoot cameras have flashes that sync perfectly with their electronic shuttering. Though unknown to many of its owners, the Olympus OMD-EM-1 Mk 2 camera that I own, can also sync a flash to its electronic shutter. That this is little know is probably because that option is buried deep within that camera’s somewhat complex menu system.

I decided I needed to to understand how electronic shuttering works. Normally, a mirror-less camera is in ‘live view’ mode with the images it captures being sent to the LCD and/or EVF. When the shutter button is pressed, the imaging chip is erased and then for a period commensurate with the exposure time, allowed to accumulate information about the light intensity which is then read out and stored. That processed rolls down the sensor chip so once again there is a difference between “shutter rate” – the rate at which the process described above rolls down the sensor chip, and the exposure time – the length of time the pixels on the chip accumulate light.

The well-known “rolling shutter effect” is a direct result of the relatively slow shutter rates of both electronic and mechanical shutters….but which of them has the faster shutter rate? Here are some pictures I have taken to try to demonstrate the rolling shutter effect. Note they also illustrate the difference between exposure time and shutter rate – exposure time here is 1/8000th of a second but the shutter rate is much slower (for various reasons, I think it takes about 1/320th of a second for the pair of shutters to move across the sensor in my camera). It’s pretty clear from the photos that the distortion caused by the shutter rate is much worse for the electronic shutter which I think implies that it takes a lot longer to complete a readout of the whole sensor than it does for the mechanical shutter curtains to travel across the sensor chip. Interestingly, and for reasons I don’t quite understand, the image from the electronic shutter is crisper. I guess the more marked rolling shutter effect when using the electronic shutter is unsurprising because if my suppositions are correct, then for the mechanical shutter all the pixel rows were cleared before the shutter curtains started to travel and are read-out after they have closed. Thus, the distortion is solely the result of the time it takes the slit between the shutter curtains to expose the sensor. Whereas, for the electronic shutter even though the exposure times that it is capable of are far shorter than for the mechanical shutter, the shutter rate is quite a lot slower because row after row of pixels have to be cleared, set to on and read out during the exposure.

The image at the top shows the circular saw stationary. The centre is a shot at 1/8000th using the mechanical shutter of the OMD EM-1 Mk2. The image at the bottom is the result using the same exposure time and the electronic shutter. The difference in the rolling shutter effect is quite extraordinary!

So while electronic shutters can manage much shorter exposure times than their mechanical equivalents they have the disadvantage due to their slower shutter rate, of distorting moving objects. The big advantages of the electronic shutter are that nothing moves – it is err umm entirely ‘electronic’ so its operation is silent, there is no mechanical judder and thus no camera wobble to blur the image, and there is no wear and tear as there would be were it mechanical. A further big disadvantage of electronic shutters is the relatively slow flash sync speed.

As mentioned above, it seems a relatively poorly known fact that you can use a xenon flash with the electronic shutter of the Olympus OMD EM-1 Mk2 camera. At first sight this may appear a bit of a paradox because most of the descriptions you find on-line of the operation of an electronic shutter imply the sensor is being cleared, exposed, and read out a line at a time. If only a single line were available to the light at any one time then a brief flash would only be caught by a few rows of pixels. I was puzzled and could not find an answer on-line as to exactly how an electronic shutter operates during brief exposures so, I set out to try to determine the answer by experiment. Since, my camera can at its maximum sync speed, sync a flash regardless of the power setting and thus the brevity of the light output, I reasoned that all the rows of pixels must be available to receive information when the flash fires. The exposure time in the picture below is 1/50th of a second (the maximum sync speed) and the flash duration is about 1/8000th of a second but the frame is evenly illuminated as it is even when the flash duration is reduced to 1/25000ths by turning the flash power down to a minimum. So, I believe that all the camera’s pixels must be cleared and then rapidly set to ‘on’ line-by-line just as they would be behind the mechanical shutter prior to the exposure. After that, they are allowed to accumulate light for 1/50th of a second before being read out very quickly also line-by-line. So, my tentative conclusion is that the sync speed limit of 1/50th second results from the time it takes to set all the sensor’s pixels to ‘on’, and read them all out. If you try to take a picture with a shorter exposure, only some of the rows of pixels are available to to form an image.

OLYMPUS DIGITAL CAMERA

A flash photo taken using the electronic shutter of the EM-1 Mk2 – maximum flash sync speed is 1/50th of a second.

OLYMPUS DIGITAL CAMERA

With higher shutter speeds using electronic shutter with a flash results in an image only being formed in the lower half of the frame

But how does an electronic shutter operate when set to faster exposure times? I decided to try to discover the answer by using a camera trigger to fire my camera and then after a delay to allow for the shutter lag, to then trigger a flash set to a very low power so that the flash duration is extremely brief. In this setup, the pixels that are available to receive light should be obvious in the images formed. What the images show is that there is a band of pixels available to receive the light that travels across the surface of the chip during the exposure and that the width of the band is directly proportional to the shutter speed. Presumably, at the leading edge of the stripe, rows of pixels are being made available to receive light and at the lower edge, those pixels are being turned off and the image information read out. The images are similar to those you would expect from a mechanical shutter but I haven’t made a mistake, this is the Olympus’ electronic shutter! Given what appears to be a mode of operation not disimilar to that of the moving slit found in a mechanical shutter,  could the exagerated rolling shutter effect associated with the electronic versus the mechanical shutter simply be down to the slower shutter rate? The maximum number of frames that the EM-1 can manage in high speed silent mode is about 60 per second (~17 ms per frame) suggesting a maximum scan rate of at least that. The 50 ms for the minimum exposure time to sync a flash in electronic shutter mode suggests a frame rate quite a lot lower than that when in normal silent shutter mode. However, both rates are significantly slower than that achieved by the mechanical shutter –  a frame in less than 4 ms (again note exposure time and shutter rate are different things). So, perhaps it is indeed all down to shutter rate.

The two exposures at the top are both 1/160th of a second, the one on the left is with the flash set to 1/128th power and the one on the right with it set to 1/32nd power – this is to show that the height of the band has nothing to do with the duration of the illumination. The flash at 1/128th power lasts about half the time of the less intense flash. The second row (left) is an exposure at 1/200th and (right) 1/250th. The third row (left) is at 1/320th and (right) 1/400th. The number of rows of active pixels is proportional to the exposure time.

If you know better what is going on PLEASE let me know because it is puzzling my puzzler – lots!

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More on ‘macro technique’

I am not a photographer. I just take photographs. I greatly admire photographers who capture moments that no one else can and I wish I could do the same. However, I very much enjoy ‘the world of small things’ that my cameras and lenses allow me to explore. While, I have little talent as a true photographer, I take some solace from having taught myself how to take tolerably good macro photos. In this post, the first of several on macro technique, I have dared to share a little of what I think I may have learnt.

When I first started in the world of ‘macro’, I found the techniques described on the web and in some books extremely confusing. Indeed, one author often flatly contradicted another. Below, I use those contradictions to explore the techniques that I now employ. However, there is a big question that everyone considering macro photography needs to answer before they begin: why do you want to take macro photographs? I use macro photography for several purposes. Firstly, to collect images of insects and plants so that I can later sit down to identify them in a field guide. Secondly, I take pictures to allow me to see features of the things that I find so beautiful that I cannot see with my naked eye. Finally, I do it because it opens my eyes and reveals a hidden world that we spend most of our time ignoring – and I love it. My techniques are far from perfect, and some of my preferences like traveling with minimal gear, are designed to collect images for reasons other than getting to optical perfection heaven! Others use techniques totally different to mine and they may take better shots than I do. Below are the things that work for me.

Contradiction no 1. You need a sophisticated camera – any camera, even your phone will do.

Well, this wasn’t really a question for me, I just love optical technology and have worked with the best of it all my life so, I have always had an SLR or more recently a fancy mirror-less camera. It is true that you can take excellent macro shots with any camera and indeed, your phone. However, you will have much better chances of success and generate much more detailed pictures with a good interchangeable lens camera equipped with a macro lens. You can get excellent results with a standard lens and extension tubes or with an accessory lens, but you really cannot beat a macro lens for sharpness. I have three: an Olympus ED f2.8 60mm (for micro 4/3rds), an AF-S VR Micro-Nikkor 105mm f2.8G IF-ED (for Nikon SLRs), and a Loawa (Venus) 25mm f/2.8 2.5-5x. The latter is a specialist lens for extreme macro and the first two are fantastically sharp macro lenses for two different camera systems. Macro lenses also make excellent portrait lenses. For me, a key characteristic of a good macro camera is not how sophisticated its ‘bells and whistles’ are, but rather how it ‘handles’. Two aspects of handling are key: the system has to be light and it has to be easy to maneuver. It is true that you could take brilliant macro shots of plants or dead insects with a massive plate camera. However, an hour or two on a hot day hiking over rough ground kneeling, squatting and lying down, over-and-over again. and trying to maneuver your camera into position between grass stems, and you soon come to appreciate ‘small and light’. I love my Nikon and 105mm macro lens but that rig weighs nearly twice as much as my Olympus OM-D EM1 Mk2 with its comparatively tiny 60mm macro lens and thus I nearly always use the latter. The Loawa lens is a very specialized lens; a kind of zoom microscope, for use only on a stand of some kind – more of that in another post. I would add that I also find my Olympus 40-150mm f/2.8 Pro zoom useful because though it is not strictly a ‘macro’ lens (ie it doesn’t go to a 1:1 reproduction ratio) it is good for ~1:5, is unbelievably sharp for a zoom, and is great for larger objects.

Contradiction no 2. You need a tripod – you can take good shots handheld.

If it’s flighty insects you are interested in then I find a tripod next to useless and even a monopod is way to clumsy and hard to maneuver. There are occasions where a tripod can be useful, for example when ‘focus-stacking’ or taking HDR photos but mostly by the time you have it set up, the thing you are trying to have photographed will have long gone! A tripod can be of use when photographing plants or insects that remain motionless but even then, a camera with a good image stabilization system can make it a lot easier to clamber over a barbed wire fence! If you want the perfect shot of say an orchid, you can protect it from the wind with a ‘light tent’ and light it with the sun plus accessory flashes – you will get brilliant studio quality shots. If that’s what you want, then that is what you should do though 90% of the time you will do nearly as well with a handheld camera and daylight. On the whole, I believe in traveling with your camera and taking as little kit as possible. I will not mention it elsewhere but something that seriously transformed my experience of macro photography was to ditch the neck-strap that came with my camera. I swapped it for a ‘Peak Slide Lite’ strap. This allows for the camera to hang by my side, around my neck if I want (I don’t!), and for me to slide it rapidly into place in front of my eyes. Quick adjusters allow me to change instantly the height at which the camera hangs. Straps like the ones from Peak seem so expensive (£55!) – grin and bear it – they make a big difference.

At some point you will want a tripod. Get one that is light but as solid as possible, and that has a ‘beam arm’ that can be swung out at right angles to the tripod. It needs to be possible to set it really low to the ground as well as to use it more conventionally. Tripods are a very personal choice. Try to borrow some or watch other photographers wrestling with their octopuses! Mine seldom leaves home but I do use it. Monopods? Yes, maybe. I find I can use a hiking stick as a support – you hold the camera against the stick and slide the camera down to where you want it. You can buy monopods that are also hiking sticks. Bean-bags – why not? But I never use them.

In summary, if I had to say what was key to a stable camera in most of the situations in which I take macro shots, it’s a good image stabilization system and good camera holding technique (see below). The 5 axes IBIS system in the Olympus is fantastic and being part of the camera body, it works with all lenses.

Contradiction no 3. You can only get really sharp picture with a flash – you don’t need one.

Both are true. I mostly take three kinds of pictures, all handheld – without a flash, with a flash used as a fill-in light source, with a flash where I try to eliminate all natural light. On a bright day in the South of France with the ASA set to 200 you can take ‘sharp enough’ pictures without any kind of lighting other than the sun. Indeed, most of the pictures I take are taken that way. Pictures taken by natural light look err umm, ‘natural’. Anything they lack in ultimate sharpness is often only visible to ‘pixel peepers’ and you have the delight of traveling light and being instantly ready for a shot. I say traveling light because a naked speed-light mounted directly on the top of the camera is not the way to take good macro shots. To look even vaguely natural, the light from a flash needs to be diffused. The little pull-out or clip-on diffusers for a flash are handy but not very effective at their job. You need something much bigger – a proper macro soft-box. There are lots of suggestions for home-built soft boxes on the web. You can make a really effective one with cardboard, duct tape, and tracing- or tissue paper. A soft-box will provide the all light you need but because the light comes from the diffuser rather than directly from the flash head, harsh shadows and specular highlights are reduced. The result is a softer more natural looking photograph. With a big soft box it matters less where the flash is mounted, and though off camera would probably be better than on, the rig becomes harder to handle, so mine stays firmly on the hot-shoe. Ring flashes, dual macro flash etc. all have their place but frankly a manual flash with a soft-box is a cheap and effective solution in most situations. Fill-in flash lets you operate at the optimal f number and exposure time (see below) as well as filling in the shadows. As a result, the photos taken can be sharper than when using natural light alone.

Well, overkill? I 3D printed this softbox for my Nikon where it looks a little less out of place. However, it works really well on my much smaller Olympus m4/3rds camera.

There are occasions when you may want to eliminate nearly all natural light and depend solely on the light from a flash-tube. What follows is only relevant to that situation. If you want ultimately sharp photos then there is nothing to beat a flash gun with the intensity turned down. The duration of the light flash from a speed-light is related to the intensity of the flash. Elsewhere on this blog, you will find an article where I measure the duration of a flash from a speed-light. At full power my Yongnuo 560 III speed-lights have a flash duration of about 1/300th of a second. That is really slow. Why? Because when you have a tiny object in front of your macro lens even a slow movement translates into a fast movement in terms of the number of pixels the object moves across on the camera sensor. So for example, if an object contains features such as the hairs on an insect body that have dimensions of say 10um then at a 1:1 magnification, a movement at 1mm/s translates into a movement of 33um during a full-power flash. The pixel pitch on my Olympus camera is about 3.3um so instead of occupying ~3 pixels on the sensor an object on the scale above now appears on 10 of them – it has been badly blurred. 1mm/s is only 3.6m/hour which is nothing compared to wind-speeds, the movements insects make or indeed, the trembling hands of the would-be macro photographer! This is not to say that you cannot get a decent photograph with a 1/300th exposure but if you turn the flash intensity down to say 1/32nd of full power, the flash lasts only 1/13000th of a second, a duration that will freeze almost all motion. While we have a way of freezing motion, this will not make up for a lack of focus – that is a separate matter (see below) .

The front of my giant macro softbox. The area of the diffuser is huge by comparison to that of the front of the Yongnuo 560 III flash gun.

Someone reading this might ask why did I start out by saying you may want to eliminate all natural light? When you take a flash photograph the sync speed is generally 1/250th of a second or slower. So, if there is a lot of natural light reaching the sensor, this will produce an image that is superimposed on that produced by flash, the image from the flash may be sharp but that formed by natural light may for the reasons I describe above, be in a different position on the sensor, or otherwise blurred. Ways round the problem of blur caused by having both natural light and some light from a flash is to either use a tripod, or minimize and put up with the blur, or eliminate as much of one light source as you can. The object of the kind of macro photography I am discussing here is to make the light from the flash as predominate as possible. Paradoxically, when that is the object, areas of shade then become the best places to take pictures. If you can’t work in the shade you can try to use your shadow to block out the light from the sun or choose an overcast day.

So how do you use a flash to overwhelm natural light? The key is to set up the camera so that natural light forms little or nothing in the way of an image. This can be done by selecting a low ASA – I usually use something between 64 and 200 ASA. Adding a neutral density filter (ND10 is good) will in most situations reduce the natural light entering the camera at 1/250th of a second to very low levels. The flash employed needs to be of sufficient luminous intensity (high guide number) to generate an image when operating at relatively low power levels say, 1/8th to 1/64th of maximum power. This will ensure that the flashes are of very short duration. For the flash to be bright enough, you need to be relatively close to subject say, less than 0.5m. The quality of the photo will be best when a large soft-box is employed. Pictures taken this way can look dramatic and perhaps unnatural but will if the focus is good, be critically sharp. By using a flash diffuser and shooting in RAW so that you can bring up the background in post-processing, it is possible to produce tolerably natural looking and sharp photos. It also provides in combination with a suitable trigger (see past blog posts), a way of taking pictures of insects in flight. The photographers out there that enjoy ‘high-speed photography’ to take pictures of projectiles, smashing pumpkins etc., will recognize the similarity between the techniques they employ and those described here. One thing worth adding here is that while motion-induced blur may detract from the technical excellence of a photo, it may well add to its artistic impact.

One of the first photos I took using the technique described here of overwhelming the ambeint light with that from a flash. I also used a laser trigger (see earlier posts). The technique is particulary good for stopping motion.

Entire books could be written about macro flash photography using several speed-lights and a ‘macro-studio’ but that is a subject for another post.

Contradiction 3 – You need to use a very small aperture to ensure you get things in focus – you need to use a large aperture to ensure things are sharp. (Focus!).

Really, we need to think here about the whole subject of ‘getting things in focus’. Nothing is more important in macro photography than ‘focus’ even if you are aiming for an artistic result, you need to know what will and will not be, in focus. The reason that focus is so important is that when you are close up to an object the depth of field (dof) becomes very small. My 60mm macro lens focused on an object 30cm away and set at f/8.0 has a dof of 4.6mm. Move into the closest it will focus (19cm) and open it up to its maximum f number (f/2.8) and the dof is 0.6mm! Pick up a short pencil and point it at a nearby edge and watch the point of it moving about – natural tremor makes focusing at high magnifications while hand-holding a camera very challenging. It doesn’t matter if you employ the techniques above to freeze motion, hand tremor and the sheer physical difficulty of setting the lens to a perfect focus mean that while you may have a photograph with some part of the object of interest in focus, it may not be the ‘right ‘part. Anyway, what is the right part? Let’s answer that question first. Obviously, it’s the bit you wanted to be in focus which for an insect will usually be the compound eye. Other things may be a little fuzzy but it’s the eye that draws the eye! In many cases, no matter how stopped down the lens may be the available dof will mean only certain features can be in focus in a single image (see below re: stacking). So, without using a tripod, how do you ensure a good focus? You could stop the lens down to say f/22. For the closest focus of my 60mm macro lens this will increase the dof to 4.3mm but that will cause diffraction blur and worse still, unless the predominant light is from a flash, the increased exposure time necessary will mean camera shake may increase to unacceptable levels. What to do?

Different photographers have different way of holding a camera. My way is if I can, to choose kneeling, standing or lying down, over squatting. Stability of your body and arms is everything. I keep my arms tucked into my sides and hold my breath once I start to focus until after I have made the exposures. My right hand on the camera grip and my left on the focus barrel. My camera is always set to single AF plus manual with ‘back button focus’. ‘Back button focus’ means setting the camera so that a button on the back of the camera takes over from the shutter release button where focusing is concerned while the shutter button just err releases the shutter! Back button focus sound trivial but actually it is key to getting sharp photos – try it. I use a single small central focus point for the AF. Usually, particularly if I have set the focus limiter on the lens to a suitable range, but not always, the focus will lock. If it doesn’t I use the focus barrel to get into focus. It’s good to have a macro lens with a long ‘throw’ that is to say that a large movement of the focusing ring causes only a small change in the focal point. I find the whole process of focusing is much easier if you have a focus peaking setting on your camera. Focus peaking highlights in a colour of your choice, the pixels on the edges of objects that are in focus. It isn’t a ‘must have’ but it is extremely useful. I always have my camera set to use its electronic shutter so there is no noise or shutter shudder and minimal ‘shutter lag’ (the time it takes after pressing the release button for the camera to actually take the picture). My camera is set to manual exposure so generally, I will have already set the aperture and shutter speed as I want them using a nearby plant or bush to get things right. If the object is very difficult by which I mean the wind is blowing, or it is moving around, I may set the camera to rattle off quite frames a second. Sometimes I will also bracket the exposure in either speed or aperture. When taking either single or multiple frames, I use an almost imperceptible rocking of my body to achieve perfect focus before hitting the shutter button. Using your camera as a machine gun seems an attractive way to go until you have to sort through the pictures to find one, if any, that is sharp.

To go back to the contradiction of a large versus a small aperture, the truth is that these things are trade offs between the dof available at any particular aperture, the loss of resolution that results from diffraction when light passes through a narrow aperture and ‘artistic’ considerations such as the ‘bokeh’ (the blur of objects in the background).The optical testing of lenses using charts dominates magazine reviews but in fact the most important aspect of lenses is how they perform in the real world. I generally seek to use an aperture around the best for minimal diffraction and best optical performance (f/5.6 to f/8.0 for the Oly 60mm) but shift from this if ‘needs must’. I generally try to work with shutter speeds higher than 1/300th but sometimes again needs must. Similarly, I’ll work at low ASAs (200) to minimise noise but if trying to shoot a Humming Bird Hawkmoth, I’ll go to much higher ASAs to get say 1/8000th of a second exposures to freeze its motion. Bottom line, everything is a trade off but it is as well to understand the principles involved.

Contradiction 4. You can’t have everything in focus at once. (Stacking).

Well that isn’t altogether true. By using a focus slide or the ability of some cameras, to take a series of photographs at different planes of focus, it is possible to have much more in focus than would be possible in a single shot. You do not need a fancy camera to do focus stacking. It can be done with a simple mechanical device that allows the camera to be moved forward in steps in the same orientation, or by focusing the lens at different points in different exposures, or by using the ability of some camera to do the equivalent of these maneuvers using the focusing mechanisms internal to the camera’s lens. Focus stacking, no matter how it is done takes time and thus is not suitable for subjects that may move. The process generally requires the camera to be fixed on a tripod or other support. It is a powerful process and is capable of producing some great pictures. It requires post-processing software that can remove the out of focus information, align and combine the images taken. I may cover this in another post.

Photos taken using stacking can contain details over the depth within and image that could not possibly be encompassed within a single shot.
The detail that a macro lens can achieve with stacking is extraordinary.

Contradiction 5. You will get the best macro shots on a butterfly farm or with home-reared specimens – it’s better in the field. The same might be said of botanical specimens?

Both are true. You can be pretty sure that a day out at a butterfly farm will provide some fabulous opportunities for shots of exotic butterflies from far away countries – so why not? If you can get some butterfly pupae and have them emerge at home that too will provide some fantastic opportunities for macro shots that you would be very unlikely to be able to take in ‘the wild’. However, neither of those two options allow for the fun of ‘hunting’ with a camera. I am going to boast that I am quite a good hunter but…. I used to be hopeless. Now, I know my prey. I know when and where different butterflies, and other insects will appear, where they are likely to settle and be least disturbed by my presence. How to move to reduce the possibility that they will fly off. When to wait, and when to move. It’s good to have read about the habits of the things you seek to photograph and which habitats they prefer – see for example Thomas and Lewington’s wonderful book, “The Butterflies of Britain and Ireland’. You soon learn not to let your shadow fall over a butterfly – it will fly away, not to come between a butterfly and the sun, and to move slowly and wear subdued colours. When you look at a butterfly, you will see a dark spot in the centre of its eye. This is the ‘pseudopupil’ and it is the region of the eye that is directed towards the point from which the eye is being observed. When you can see the pseudopupil the butterfly can see you, the bigger it appears the better its ability to see you. Start by taking shots at a distance then move slowly towards an insect of interest taking more shots as you go. Always watch the histogram! Nothing will make a poorly exposed picture great though shooting in RAW will offer more post-processing opportunities to get things right.

Photos taken handheld and using natural light can be sharp too!
Ditto! Even indoors with the light from a window.
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A Mostly Printed Focus Rail: The Gigapixel Project – Part 3

Well, times are weird but its good to have something to take one’s mind off all the terrible events in the outside world and this project is one of those things. I am posting this short update because the ‘Gigapixel Project’ is now fully functional – some bugs remain but I hope to be able to iron those out during this period of ‘lock-down’.

So how have things changed since the last post I made about a month ago? Since then, I have completed the 3rd (Y) axis and have the whole machine up and running. I am leaving some bells and whistles until later. I have for example, for test purposes made the ‘Gigapixel’ menu somewhat simpler than it will be in the end. I have set the duration for the ‘settle’ and ‘exposure’ times to be short – just a few seconds. The reason for this is to speed up the time it takes to test changes to the software. I have also set the X and Y overlaps between the pictures in a ‘gigastack’ to be 50%. I rediscovered the old cookie of C++ rounding errors and I am putting up with them for now. Any programmers among those reading those this post will know the problem – you do float arithmetic but you need an integer answer rounded up so you need to add 0.5 to the float result…..or use the ‘Math.h’ library that I recently rediscovered (!) that provides among many other very useful math functions, a round up command (ceil(value)). Putting this bug right will be easy. There are some others but all of them are pretty straightforward to fix. I have been excited to actually get the first pictures out of the machine so they can wait for now.

The machine – note the Y axis is currently fixed to the RH side but can easily be moved to the front or the left hand side. It’s fixed using tee-nuts.

I have added a menu that calculates the best Z step for an object given the magnification, f number etc. It returns exactly the same result that the tables on this subject on the Zerene Systems pages give (https://zerenesystems.com/cms/stacker/docs/tables/macromicrodof) which is reassuring. The ‘jog menu’ now returns the position in um from where one started jogging. This is useful because one can use ‘jog’ to determine the area one wants to include in a ‘gigastack’ as well as the front and back of an object for a Z stack. The work flow for a gigastack goes something like this: 1) determine size of the field of view i.e. what you can see on the display screen of the camera 2) determine the size of the object you want to create a gigastack from in X, Y and Z planes – ‘jog’ can be used for this or in some circumstances you can just use a ruler or even just plain guesstimate things 3) from the ‘calculator’ get the best Z step for the object. After you have provided this information the programme will tell you how many X and Y fields it will take to cover the object with 50% overlap in each dimension, how many Z stacks it will make, and how many pictures there will be in each of these. Obviously, even if you are demanding just say 5 x X, moves and 5 x Y moves, with say 20 slices in each Z stack, then you are going to have a lot of photos – 500 to be precise. 10 x 10 x 50 = WOW! Also, you will need to process the individual Z stacks to boil them down to single ‘all-in-focus’ pictures. After this it is over to ICE (see previous post), or Affinity Photo for smaller panoramas, to stitch everything together. A 5X x 5Y image from my camera will result in a 0.5GPix result or 2GPix in hi-res mode.

As I said above, ‘it’s a lot of photos’ so, there is an issue to do with the capacity of the flash guns to provide all the flashes even if set to say 1/64th normal power. To answer this problem, I am in the process of 3D printing ‘faux’ batteries that will allow the flashes to be powered from an external power supply so they can meet the demand placed upon them and also allow them recharge more rapidly. A similar problem may exist for the camera. I am using the Em1 Mk 2’s electronic shutter to give an extended battery time and reduce wear. For now, I have been testing the setup without the flashes – instead, just using the LED illuminators built into the Meike 320 flash guns. This is highly sub-optimal in terms of the quality of the pictures but good for tests because it eliminates the time that the flashes would otherwise need to recharge.

After many false starts with rails running backwards and all kinds of other things that resulted from programming errors, I got my first fully automated gigapixel image (actually much less that a GPix but hey, I am testing things out!). The images are pretty poor because I am not using a flash, the rails are moving on with with short times to settle, and lots of other excuses…. My first successful image was 3X x 3Y by 3Z, so just 27 images in 9 stacks of 3. Despite the poor images, I have to say I was pretty pleased. It’s eerie watching the camera/object move in three dimensions as the images are acquired. I am pretty impressed with the precision of the rails even though they currently have 8mm leads (I will replace them with 1mm lead lead-screws when (if?) China opens for business again). The programme rewinds the rails to the original point at the lower right-hand corner when it is finished and seems to be spot on when it does this even when working at higher magnifications.

Unimpressive though it maybe, here is the first image from the setup – for me it’s a milestone so it may look better to me than anyone else! Indeed, I am sure it does. The Z stack depth, and the number of photos with in each stack, were insufficient to provide a crisp image at every point but hey, once again it’s a test. I will add some better photos as I generate them and also a video.

The 9 outputs from Z stacking – this a crumpled 20 Euro note – I used Affinity Photo’s ‘focus merge’ facility to create each of these images from the 3 planes of focus. I was playing with the overlap so it isn’t exactly 50%!
A tiny version of the output – I used the Affinity Photo ‘panorama facility’ to create this image.

1 April 2020: I have added a YouTube video to show how the software works. I will add a 2nd movie to show the setup creating a macro panorama.

https://www.youtube.com/watch?v=oqjQab9gZ7Y

Finally, given the terrible times the world is suffering – I hope everyone remains safe. “All men are brothers now” (and sisters) – lets not forget it.

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A Mostly Printed Focus Rail: The Gigapixel Project – Part 2

Well, a certain number of things have come together while some others haven’t. I am waiting for an 8mm lead-screw with a 2mm lead to replace the current Z axis. This was ordered from China a little while ago but I suspect that given the problems with the Corona virus, there maybe a long delay. When I get it, the current Z axis that is functioning on an 8mm lead, will become the Y axis. However, with two axes working it became possible to create the XZ table and test some aspects of both its function and that of the available software. This post reports on the progress so far. So, below is a picture of the XZ table before I properly installed it on two 60cm 2020 maker rails. The base of the X rail has holes for the installation of 4 ‘tee-nuts’ which allows the whole XZ assembly to slide forwards to give a wider range of distance from the camera’s sensor plane to the object being photographed. This seems a good idea because it will allow me to use both my Olympus 60mm macro and my Lowa 2.5x to 5x ultra-macro lenses thus covering object sizes from about 15 cm in size down to a couple of millimeters across. I have to say that 2020 rail is amazing stuff and I can see all kinds of possibilities for its use, 2040, 4040 etc, elsewhere in my photography projects. Also worth mentioning is the performance of the 3D printed parts. Printed in black PETG 15-20mm thick with 20% infill and 6 vertical shells, they are incredibly strong and there is no ‘give’ or sag.

The 3D printed components temporarily connected together to check the fit. In the end I changed my ideas about ho to employ the rails mounting them across the width of the table – see below.

I decided to make a compromise between having the Y axis over the edge of a table and having it installed on the same surface as the XZ table. I created a box about 20cm high by 60cm long. The maker rails are bolted to this using tee-nuts. For smaller objects the Y rail can be installed directly to the front of the box – for larger ones it can operate over the edge of a table. My objective being to enable a significant distance between the object being focused and the background thus putting it well out of focus. In addition to the XZ table, the 2020 rails carry the brackets for two compact Meike 320P flash units. The brackets allow for a lot of flexibility in the positioning of the flashes.

My Olympus OM-D EM1 Mk2 with the Lowa super-macro lens mounted on the XZ rails (note the 2020 rails these span the width of the X rail). Y movements being temporarily supplied by a 2 axes manual focus rail. This is mounted on a board that bolts to the front of the set-up. A lash-up but a functional one!

Although I have yet to make the diffusers for the flashes, it seemed like a good idea to try out some of the software. I have started out by making some small stitched macro images. By small I mean up to 40 x 21 MPix images i.e. getting on for a GPixel when combined. Because I wanted to test the software I might use for stitching, I did not Z stack for these tests. Had I done that, I would be dealing with image sets consisting of upwards of several hundred photos! I am a great admirer of Affinity Photo so I started out trying to stitch with it. It worked but it was very slow and ‘fell-over’ unless it had a huge amount space available to it on my SSD. I tried HugIn but it was just two clunky and seemed not be able to cope at all. Finally, I turned to Microsoft ICE. I pointed ICE at a series of 34 overlapping RAW images and to my amazement it completed the stitching within 180 seconds compared to 15 minutes when using Affinity. The results were to my mind excellent…….

This image is of course tiny by comparison to the original – such are the restrictions of WordPress! However, even though the flashes were of slightly variable intensity, the result is seamless.

A detail from the image above, again at very reduced resolution.

To make the image shown above, while the X rail motor handled the X movements, I had to make the Y movements required by hand. Obviously, the ultimate aim is to have motion in all three axes handled by software. I am happy with the X and Z performance of the mostly printed focus slides. Next steps are to create the 3rd rail, write some more of the software to handle their movement, and make the flash diffusers etc.

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A Mostly Printed Focus Rail – Part 1

A long time ago now, I created a stepping motor-powered focus rail. It worked quite well but the parts were created in 10mm aluminium on my Sieg milling machine. Obviously, making such a thing is out of the reach of most people whose main interest is macro photography. At the same time, I made a control box to power the rail and that had provision to drive up to 5 stepping motors (for X, Y, Z and A and B axes). The control system is based on an Arduino Mega and Brian Schmaltz’s Easy Driver boards. Since a Mega clone costs about £10 and the driver boards can be bought for about £2 each, the electronics are not going to break the bank. Indeed, the most expensive part is the box to house the electronics! At the time, I had the vague notion of creating a set-up that would make it much easier to position small specimens in three dimensions and perhaps enable them to be rotated for stereo or ‘product’ photography. As time went on, though I made much use of my original focus rail, I failed to return to the project and create the copies of it required to give motion on all 5 axes. One can of course buy focus rails but the cost of three or more would be prohibitive – at least it would for me. So, I decided to take another approach, namely, to create a ‘mostly printed focus rail’ – an MPFR if you like. It uses parts you can recover from old printers and/or rails and lead-screws intended for 3D printers. Since a number of photographers own 3D printers, I hope that it will be possible for a number of them to create their own MPFRs. I haven’t calculated the cost of the parts I have used to create the prototype MPFRs but it is somewhere in the region of £20 each. When the project is up on ‘Thingiverse’ it will be possible to get the parts printed by a third party – I doubt that they would be very expensive to have them printed for you. While my design is different in many respects, and in differs its intended function, the MPFR leans on the efforts of other of the denizens of the ‘Thingiverse’ and when I post the design they will of course be credited – there is nothing entirely new under the sun.

So far, I have created a few prototype MPFRs. I am still working on some of the details of the final design. When it is complete, I will post the project on Thingiverse enabling anyone else who wants to, to create the rail. Meantime, I have updated the software that was running my old focus rail. I have removed the annoying bugs and changed things so it runs a little more smoothly. I have put the programme on Github. Currently it is a ‘private’ project but I am happy to give people access to the code or to send it by email. The long term aim on the software front is to automate the acquisition of stacks from different areas of a macro specimen so that they can be stitched into a single ‘gigapixel photograph’. That aim is already achievable by using X & Y rails to position the camera manually. I would be most interested if anyone wants to help develop the code which I plan in the long-term to transfer to a system that uses a touchscreen interface, possibly a mobile phone. I am not a professional programmer but I can vouch for the fact that the current code works and generates very nice Z stacks. An example of a z_stack from one of the prototype MPFRs is shown below.

example_MPFR_Z_stack

Simple 50 picture Z-stack. The eye in the needle is about 0.3mm across.

The current MPFRs work very well and are capable of steps as small as 5 microns. I am looking at the possibility of using a finer lead-screw on the Z axis to enable ~1 micron steps.

Gigapixel machines are available commercially but I take some pleasure from the fact they cost thousands of pounds – indeed this one http://www.gigamacro.com/gigapixel-macro-imaging-system/ costs $48,000. I suspect the machine I am working on will cost about 1/200th of that!

pic_prototype

A prototype MPFR which apart from the motor, 8mm stainless rails, the lead-screw and nut consists of 3D printed components.

Above is a picture of one of the prototype MPFRs to which I will shortly add a video on YouTube showing it working with the new control box software. When I have refined the parts of the rail further I will add some pictures of them. Used in a gigapixel machine, X and Z rails are combined as shown below and are designed to carry the camera. They are very like those you would find on a small milling or engraving machine – indeed, they could also be used for that purpose. The combined ZX axes are designed to sit on a box or a table. The Y MPFR is set at 90 degrees to the ZX table and is screwed to the front edge of the box. The Y axis that will carry the specimen will have an L-shaped bracket mounted on it to bring the object in line with the optical axis of the camera. When all three rails are complete, the wisdom or folly of the design will become apparent!

Gigapix_all_3rails

The way in which I envisage configuring 3 MPFRs to create a ‘gigapixel machine’. The illustration also goes to prove that ‘Tinkercad’ is not a ‘toy’!

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An LED Skinner-type moth trap

Two or three years ago, I had the idea of producing ‘a better moth trap’ using LEDs. Since then, several hundred people have read that blog post and several readers have made their own traps. One reader has produced a commercial version of an LED moth light and written a scientific paper on its efficacy.

About a year ago, I started work on producing another LED lamp unit designed to either operate either singly or as an array. The idea behind the concept was that a unit of 4 x 3W LEDs; royal blue, emerald green, UV and ice white, could be combined on a single heat-sink that was structured in such a way that one unit (12W) could be used as a bar in front of white sheet, two (24W) could be used in a V-shaped formation on a Skinner-type trap, and that four (48W) could be combined into a square array that could replace a mercury vapour bulb on a Robinson-type trap. Last night, I tried out the Skinner array (24W max). I chose the night based upon the fact that it was the time of year that the Giant Peacock Moth makes its appearance. These spectacular moths are up to 20cm across and are Europe’s largest moth.

IMG_4334IMG_4335

I powered the LEDs from an old laptop ‘brick’ power supply that is well-capable of providing the high currents necessary. I chose to run the LEDs in series rather than in parallel. This has the disadvantage that the different colour LEDs drop different voltages and thus do not all run at the same power. However, it works well enough and the power supply was for free.  As this was the first outing for this particular trap, and I was unsure how the heat-sink would cope, I put two hefty diodes in series with the 15V supply to drop the voltage by about 1V. Running the lamp on the bench I had found that this resulted in running at about half power. However, the lamp is still astonishingly bright and the heat-sink does not even get warm. The diodes used to drop the voltage do warm up a bit, but being 10A diodes they are well able to cope with this, and they get warm rather than hot to the touch. Next time I run the trap, I will do so with only one diode in the supply line (about  14.5V).

It was a warm and cloudy evening. I had not expected much. However, the results were nothing short of astonishing. I had hoped to attract a Giant Peacock Moth. However, instead they came in numbers. At first they flew around and it was hard to tell how many there were. One, then two, then three, then four, then five entered the trap. Two males that had been fluttering in the eaves of the covered terrace, settled quietly on the beams. One settled on the outside of the trap. I began trying to photograph them. While I cannot be sure, there were at least 8 or 9 of these moths and with several in flight around me, possibly as many as 15 or 20. These were not of course the only visitors. There were several hawk moths including a beautiful Elephant Hawk and dozens of smaller moths together with many beetles. Since the object of the evening was the Giant Peacock Moth, I paid little attention to the many other species.

The bottom line to this report is that the V-shaped array works very well with a Skinner trap. I believe the overall philosophy is correct – an LED light source that is rich at the blue end of the spectrum, tuned to the peak absorption of moth (and beetle) photoreceptors. I would add that my entire trap cost about £25 (not including the cost of the power supply). ‘Brick’ power supplies from old laptops are practically free at boot fairs or can even be had from new on eBay at very low prices where the laptops they were designed to be supplied with are now considered defunct.

I am writing a little blog-post on the Peacock Moth – you will soon be able to find it at petermobbs.com.

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Macro flash bracket and other macro tools for OM-D users

This blog entry describes several things I have made/used that make flash and macro photography easier for me; a trigger grip/bracket I have made to support two Meike Mk320p flashes, how to use such a setup in conjunction with remote pre-focus shutter buttons and the Keyline art filter to take perfectly (well, hopefully!) focused macro shots. It is specifically aimed at Olympus OM-D users though some of the tricks may be useful more generally. First, a word in praise of the Meike flash unit: it’s small, it’s versatile and it has a reasonable guide number and, above all, it is pretty cheap! Second, a word of explanation for why I have built such a setup. The answer is moderately complex! I sometimes need to take macro shots using flash. I like the technique in which you hold a single flash with a large diffuser in one hand and the camera in the other, or you mount the flash and the diffuser on the top of the camera. However you can’t really beat two flashes with diffusers for good macro lighting, and it is for this reason that both Nikon and Olympus will sell you a twin flash setup for macro. The Nikon and Olympus flashes mount on the lens or optionally on little stands. I have such a setup for my Nikon cameras – the R1C1 unit with the SU800 flash commander. The Olympus unit is also meant to be very good but both are pricey £400 – £600 and I don’t find the Nikon setup easy to hand-hold – it’s heavy and a bit tricky to steer. Since I already had one Meike flash, an extra 55 Euros to add a 2nd gun seemed a much cheaper way to go. However, I needed some kind of frame on which to mount the two flash units. For this, I turned to a newly acquired skill: 3D printing. More of this bracket later.

The OM-D E-M1 Mark 2 is equipped with ‘focus peaking’, and I use it a lot. I far prefer it to the ‘magnify’ option. Peaking shows you when an object is in focus by highlighting pixels on the in focus objects with the colour of your choice. ‘Magnify’, as its name implies, ‘bigs up’ the part of the image of interest so you can better see if it is in focus. I prefer ‘peaking’ because I find it annoying to lose sight of the majority of the field of view for a small selected magnified region. With ‘peaking’ you can see everything *and* see what bits of the image are in focus. Normally, these functions are activated when you turn the focusing ring on the lens. However, they can be allocated to buttons and then you can activate them by pressing say the ‘Fn1’ button. If you press the button, on comes the peaking and with its help you can move the object into focus without having to turn the focus ring. You press the shutter button and with a bit of luck you have a perfectly focused shot. Next shot press the Fn1 button and away you go gain. I love the focus peaking function and I used it all the time. However, a while ago, I came upon this: http://trevinchow.com/blog/2012/10/28/how-to-get-focus-peaking-with-the-olympus-om-d-e-m5/ – a way of adding a kind of ‘focus peaking’ to the old E-M5 Mk1 – back then it didn’t have that function built in. So, I had to try it. Basically, on the E-M1 Mk2 you simply set the Art Filter to ‘Keyline’ (number 11 in the Art Filter menu). As part of its overall effect, the Keyline filter highlights in focus pixels as black.  If you want ‘focus peaking’ to be available all the time without pressing any buttons before taking the shot, Keyline may be the way to go. In use, I set the camera to record a small jpeg and a RAW image. It’s a bit annoying to throw away storage on recording a Keyline image but they can easily be thrown away later and I find that it is worth it. I find it much easier to view the Keyline image on the live view screen than a focus peaking image and you soon realize that the in focus Keyline image ‘snaps’ when you hit exact focus. I have tried to demonstrate this with the photo shown below (forgive me for the fact it is taken with an iPhone – the object here is to demonstrate the effect rather than take wonderful photos!). You can of course go on using ‘focus peaking’ with the bracket – assign it to the Fn1 button and you can reach it from the RHS grip with your thumb. It is somewhat annoying that it seems you have to press that button for every shot – do let me know if there is a trick that lets you have it ON all the time.

You can use this Keyline peaking technique at any time; with or without flash, manual focus, single AF etc. though , unfortunately it does not work with proCapture but then nor does peaking. However, I find it most useful for when you want to take photos at a preset distance. This makes sense when you are using macro flash – your flash guns are set for objects at a certain distance both with respect to their angle and their power. Note that in the picture above the camera is viewing a curved sheet of paper. It is pretty clear (black pixels) what is in focus and what is not even though, the difference in the distance from the lens only change by a mm or two.

OK, so now to the bracket. I have used U-shaped brackets before to mount a camera along with various bits of electronics, for laser rangefinders, cross-beam laser triggers etc. I decided to try 3D printing such a bracket for two Meike flashes. At some point, I will want to add a range-finder laser trigger to this setup, indeed, it is ready to go, but that is another story! Here is a screen shot from Slic3R of the STL file for the bracket.

You will see it has two handles by which to hold the setup. They are oval and I find them pretty comfortable. I separately printed two trigger switch boxes that mount on the handles – one functions to set the camera to pre-focus and the other to fire the shutter.

When pressed, they connect the second and third ring respectively of a 2.5mm jack plug to its barrel. This plug inserts into the remote socket on the right hand side of the E-M1 and allows the buttons to take over the functions of the camera’s own shutter button. It is worth noting that separating the ‘pre-focus’ and ‘shutter’ functions has both advantages and disadvantages. For me the big advantage when doing macro photography is that ‘single AF (sAF) + manual’ is useful because it can, given reasonable light, in combination with the focusing range limiter on the lens barrel of the Olympus 60mm lens, very quickly focus the lens on the object of interest. This is fine if you immediately go from pre-focus to taking the shot without taking your finger off the shutter button. However, sometimes it would be more useful for macro shooting if you could use sAF to do the initial focusing and then remove your finger from the shutter button and use the technique of slightly rocking back and forth while taking photos. If you do this with sAF enabled every press of the shutter button will cause the camera to seek a new focus lock. Not so if you divorce pre-focus from the shutter button – use pre-focus button to get near to the focus you want and then use the shutter button as many times as you like without the camera seeking a new focus lock. The downside is that, for reasons that I do not understand, you have to press the pre-focus button briefly if you want to ‘chimp’ (view) your pictures. The picture of the complete setup shows how the pre-focus and shutter buttons are mounted and other images (above)  show Slic3R screen captures of the STL files for them.

The only other components of the system are the two little stands for the flash guns made from pieces cut from 50 x 25 rectangular 3mm aluminium tube drilled with holes on their bases tapped for 1/4 inch UNC tripod bolts. A 7mm hole on the side of these stands allows 1/4 inch UNC bolts to pass through to hold flash gun clamps (see the pictures). The stands provide a wide range of possibilities for positioning the flash units. Remarkably, this whole thing feels really good in the hand; secure precise and easy to maneuver. The downside is that you need to set the camera up by either holding the whole thing in one hand or by sitting down with it and doing that….but, it was the same with my Nikon R1C1 set up only that was MUCH heavier!

So, how well does it work? To test it, I set up the camera in full manual modem, set the aperture,  placed a 20 Euro note flat on my desk and then gave myself the minimum time to find the preset focus point and hit the shutter button.  I found that using the Keyline filter, I could have perfect focus in much less than a second. I repeated this about 20 times and each time I got nicely focused shots. As described above, one can also use Single AF to get the initial focus and then after letting go of the pre-focus button move the setup a bit to hit precise focus and then press the shutter button without pre-focus. It won’t be everyone’s cup of tea but it works for me!

I printed the bracket in PLA but I will be making the final version in ABS (or possibly  PETG). PLA seems fine but it isn’t good in the heat.

If you find anything here interesting or controversial (!), leave a comment and I’ll get back to you. If there is a demand, I will put the STL files on Thingiverse.

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