First, here is the subject. It's a moth pupa with a well developed adult forming inside. You can easily see the antenna inside its case, a couple of legs inside theirs, patterns forming on the scaled wings, and so on. This is a stereo pair, crossed-eye.
Here's a closer crop, showing more detail around that claw in the middle of the image. (The claw is located at the joint between tibia and tarsus, several segments above the foot. As far as I know, nobody is quite sure what the claw is good for. There are suspicions that it's used to help the critter drag itself out of the pupal shell and surrounding debris, to get somewhere that it can expand its wings.)
Direct lllumination for all these shots was provided by a single undiffused Jansjo lamp, cross-polarized. I had to kill surface reflections in order to get a good view of the subsurface detail. The subject is lying on a gray card which provides non-polarized back light. You can see how bad the surface reflections are, on the sides of the pupa. So that's interesting aspect #1, having to use cross-polarization just to see what I cared about.
Interesting aspect #2 is that I had to shoot the focus stack by hand, turning the fine focus knob of my focus block system. I tried to shoot it automatically, with stepper motor control. But this is a live specimen, and apparently there's something about the noise of a stepper motor that agitates the critter, because every couple of frames that leg with the claw would jump to a new location. I was worried that the camera's shutter action might be causing the problem, but fortunately it was not. Still, I'm thinking that a setup providing dead quiet operation and much faster acquisition would have been more robust.
Interesting aspect #3 is that this subject is extraordinarily subject to color shift due to metamerism. The camera sees light that comes from the inside of the pupa as much more red than it appears to my human eye. To produce a rendition that is anything close to what I saw by eye, I had to desaturate the colors across the board by a Photoshop Hue/Saturation layer with Saturation of -43. Here's a comparison of the images as adjusted and as shot, with the ridiculous red cast to the pupa even though the background is neutral gray as it should be.
Interesting aspect #4 may be seen in the second image, the stereo crop. If your stereo perception is good enough, you'll notice that the band of bright reflections just below the eye appears to be depressed below the rest of the surface. It looks almost like the pupa is dented in that area. But in fact the pupa is not dented, it's just that the reflections behave quite oddly in that area. Because the light source is very small, and the pupa is very shiny, and the lens aperture is pretty wide (NA 0.14), those reflections are highly vulnerable to the "utilized aperture" effect. Reflections from one side of the band use one part of the lens, while reflections from the other side of the band use another part of the lens, so as the lens is moved to focus, the reflections appear to move around in interesting ways that cause the stereo rendering to look dented. Here's a simple animation of the source frames. (Note: these reflections would be extremely bright and blown out if it were not for the cross-polarization. What you're seeing here is just the remnant light that got through the crossed polarizers. In the original images that remnant is quite a bit more blue, again due to the polarizers. But here the blueness has been diminished by desaturation as described above.
Interesting aspect #5 is back to the subject itself, in particular how its patterns change over time. Here are three views of the subject that were shot about 1 day apart. The last view is from tonight, just a few minutes ago. In addition to being very dark, the wing covers are starting to soften and dimple, so I'm expecting that very soon now I'll have an adult moth to look at. This seems like a pretty normal sequence for moth development, but I've never followed it this closely before. I'm very interested to note how the basic geometry of the wing patterns are laid down early, and are quite obvious, with the pattern then filling in with increasingly pigmented scales.
And finally, interesting aspect #6 was a reminder of just how confusing things can be for a new user. I do most of my work on Windows. But I shot and processed these stacks on an iMac with 5K display, partly because that machine was conveniently located and partly as another end-to-end test to check out the latest build of Zerene Stacker on a high dpi Mac display with Apple's current O/S. Everything was going along just fine until I decided to press the little green "maximize" button so as to use the whole screen. To my surprise and horror, the main Zerene Stacker window suddenly became so large that the app's top-of-screen menu bar disappeared, along with the resizing buttons. Argghh! Hung! I could not figure any way to do a controlled exit. I finally figured out how to bring up a macOS Force Quit menu, which allowed me to kill Zerene Stacker and regain control of my computer. Clearly some horrendous bug had been introduced with JRE 10 (Java Runtime Environment), and I had to figure out how to work around it. But after some web searching to see if anybody else had reported this, I gradually realized that in fact the observed behavior was actually a feature, not a bug. Several years ago Apple changed their user interface spec so that the green button that used to mean "maximize" was now recommended to mean "full screen" by default. The JRE had finally gotten around to implementing that recommendation. It's completely normal for all Mac applications to lose their menu bars and resizing buttons when they go to full screen mode, but those can be easily retrieved by just hovering the mouse at the top of the screen for 1/2 second or so. That part is implemented by the JRE also, so in the end, everything was fine except that I had not known the proper gesture. I suppose I should be embarrassed to tell this story, but I'm not. The world is a very complicated place, and I only know a little bit of it. Lessons learned, reminders heeded.
All images shot with Canon T1i camera, Mitutoyo M Plan Apo 5X NA 0.14 objective with Canon 100 mm f/2.8 L IS USM macro lens used as tube lens to give 2.5X magnification on sensor. 40 micron focus step, stack lengths about 80 frames each. Synthetic stereo, +-3%. All images PMax, retouched from DMap to avoid starbursts around bright debris.
I hope you find some part of this interesting also!
--Rik
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