About a week ago I posted my first attempt at image stacking: a magnified picture of a common sow bug or woodlouse. I have been trying since then to improve my technique and produce a better image. The photo above is my latest attempt. It’s not that I am particularly obsessed with photographing sow bugs—I just wanted to be able to compare this result with my previous attempt (which I have posted again below for reference).
The equipment I used was an Olympus E-620 digital SLR and Zuiko 50mm F1.8 reversed on an Olympus OM auto bellows. A bellows is fitted between the camera and the lens and is used to extend the distance between the lens and the camera sensor, significantly increasing the magnification of the image. The bellows and 50mm lens are both “heritage” pieces. I have had both for more than 25 years—they are part of my collection of Olympus OM system 35mm camera equipment. Unfortunately Olympus doesn’t manufacture a bellows for their digital SLRs, but they do offer an adapter for attaching a modern body to an OM lens (or bellows). You can’t attach a modern lens to the bellows though, which is why I am using a “heritage” lens.
The handy thing about using a bellows is that the entire unit sits on a focussing rail to allow you to move it back and forth to focus the image without changing the magnification. This is important for image stacking as you want each image in the stack to be at the same magnification, but focused on different planes of the subject. For lighting I again used an Olympus ring flash, but I inserted a translucent white plastic cup (with the bottom cut out) as a diffuser between the flash and the sow bug.
I initially took 46 pictures of the sow bug (each at a different focus) and stacked them using Zerene Stacking software. The results were less than thrilling. So I tried again with another series of photos…with the same mediocre results. A third try gave me another poor result. The resulting stacked image just didn’t look right. The softer lighting was clearly better, but the resolution wasn’t what I expected. When I looked at the images closely I could that some areas of the pictures were repeated more than once.
Over the next couple of days I tried shooting with different subjects and kept getting the same result. If you had listened carefully over the past few days, no matter where you live in the world, you could have probably heard me banging my head against the wall in frustration…
After thinking for a bit, it occurred to me that given the depth of field provided by the lens I was using (stopped to F5.6) I really didn’t need to take so many pictures. You see a lot of people use microscope lenses for this kind of photography, and those lenses have next to no depth of field. Therefore a huge number of images are needed to produce a sharp stacked image. But perhaps with my equipment fewer images would resolve the double-imaging problem.
I opened the last group of photos I had taken of the sow bug and deleted every second picture in the stack. Then I ran Zerene Stacking again using the remaining 24 photos. The resulting image was much better, except for a double-image of the antenna on the left. When I reviewed the images I discovered that part way through the stack the antenna had dropped a bit—so in half of the photos the antenna was in one position, and in the other half it was in a different position. Sigh.
Happily I was able to delete the double image of the antenna in Photoshop using the wonderful Clone Tool. I also tweaked the contrast and sharpened the image a bit.
The final result is definitely better than my first attempt don’t you think? But the resolution still isn’t perfect. Somehow the image doesn’t look “crisp” enough. I don’t know if it is the lens or my technique; but given the quality of Zuiko glass, I suspect the latter. I’ll keep working on it.
The technical stuff:
Camera: Olympus E-620 digital SLR
Lens: Zuiko 50mm F1.8 reversed on an Olympus OM auto bellows
Settings: manual exposure (F5.6 @ 1/125 sec)
Lighting: Olympus RF-11 ring flash (manual; 1/8 power)