Medford, (~25 miles east of Philadelphia, PA) Burlington County, New Jersey, USA
Upon finding BugGuide, I wanted to share images of the magnificent detailed small beetles I could see when viewing them under magnification through my Stereoscope. I could see intricate detail with excellent depth of field with magnification between 6 to 40 power on subjects which mostly ranged only 2 to 7 mm. The problem was that with my present equipment and budget I wasn’t able to produce images that seemed close to the clarity and “showiness” that I could see with every gaze through my stereoscope.
The Failed Attempts:
I had a Canon Powershot A610 (midsize point-n-shoot) (and later A640) to work with, which has excellent macro focusing capabilities (right down to zero cm) and excellent resolution. So the logical first step was to simply point the camera through the stereoscope’s eyepiece, and capture the same wonderful scenes as my eyeballs. This did require the lens to be zoomed to max telephoto (4x) to somewhat match the camera’s field of view of that of the eyepiece. While the resulting images captured some of the detail, they were not as sharp as what I could see. And they suffered greatly from lack of depth of field, clarity, and a few other things. (the before)
At least two very acceptable solutions were known to be available, but neither came close to fitting my discretionary spending budget. Canon’s MP-E 65mm 1x-5x dedicated macro seems to be the lens of choice for BugGuider’s smallest subjects, and is especially suited for live subjects, unlike some other options. But at ~$900 for the lens, ~$600 for the accompanying MT-24EX twin macro flash, and say ~$600 for even the most basic Canon DSLR body, quickly adds to over $2k, which is more than I could afford.
The other common system known to me that clearly produces images of the quality I desired or better is the Automontage system
. The system consists of an optics setup similar to a stereoscope’s with a digital camera mounted onboard to capture the images. The whole setup is computer controlled to both capture images directly from the camera, and mechanically step the focus of the optics. Images are captured at each focal setting, and the resulting image series are “stacked” by software to yield a composite image with depth-of-field much greater than any of the single images alone. These systems seem to the purview of universities and institutions, I assume mainly due to price. But I have actually no idea what they cost. See some BugGuide pictures/info on them here
, and check out Jeff Gruber’s stunning results in his posts.
Eureka! The Solution:
The solution for me (both optics and budget) turned out to surprising simple. And in the end did not involve a Stereoscope. After reading several web articles on “optic setups for macro”, and most designed for non-SLR cameras, I settled on the “reverse mounted lens” technique (see an excellent explanation here
. It’s actually been around since before digital cameras and was used to produce images similar to those of Canon’s MP-E 65mm. All you really need is a point-n-shoot similar to mine and an old “fast” SLR lens.
My basic parts list includes:
Canon Powershot (A640 in my case, but almost any A, S, or G series will work) ~$250
(must be a Canon Powershot for firmware availability)
Canon CDHK firmware hack for focus bracketing (freeware)
Powershot lens adapter sleeve, normally used for auxiliarly lens ~$10
fast (f1.4) 50mm SLR “prime” lens (used from e-bay) ~$50
various filter and reversing rings to mount 50mm lens to lens adapter ~ $20
Stereomicroscope stand with fine focus (other setups possible) ~$100
Halagen spot lights or fiber light source ~$120
2x telephoto auxiliary lens ~ $80
Stacking software (freeware available)
The 50mm SLR lens is reverse-mounted to the Powershot’s lens adapter sleeve, which is of course mounted on the Powershot using the standard attachment lock. The rear of the reversed SLR lens is now pointing at the subject / bug. The working distance is now the same as the old SLR’s film plane – about 35mm. The Powershot must be zoomed out to 4X max (29mm on my A640 and most others. The S series can go much further), to best match the 50mm lens’ field of view. You gain magnification as the focal length of the Powershot increases in proportion to the focal length of the reversed lens. A very fast lens is needed (low f-stop) to provide wide enough glass. And several articles have explained why 50mm is optimum, as opposed to wider angle lens (which generally don’t come as fast anyway). With the Powershot at 4X and a reversed 50mm lens, the resulting usable image is about 13mm, and covers about 75% of the length of the frame (or about the full height). The corners are all blurred and a little dark, but the final images will be cropped anyway. Adding a 2X tele auxiliary lens between the Powershot and the reversed 50mm doubles the ratio of focal lengths (just like it should), and results in about a 5mm usable image, covering about 50% of the length of the frame. Again, cropping will eliminate the blurred edges. I’ve briefly tried using a 3X tele aux lens (higher focal ratio and magnification), but initial results were not favorable. But I have yet to apply this technique with the “superzoom” S series, which wouldn’t add all that tele aux glass. See dpreview.com
for great info, specs, and reviews on Powershots, past and present.
All this glass gives great magnification (small bugs spanning a significant percentage of the frame), but with the Powershot zoomed all the way out (and worse when the tele aux is added) depth-of-field can shrink to a millimeter or less. I overcome this by taking multiple images of the same non-moving subject at very slight different distances. There’s several ways to accomplish this: move the camera (like the Automontage systems), move the subject (a compound microscope stage might be used for this), or change the focal setting of the camera. I use the last method. The Canon firmware hack, CHDK wiki
, allows among other possibilities, the ability to script or command specific manual focus settings. You first load the replacement firmware on the memory card, and then write scripts which execute when you push the shutter button once. I use a simple script to manually command the camera to focus to one distance, take a picture, then focus to the next slightly different distance and take another picture, and so on. You can dictate the size of the distance steps and the number of them, or just about anything you want. Through mostly trial and error, I’ve found a stack of 15 different focal distances is more than sufficient to overlap the DoF for any bugs, with or without the 2X tele. Start near minimum focal length, and step out. You quickly reach diminishing returns well before approaching infinity. I get the focus close using the Stereoscope stand to hold the camera setup, and then just hit the shutter release and stand back while the script snaps off the images. Then it’s off the darkroom, or rather the computer, to download the images, stack them together, and crop and tweak the final composite.
While the results are clearly not as good as many of the BugGuide posts using different equipment, what I found got me to my desire of being able to share images comparable to what I can see through my scope. :)