I have 7 different lenses in front of me that are good candidates for doing macro photography. The game here is to try them all and see which of them gives best results. Anybody with some scientific training will point out that this is statistically invalid. I am making one test image per lens and using just that to guide my decision. My real worry in that regard is that my setup is decent, but not ideal, and there is potential for vibration to spoil an image and for me to blame the lens. But bearing this in mind, this is a start.
I am shooting off the stand described in my previous article. I know the camera clamp wiggles, and I intend to machine a new piece to replace it. I am using my Canon 5Dii in liveview mode. This his two immediate advantages. First of all, the mirror stays up all the time in liveview mode, eliminating a source of vibration. Second, it is wonderfully easy to do an excellent job of focusing using liveview. I can punch the zoom+ button on the camera and get a 5x zoomed view on the camera viewfinder, which allows a much much better critical focus than trying to use the optical viewfinder. There is even a second zoom level of 10x available, but so far I have not felt compelled to use it. The 5Dii does capture gigantic 5616 by 3744 pixel (21 megapixel images), which allows for a lot of image cropping.
Using liveview, especially with the 5x zoom active, it is quite clear that I significantly bump the camera when I trip the shutter. I am using the cameras 2 second delay feature to let this vibration settle down, but I would much rather be using a remote release (and to improve my stand).
Even on a concrete slab and with the heavy stout table I am using, I can see that when I bump the table I get image motion. I even can see image motion when the air conditioner kicks on in the room (it is directly behind and above the table with my setup). This is a surprise, but underscores the need to have a really sturdy setup and take every step possible to avoid vibration.
The lineup of lenses is as follows:
My test subject is a specimen of Linarite from
the copper level, Cwymystwyth, Ceredigion, Wales.
I am providing this photo of the mount for orientation purposes
and to provide an idea of scale for the photos that follow.
It is mounted in a "standard" althor size micromount box,
so the image width in this shot is about .82 inches across.
(This image was taken with the MPE-65 at the 2x setting, but
we are getting ahead of ourselves).
OK, now for the test images. I show the full image (reduced to 800x533 pixels for the web) and alongside of it a section of 800x540 original pixels cropped out of the original image with no resampling of any kind. I chose an interesting area with a group of radiating crystals, as would be a typical subject of that might be a topic of discussion. Take a look at these images, but don't miss reading my conclusions and comments after all the images.
The specimen being photographed is about 0.40 inches (10mm) across.
The area I cropped out is about 0.0625 inches (1.6mm) across.
Nikon El-Nikkor 50mm/f2.8 enlarging lens, f/11 (above or left)
Nikon El-Nikkor 50mm/f4.0 enlarging lens, f/11 (above or left)
I am pretty sure this image was no well focused for the area cropped and enlarged.
Schneider Componon-S 50mm/f2.8 enlarging lens, f/11 (above or left)
Canon 50mm/f2.8 macro lens reversed, f/13
Elgeet 25mm/f1.9 video lens, f/11 (above or left)
Canon MPE-65mm macro lens at 3x, f/11 (above or left)
Canon MPE-65mm macro lens at 4x, f/11 (above or left)
Leitz 10x microscope objective
The big surprise is the little Elgeet 25mm lens (actually labelled 1 inch, f/1.9). It performs as well as or better than any of the lenses, and was a dirt cheap ebay buy. Also, given its 25mm focal length, I can get more magnification from it at a given bellows extension, which is another plus. Elgeet was an outfit in Rochester, New York making video camera lenses in the 1940's and 1950's with nearby companies such as Bausch and Lomb and the like. Elgeet, I am told was taken from the intials of 3 men who formed the company which were L-G-T.
The other champ is the reversed Canon 50mm/f3.4 macro lens. It performs very well.
My fancy MPE-65 Canon lens is no slouch, but it was no bargain either. It is an EOS lens, so I can control its aperture from the camera (or computer link someday). It is more of a pain to use with my current setup than any of the other lenses. It can only be focused by doing a gross adjustment using the camera clamp and then misusing the "power" adjustment to get critical focus. This does work to good precision, but the right way to do things would be to add a precision focusing rail. All of the other lenses mount on the bellows which has an integrated focusing rail, which is quite convenient.
The Leitz 10x microscope objective is a late addition. It came from a surplus biological microscope (transmitted light) that I had sitting around, and I quickly mounted it by cutting a disk out of a sheet of cardboard. It has no diaphram, so there is no choice but to use it "wide open". It does pretty doggone well, although there is noticeable vignetting (it was not designed to project a wide cone of light). It would clearly benefit from focus stacking software. If does have a very close working distance (about 5mm), but it was not that hard to get light on the specimen, as you can see.
Tom's Mineralogy Info / tom@mmto.org