In the past, I also owned the 25, 40, and 63mm versions of the Zeiss Luminars, which I used on 35mm film and also on my 23 Technika. They worked well, but I sold them after moving to digital and discovering other alternatives (although I do have occasional regrets
ChrisR wrote:I was thinking of something like this, occasionally on ebay (one currently):
Nikon CFI 2X Plan APO Objective, Nikon Part Number MRD00021.
Numerical aperture of 0.10 and a working distance of 8.5mm.
I saw that objective also, but that working distance looks a little short at that magnification, especially for such a large-barreled objective.
However, it inspired me to try my Mitutoyo Plan Apo 5/0.14 at 3X (7.87mm horizontal image field on my 23.6mm sensor), using a 120mm Apo Macro-Sironar as a tube lens (it was all I had on hand at that focal length). This combination gives an effective aperture of approximately 11, and a comfortable working distance of 34mm.
I took approximately 30 images at 25μm steps, stacked them in ZS PMax, and then gave the stack slight Levels adjustment and USM sharpening before posting.
Queen (Danaus gilippus) androconial patch at 3X, Mitutoyo M Plan Apo 5/0.14
Center crop (900x450 pixels)
Corner crop (900x450 pixels)
These are the crispest images I've produced at this magnification, although there may be higher resolution alternatives (like the objective described by Chris). I'm especially pleased with the performance of the Macro-Sironar as a tube lens, since it is optimized for 1/2 life size rather than infinity. (I also tried using a 105mm enlarger lens, to see if I could get an even lower magnification, but the corners vignetted slightly). I was going to run some comparative tests with a few other lenses I usually use at this scale, but that can wait until another day . . .