#2.

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the best performance that I have come across in the 2-3 range is the Canon 35/2.8 bellows. Have to run it with minumum extension to get that mag.

The easy way to figure the focal length (approximately) is to reverse the formula for extension ex = f*(m+1) For a 160 tl (150mm to the internediate image) 10x objective 150 = f*(10 +1) f = 150/11 = about 14.5 mm. That assumes that the principal plane of the objective is at the flange - it's probabl...

A good enlarging lens of >70 mm will not likely outdo a MP-E 65. A 50mm componon-s or APO-componon 45mm should perform virtually as well as a MP-E in that magnification range. It will commonly cost you significant resolution to get more working distance. The componon-S 50/2.8 is an extremely good le...

I haven't stopped the 40/2.8 down. I would like to.

I would like the see if I can remove the lenses (easy to do with some of them) from a similar size componon - leaves you with the aperture housing. May be able to screw in the 40/2.8 into the housing if the same size.

I have a 40/2.8 componon, fixed aperture lens. Not a great performer at f/2.8. Really needs to be stopped down a notch or two. Another thing to consider with running a microscope objective at a lower magnification than designed. If the front element of the objective is smaller than the entrance pupi...

An easy way to clean up color issues in pics is to use the color channels in Photoshop. The R, G, and B portions of the image can be easily separated and the resulting image saved in B&W.

The with using a blue filter is two-fold on a dSLR. 1) There are only half as many blue pixels on the detecter. 2) Put a blue filter on and try to focus the image. I dare ya. Our eyes are not particularly sensitive to blue light, especially in a darkish viewfinder. Green works really well and is eas...

I have one of these 40/2.8's. It isn't my favorite lens. Decent resolution but not particularly sharp. The field isn't particularly flat either. It would benefit from an adjustable aperture.

I have a 45/4 APO-componon that is much better and has an adjustable aperture.

The componon 50/2.8 is the best 50mm enblarging lens that I have tried. Should be mounted reversed. Will need a reversing ring and a step-up adapter that fits the 43mm threads (at least mine is 43mm). If it is one of the newer lenses, you will also need to remove the aperture handle to mount in reve...

My own calculation puts the front principal plane about 10 mm behind the frontmost portion of the lens.

My own testing of the Oly 20, JML 21 and Nikon 10/0.25 lines them up roughly by aperture. From best to worst resolution-wise: 1) 10x/0.25, 2) Oly 20/2, 3) JML 21.

The JML performs very well all-in-all, virtually as well as any 20mm bellows lens. Pretty good for a $10 lens.

I have a BD (same as mitutoyo) to C-mount adapter. In that transition you only go from 26 to 25 mm. The other factor is that the 26 mm BD is mostly open space on the edges anyway to allow for the funky lighting.

nikon also uses a 25 mm mount on some of their newer objectives.

M plan is an RMS mount. (20 x 0.8 )

BD (non-infinity) is a M26 mount (26 x 36 tpi)

That diagram is from Photographic optics by Ray. Big red photographic optics book.