Variety Coin Photos

I don't like the rainbow-sparkle effect from undiffused Jansjös. I guess I'll have to experiment some more.

Yeah, I have a T3i which has the same sensor as a T2i. But I don't think it's an artifact of the sensor (at least, not entirely). I can see the rainbow-sparkle effect with my bare eyes with coins (and other metallic things) held under the Jansjö lights. Sometimes you can see the same effect to a lesser extent in strong sunlight, so I think it has something to do with harsh, highly-directional light interacting with fine surface features.

If you really want to do a good job with variety shots, I recommend using a microscope objective. The setup that works best for me is:

M42 extension
M42-RMS tapered adapter
4x or 5x Microscope objective
Half Ping-Pong ball diffuser

Total length of camera register (44mm for Canon), extension, and tapered adapter needs to be 150-160mm. The tiny diameter of the microscope objective allows you to get light in very effectively using the ping pong ball and one or two Jansjos. If there is any interest I can publish a pic of the setup.

Here's a pic of the setup I'm currently using. The objective is a Nikon P4/0.1, which is a very affordable objective. You can't really see it in the pic due to the ping pong diffuser but you can see its upper knurling and red indicator ring. I mounted the ping pong diffuser onto the objective itself but you also have the option of mounting it using the RMS threads since this objective is quite small. A small Nikon M5 or other small objectives from Olympus, etc will work well for this. The NA=0.1 objectives are most common at this magnification, and are equivalent to infinity f4 or effective f20. This is far from the best you can get at this magnification (NA=0.2 are available) but even at f20 you will need to do 5-10 image stacks. With the NA=0.2 objectives you would need typically 30 image stacks and the result is only slightly better for web publishing.

Exactly...you can move the light(s) around to shine from whatever direction best emphasizes the shadowing on the variety. You can also use a ringlight and the ping pong ball will diffuse it nicely.

P4 0.1 is what is marked on this objective. It means Plan 4x with Numerical Aperture 0.1. The objective does not state the tube length or if it needs a cover slip, so I believe it is assumed to be 160mm and no cover slip, ie 160/- as you said. Any tube length is OK, but I recommend avoiding "infinite" objectives (they have infinity symbol/cover slip thickness). You also want to avoid anything requiring a cover slip. All finite metallurgical (M) objectives are OK to use. So acceptable types would be marked:
P4 0.1
Plan 4 0.13
4x 0.1
SemiPlan4 0.15 160/-
etc...



Ray

Yes, most are designed for 200mm lenses, though some are for 180mm. You can use most any lens as a tube lens. This is fairly convenient for setups using a long macro lens but otherwise it's a completely different setup. Quality is excellent with some of the infinite objectives, though. I own a 5x 0.14 Mitutoyo that is apochromatic and gives superb results, but I never use it since I have the bellows setup and it's just not convenient...Ray