Coin Photo Setup

I had to re-check...and after readjusting the lighting a bit for better shadowing, I got these images at 1/200sec:

Overall image with Nikon CF 5X Infinity-Corrected Objective on EL-Nikkor 150mm tube lens, resized 1/4X


Detail image from above, cropped 1/2x, resized 1/2x

Once you've seen a few images at this magnification, you can conclusively determine if a coin has been mechanically cleaned, even very carefully. A dip is pretty easy to spot, as well. See how rough the fields of a coin actually are? That goes away instantly the minute a tool is applied to the surface of a coin. Dipping changes the colors on the surface - it requires a bit of experience to see the signs, but they're there.

Yeah, I'm thinking a little Pyrex dish for pre-imaging acetone rinse is in order for me.

OK, next question. Is there anything pre-existing out there in terms of a finely-adjustable movable stage for the X-Y axis, or will I have to build my own?

As it turns out, the 150mm EL-Nikkor used as "tube" lens or "relay" lens on bellows with 5X Nikon CF Plan
objective gives perfect magnification for the Lincoln Cent "Money Shot", the shot that fills the sensor with the
date and MM. Here is the money shot for the 1957-D toner that I use for most of my image comparisons.
Note the dull surface finish that the heavy OBW roll toning causes. I've never seen this before in this much
detail. I really love this combination of lenses!

1957-D OBW-Toned Lincoln Cent, 150mm EL-Nikkor plus 5X CF Plan, 11:00 side lighting, 5-Stack

Here's what it looks like. Bellows is a Pentax Auto-Bellows, M42 and the lens is mounted using a M39-M42 adapter. The Nikon objective is mounted using a M27-M52 adapter. One of the conveniences of this setup is the 150EL takes standard 52mm accessories.

I tried imaging a coin with a lot of luster using the Nikon 5X / Nikon 150mm, and the same coin again with as close a lighting as I could using the B&L MZ7. Here are the two images:

Nikon 5X CF Plan BD Objective on 150mm EL-Nikkor on bellows:


Bausch & Lomb MonoZoom7


The Nikon 5X has a larger effective aperture and required 8 stacked images. The MZ7 required only 5 stacked images. Working distance for the Nikon 5X was only about 7mm, while for the MZ7 it is 80mm (!) which gives a lot more lighting flexibility.

I have a Mitutoyo 5X MPlan APO objective that supposedly has long working distance, but am waiting for a reversing adapter to arrive. I will make the comparison again between the 3 optics when the adapter arrives.

Ray

For this photo, the MZ7 body was set at 5X, with 1x objective and 1.5x multiplier. So there is continuous zoom adjustment available on both high and low side, with up to 7X on high side and down to 1X on low side available, all at approx same working distance. For some reason I can not get the 1.5x multiplier to be parfocal, so some WD adjustment is needed with that combo as height is changed. On the other hand, my 3x multiplier is parfocal, so I expected the 1.5x to be as well.

I have a full set of objectives acquired over the years: 0.25X, 0.5X, 0.75X, 1X, and 2X. These are great for adjusting working distance and mag range. So with this one instrument, I have an effective mag range at the sensor from approx 1:4 up to approx 42:1 (overall range of 168 !!) though of course for a given objective and multiplier combination the range is "only" 7X. WD gets quite large with 0.5X and is massive with 0.25X objectives, but even with 2X is still workable for lighting.

I've never made the comparison of the MZ7 with low mag objectives for a full coin shot versus my "normal" setup. Maybe that's a good activity for the weekend...

SuperDave...Well, getting the full coin image was not easy but I managed to convince the MZ7 to do it.

From the images below, it is clear that the MZ7 is not optimized for ~1:1 magnification. Field flatness is not great, and since its effective aperture is pretty small, diffraction is degrading the image compared with the 75ARD1. I used a ring light for both the images to make the comparison easier. Here are the images:

Bausch & Lomb MonoZoom7 at ~0.8:1 magnification at the D7000 sensor, Ring Light


Rodenstock Apo-Rodagon D M=1 at ~0.8:1 magnification at the D7000 sensor, Ring Light