Another Coin Photographer Down The Rabbit Hole.

specifically this is the lens I am talking about.
"Schneider Xenar 105mm f4.5 lens #4823282. The subject field of view for a full-frame 35mm image with this lens and the bellows at full extension is 1-1/2" x 1". The distance from the front of the lens to the subject is approximately 8-1/2"."
the lens comes with the bellows.

75mm is about as short as you can go to achieve low enough magnification on typical bellows to frame a Dollar using an APS-C camera. This also means it keeps the setup as small as possible while framing the dollar. Any shorter and you can't frame a Dollar. Any longer and the setup gets bigger to frame the Dollar.

The specific magnification you're talking about is slightly below 1:1 (1-1/2" x 1" is 37.5mm x 25mm) on FF sensor. It's actually 24/25 = 0.96:1, close enough to 1:1 that we can just use it for the calculations. At 1:1, distance from center of lens to sensor is equal to distance from center of lens to the coin, and both are equal to twice the focal length. So for a 105mm lens, this should be 210mm, or 8-1/4". The 8-1/2" they quote is probably due to it not being quite 1:1. So at least the numbers do make sense.

On FF sensor, you will need to have a bit higher magnification since Cents are 19mm diameter. I usually figure on 1.2:1 for Cents on FF, so you will need about 10% longer bellows extension to frame a Cent properly. You will need 15% longer to frame a Dime. Dollars are 38mm, so require a magnification of around 0.6:1, requiring 20% shorter extension.

Remember that the total extension includes the camera register, which is about 44mm for Canon, plus any adapters, as well as the bellows minimum extension.

It's interesting to note that FF sensors actually make these tradeoffs easier, because they require higher magnification (typically 1.6x) to fill the sensor. This means that 75mm is not the "sweet spot" for FF sensor cameras. Typical bellows are around 44mm minimum extension. Adapters add perhaps 15mm, and the register is 44mm, so minimum extension is approx 103mm. This gives a minimum magnification of (103-75)/75= 0.37:1, which can frame a Dollar with a little space around it on APS-C, but only fills 59% of the sensor on FF. The equivalent focal length for FF is 64mm. So even on FF you can't use a 50mm (or even 63mm) lens on bellows for Dollars. I don't know of any commercial bellows lenses between 64mm and 75mm, so 75mm is still likely the best choice, even for FF.

All that said, I have built several setups where 75mm was not long enough to frame a Dollar due to either the bellows being a bit longer minimum length (like Canon Auto Bellows), requirement for more adapters, or using a Nikon camera, which have longer register distance. In these cases I resorted to using an 80mm lens instead, and all worked out, but each combination of bellows, adapters, camera, and available stand height has to be checked individually to see if it can meet a full-range requirement.

You'll find the 105 useful - depending on its' quality, of course - but the size of coin you can image will be limited. Wouldn't hurt a bit to play with it and see what it can do.

Ok. I bought some stuff already. APS-C camera canon rebel XS and this bellows lens combo
http://www.ebay.com/itm/Novoflex-du...em3f4b9c5f7f
and a $15 Omega 75mm f/3.5 El-Omegar Enlarging Lens. I have a very jury rigged stand that I'm not sure is sturdy enough, that's why I'm looking for a microscope stand. So I will have both a 105mm and a 75 mm lens.

Clever stand. It doesn't have fine focus ability, but the bellows you bought does and may be all you need.

Now, the bellows is a native Exacta mount, so requires adapters both ends to be useful. Luckily it comes with the required adapters (the EXLEI converts Exacta to 39mm Leica mount) so you are technically set, but those adapters add a lot of extra extension. It's not clear if the bellows will have short enough minimum extension to work with Dollars using the 75mm lens. You may end up using the 105mm for everything. That's not a bad thing, because the Schneider Xenar 105mm bellows lens is excellent, and is worth the price of the whole auction and then some. In fact if you ever decide to sell it, I will buy it or trade with you.

Even if the 75mm can't frame a Dollar, you may still want to use it for higher mag shots than the 105 can do, if that's of interest.

I ordered an M42 to M39 adapter from Russia a while back and never received it. I did get a full refund but had to wait 4 weeks due to the estimated delivery time. It's too bad because it was a nice (looking) robust adapter but the helicoil style works just fine.

I'll take photos tonight and show you. if there is another ring in there its REAL tight.

My photos don't help but it is all one piece. What I have seen by searching ebay is there is an adapter called EXLEI K which I think is the adapter I would need to connect a 39M thread. Maybe there is a vintage leica thread that is 32.5mm x 0.5?
In any case I ordered a canon FD to EOS adapter and also Canon FD to Nikon F adapter since I also have Nikon gear. The Nikon adapter arrived today so I was able to finally see what bellows macro stuff is all about. I took a few snaps of cents I will try some big coins later today. Should I continue this thread with my pictures or start a new thread?