El Nikkor F/5.6 105mm Enlarging Lens

Something must be wrong with the lens. The 105EL is one of the better enlarging lenses, technically better than the 75EL. It should give a result that is nearly as sharp as a 105VR Micro-Nikkor in the middle, and sharper on the edges at equivalent apertures.

Is it clean and clear all the way through? If you shine a flashlight through it do you see any haze, lots of dust, fungus, etc? Could the lens be loose on the mount, or one of the lens elements be loose and moving around when you take the picture?

Your pics look like they are just a bit out of focus. The whole surface of the coin is out of focus, so it's not a field flatness issue like would be the case if it had been disassembled and reassembled incorrectly. Does your setup have sufficient travel to focus properly?

Can you post a focus sequence, ie at f/5.6 focus a little above the high points of the design so all is a bit out of focus on the high side, then directly on the highest points of the design, then on the lowest areas of the coin surface, then a little lower so all is a bit out of focus on the low side? These 4 pics may help with debugging.

This image was taken with a 105EL, so I know in general the lens should be capable of good results:

Maybe it's obvious - and I'm missing it - but are you shooting "raw" pix of coins via this lens attached to a camera body (4x5 plate film? film camera? digital camera?), or are you projecting pix via film images onto enlarging paper?

I agree that the images are slightly out of focus, and of course if you're shooting film images, the original setup could be to blame, or if digital, the focal plane of the lens might be just far enough to project an out-of-focus image onto the imaging apparatus but in-focus on your screen and eyepiece.

Just a guess:

I note you're at ISO 200 and 1/6sec exposure. You gotta speed up that exposure and get more light onto the coin. By comparison, rmpsrpms' Lincoln image was shot at 1/60 with ISO1000, which will gather a heckuva lot less light than ISO100 at 1/6.

Go to ISO100 to minimize the possibility of noise, hood the lens in some fashion so that only light coming from the coin reaches it, and get some more candlepower into the setup.

Don't forget, though, you're learning on the most difficult of all possible coins - lustrous silver.

Here's your last image after 30 second in the Gimp:

As you can tell from the image data and from previous comments on other threads, I am much more conscious of camera movement causing problems with resolution than I am on light gathering. I am even considering moving away from Nikon and toward Canon due to their Electronic First Curtain Shutter which reduces effects of shutter vibration. Nikon's Live View reduces the mirror bounce issue, but there is still some latent vibration due to the shutter itself.

Sidekick-CA, what camera are you using? If Nikon, are you shooting in Live View? Since the problem got worse with a longer focal length lens, this points toward camera shake as at least part of the problem. Longer lenses are more prone to camera shake issues than shorter lenses due to the longer working distance for same magnification (remember geometry class?). I have seen this effect on my setup going from a 105EL to 135EL and then to 150EL. I have never been able to get as sharp an image from the 150EL as the 105EL, even though technically the 150EL is superior. Whenever you have a clear image in the viewfinder or on the Live View screen, and your final image is inferior, camera shake is the most likely culprit.

Because of the above, and contrary to popular wisdom, I always recommend going with the shortest lens you can get away with. You need to be able to get proper lighting onto the coin, but there are many ways to do this even with short working distances. I find that lenses like the 55mm Micro-Nikkor are a bit too short to be flexible enough with lighting, making it hard to take advantage of such a superb lens. they also shorten focal length at closest focus (as do most modern Macro Lenses) so the effective focal length when taking coin photos is even shorter. Enlarging lenses can't do this, so you will likely notice your working distance is much longer on a 105EL as compared to a 105VR for instance. The 105VR is more like a 75mm lens at 1:1.

I am also concerned that you can see haze in the lens without shining a light through it. This is likely at least another part of the problem. If you like, you can send the lens to me and I can troubleshoot it for you. Is the lens the older or newer version? The older one has a chrome-plated mount and takes 34.5mm lens cap. Newer has all-black plastic casing and takes 40.5mm lens cap. I've found image quality to be similar on both, but the older ones are easier to clean.

It occurs to me that I didn't word some of my last post cleanly enough; I've edited it slightly as a result. My main interest in asking you to go to ISO100 was to minimize any possibility of noise, and sort of edge you in the direction of maybe too much light instead of too little.

Even going to ISO800 won't improve that 1/6 to more than 1/20, and every stop smaller of aperture costs you a step of slower exposure. I wouldn't take a Digital Rebel above ISO400 - noise is really noticeable at ISO800 - and I've always tried to stay at ISO100-200.

You can gauge your setup's susceptibility to shake, both from the camera operation or external influences, by putting it in live view or equivalent and giving your setup a bump. The more things wobble around, and the longer they wobble, the worse off you will be. Even if you just sit and watch the image on screen or on a monitor, you will see occasional and random movements. You need to be at 100% magnification to see this clearly. These small movements really mess up the image when long exposures are used, and are a form of noise in the image just like shooting at High ISO. I can't tell you what kind of problem your setup will have for a given lens length, only that the shorter the working distance for a given magnification (ie shorter lens) the fewer problems you will have with this "motion noise". And for a given length of lens, the more you bolt the setup together so nothing can move around relative to anything else, the better.