World's Best 1:1 Macro Lens

I've never had good luck with axial lighting, at least not on its own. There are a number of ways to achieve it but almost all of them have negative impact on image quality. Since axial systems are usually fairly "small" in nature their illumination is highly specular, and creates a lot of hot spots on top surfaces, and by definition does not light edges well so creates excessively emphasized shadows around the design elements. And it only works for raw coins, as a slab will reflect the light directly back to the sensor and create massive glare.

A better alternative may be ring lighting. It's much easier to set up, doesn't get in the way of the image path, and can be adjusted for height to give a wide range of illumination styles. If there is any interest I can take some shots with ring lights on that same coin to compare results...Ray

No worries, I actually just bought a new ring light and this gave me the excuse to set it up. And I am glad I did, because it's giving a better presentation than the ones I have tried before.

Here is what the ringlight looks like. Notice this one has 12 individual sources spaced 30-deg apart. Most ring lights are a continuous band of fiber optic. However, new ones you can buy today are usually LED-based, with 24 or 48 or more separate LEDs. Some have brightness controls, and some have the ability to turn off parts of the ring if you want to emphasize light from a certain direction. For the ones like I am showing below, you also need a fiber optic illuminator to connect them to. At this point, if you are interested in getting one, I'd recommend an LED one rather than a fiber optic one, just because they are probably longer lasting and are definitely simpler, though you need to find one with good (not too much blue-bleed) color index.



Here is the ringlight mounted to my setup:



And here is the same 57D Lincoln as before:



Now, it's not just the ringlight that's changed, this is also with a different lens. Actually, this was taken with the World's 2nd Best 1:1 Macro Lens, the Rodenstock Apo-Rodagon D 75/4 M 1:1. It's an amazing little lens, and much more economical (and available) than the Printing Nikkor.

Most ringlights give continuous illumination, so the apparent size of the source is infinite, and thus don't bring out much if any luster. This one, with the 12 individual elements, seems to bring out a good amount of luster in the image! This bodes well for the new crop of LED ring lights, though it probably means it's best to pick ones that have fewer LED's rather than more. They are making them with more and more (I've seen ones with 148 LEDs!) to simulate the continuous band of fiber optic on most ring lights. This makes them less useful for coin imaging. But perhaps there are some with fewer LED's that I'll need to check out.

SuperDave...Glad to introduce you to the 75ARD1! I too was shocked when I saw the difference between the 95PN, 105PN, and 75ARD1 vs the crop of standard, dedicated macro lenses. Bottom line is that true Apochromatic correction is a must-have for ultimate sharpness and color fidelity, and lenses need to be optimized over a narrow magnification range to operate their best.

Apo lenses have some strange qualities. When adjusting focus in and out, they simply go in and out of focus. No image distortions, no red/green shifts from chromatic aberrations, nothing unexpected. Most of the time this behavior is not noticeable, but do your critical focusing in live view at 100% magnification and it becomes much more obvious!

Another interesting observation when focusing these lenses is that apparent depth of field is reduced. When lens aberrations compromise the image, it is harder to discern when the subject is actually out of focus. With many lenses you can be significantly out of critical focus before the image appears worse than it was at critical focus. The effective circle of confusion is larger due to the blurriness of the image caused by the aberrations. But when the aberrations are fully corrected, the effective circle of confusion shrinks and critical focus is harder to achieve. For the 95PN, 105PN, and 75ARD1 I find that even at relatively small apertures, critical focus range is very narrow. Hopefully this explanation causes no "confusion" ...Ray

DVCollector...it's actually amazing how good a result you can get with simple setups! I've been shocked by the quality of the photos being taken by point and shoots and even mobile phones.

Over time I've heard people describe certain lenses, especially high quality dedicated macro lenses, as having narrower depth of field compared with other lenses. The standard answer these posts get is that depth of field depends only on the effective magnification and effective aperture, basically telling the poster he was wrong and that "it's all physics". But then I saw the effect myself, I realized that in each case of so-called "narrow depth of field" the lens being criticized was of higher quality than the one with better DOF. The explanation based on aberrations suddenly made sense and correlated theory with observation, ie in the end it really is "all physics".

Noting the extra length of the whole assembly brings a question to mind - what lens-sensor distance does a lens of this type require?

I haven't owned many toned coins, so never really got around to refining my axial technique. I worked a bit with one, though, and determined that optimizing the light source to the technique would provide pretty nice results. I'm thinking something close to a coherent beam of about twice the diameter of the subject, maybe a little greater. Possibly two, on goosenecks, so the angle of attack can be varied to equalize illumination over the face of the coin. Axial lighting doesn't have to be absolutely perpendicular to be effective, nor does the glass have to be at 45 degrees - to get the results below, I pulled the light source off-center and tilted the glass until I got what I wanted. This was a dark coin until I lit it properly, and then it exploded.

1853 Half Dime, in a PCGS slab:



Note, I was at the focus limit of my lens to get an image as large as I wished.

I thought I'd share some experiments with axial lighting that I just tried. Here is a recent photo with the new RSD setup:



And here is the same coin with axial lighting:



The axial lighting brings out colors nicely and gives a "look" that is very different from the RSD setup, though it has more shadows. It's actually so different that it's tough seeing they are the same coin! Anyway, this is the best I seem to be able to do with axial lighting alone. I'm thinking of mixing axial with RSD or direct lighting. Maybe a task for tomorrow.

Mark Goodman has updated his review page on the 105mm Printing Nikkor to include his latest comparison graphs. The graphs show that the 105PN is better than the "outstanding" level across a wide mag range. Here is the link to the updated review page:
http://coinimaging.com/printing-nikkor_105.html