Before I answer the question, I have some background explanation...
This is a 4x-reduced image from the original 4928x3264 (Nikon D7000) to 1232x816, and then cropped to 800x800. The reduction process increases the apparent resolution of the final image and allows lower quality (and even high quality) lenses to look better.
Note however the entire coin looks sharp, not just the center, so this is a testament to the T86 flatness of field. The larger you make the image on the sensor, the more the lens aberrations and flatness of field come into play so even a 4x reduction can't produce a nice image when the lens doesn't focus well at the edges of the coin, or produces off-color.
This shot was taken at f/8. Notice the background is reasonably clear, which would not be the case at f4. This reduces aberrations and also helps with field flatness since any flatness issues are mitigated by the increased DOF of the smaller aperture.
The reason for stating the above is that in this situation (4x reduction and f/8 aperture) the difference between the Printing-Nikkor and the T86 is very small. Printing-Nikkor color may be a bit more accurate, but the T86 is actually quite good. I see no color fringing when focusing with the T86, so it is very well-corrected.
The difference between the lenses becomes apparent at smaller apertures, with no reduction. So for example, if I took the same image at f/4 with both lenses, and instead of reducing the images I looked at fine details on the coin such as the date and mintmark area, the Printing-Nikkor would be sharper than the T86. Also, if I critically-focused both of the lenses on the center of the coin (cheekbone) the Printing-Nikkor would be better focused and sharper on the rims of the coin than the T86. And finally note that the Printing-Nikkor can go to f/2.8, so resolution can be increased even further, though at that aperture you need to focus stack to get good sharpness in the final image. There are always tradeoffs!
You can see extensive test results for the 105PN on Mark Goodman's coinimaging.com website. He has been testing a lot of lenses and has a very methodical and of course numismatically-oriented approach. Here's the link:
http://coinimaging.com/Lens_tests.html That brings me back to the whole point of this thread: you don't need to spend $2500 (or even $250) on a Macro lens for coin imaging for Web publishing...this $39 T86 lens can produce a remarkably-sharp image at the 800x800 image size that is standard for posts on this forum and many other similar lenses are available with excellent performance.
Posted 11/10/2011 01:33 am
, I've been wanting to try this lens out on my bellows...Thanks
Gene
