I use a reversing ring together with a 50 mm lens in order to take macro photographs. The ring allows you to attach your lens to the camera body backwards. A 50 mm lens provides good magnification. The size of the picture will be about 7 by 5 cm. If you want greater magnification you can use a 35 mm lens which provides an image of about 1.75 by 1.25 cm. In order to focus you have to adjust the distance between the image and the camera. For the 50 mm lens, the distance from the front of the lens to image is about 10 cm. The 35 mm lens will have to be closer. This makes lighting a bit difficult. The depth of field is quite shallow so you have to take care to make sure that the camera body is in a horizontal plane with respect to the coin. Otherwise parts of your image will be out of focus. Also, the image on the edge of the picture tends to be out of focus. You can reduce this effect by closing down the aperture.
Proper lighting is one of the biggest problems. Many people
suggest to use two
light sources on either side of the coin to ensure even lighting.
If the coin is shiney and you use only one light source which is too close,
you will have the problem that the one side of the coin will be over
exposed while the other side will be under exposed.
A polarizer filter should help to reduce the relection although I've
never tried this. The degree of polarization is angle dependant so
perhaps the polarizer won't help so much if the light source is at
90 degrees. Remember Brewster's angle?
I find using two lights has the effect of removing contrast. With
one light the raised/lowered edges will create some shadowing which can
improve details of picture. I've used a single light source (halogen desk lamp)
with a piece of white paper taped to the light housing in order
to difuse the light. You can move the lamp away from the coin to reduce
localized reflections. The lamp I use is quite
manoverable and I try to position it as close to a 90 degree angle to the
plane of the coin as possible. You may have to adjust the light source
to get the best effects depending on the coin, whether it is copper,
silver, toned etc... You can see the effect by looking through the
viewfinder and moving the lamp around.
James Grasso has the following suggestion.
"I've been doing some experimenting found that if you use 2 blue lights
(240w) at 45 degree angles you can get rid of alot of the glare."
I tried several exposures where I varied the f stop. The negatives taken with the aperture wide open looked fuzzy and out of focus. Better results were obtained by reducing the aperture some what (Note this applies to the reversed lens configuration). If you look at a piece of graph paper you can see area which is focussed. Try closing the aperture and you can actually see the edges come into focus. You may have to adjust the aperture depending on the size of the coin in order for the edge to be in focus.
Pictures were taken using Kodak TMAX 100 ASA film and developed using Tetanol's Ultrafin plusdeveloper. The developer comes in a 0.2 l bottle which was diluted 1:4. Delevloping time was 18 minutes @20 degrees C with agitation every minute. I've tried Tetanol's Ultrafin liquid diluted 1:20 to develop TMAX 100 film but the results were not as good as with the Ultrafin plusdeveloper.
The pictures were printed on Ilford multicontrast paper with number 2.5 - 3 filters.