What lens should I use for coin photography? This is a question that I get asked frequently. So, I figured that I would put it down in this article.
Focal length: For coins, I would tend to stay above 100mm. These lenses will offer the best working distance - distance from the coin to the front of the lens. The relatively long working distance will allow for better lighting than short focal lenses. Longer focal length mean better luster and better color. The drawbacks of longer focal length lenses are higher price and less stability. Longer focal length lenses have a more narrow field of view at the same working distance as a shorter focal length lens. This means that any camera shake or vibration will result in more fuzziness in your pictures. To reduce the effects of this, it is best to use a remote release (I got a wired one for $3 on eBay). It is also useful to have a sturdy copystand (or less conveniently a tripod). I have a Nikon 200mm micro and that lens really tests your setup and technique.
Magnification: Magnification is measured in a ratio (size of detector: size of object). Most newer macro lenses focus to 1:1 - life size on the detector. A 23 mm object will fill the 23 mm detector. Many older macro lenses only focus to 1:2 - half life size. A 46 mm object will fill the 23 mm detector. 1:2 macro lenses can be brought up to 1:1 magnification with half the focal length in extension tubes. A 105 mm lens will require 52 mm of extension to go from 1:2 to 1:1. 1:2 is good enough for coins although a boost closer to 1:1 is useful for small coins. You can also use add-on lenses (also called diopters) to get your magnification a little higher. These typically come in +2d (Canon 500D), +3d (Nikon 6T), +4d (Canon 250D), +8d (Raynox DCR-250). A higher number means a greater increase in magnification. The typical rule with using these is to only use +4d and above on lenses less than 100 mm, and less than +4 for 100 mm or greater lenses.
Maximum Aperture: The number after the focal length pertains to the maximum aperture for the lens. Smaller numbers mean larger apertures. Larger aperture mean a brighter viewfinder and easier focusing. Larger aperture means more expensive and a bigger, heavier lens.
Nikon: I have the most experience with Nikon lenses so I will spend the most time here. I will go from new to old in the list. Used prices imply good fully functional condition.
- 105/2.8 AF-S VR micro: ($900 - $1000 new, about $800 used) The most current autofocus 105 mm micro lens. This lens will have full functionality on all Nikon dSLR bodies. VR (vibration reduction) doesn't help you with macro, so leave it off. Autofocus is a little spotty for macro and manual focus works better. 1:1 magnification.
- 105/2.8 AF-D micro: ($400 - $500 used) Fully functional with most dSLR bodies. No VR, but none is needed. No autofocus on camera bodies without an internal focus motor - D40, D60, D3000, D5000 and newer variations. Similar to above otherwise. 1:1 magnification.
- 105/2.8 AF micro: ($300 - $400 used) Some loss of function with most bodies. No VR, but none is needed. No autofocus on camera bodies without an internal focus motor - D40, D60, D3000, D5000 and newer variations. The loss of functionality is pretty minor - some fancy metering and some loss of flash functionality. Nothing major. 1:1 magnification.
- 105/2.8 AIS micro: ($250 - $350 used) Manual focus. Moderate loss of function with all dSLR bodies. Limited to A (aperture priority) and M (full manual) modes - D7000, D200, D300, D700, 800, D3, D4. This is not a problem for me as I use A mode exclusively. Limited to M mode for lower level bodies - D40 through D90, D3000 through D5000 series. The limitation to M-mode means that you will have to set the shutter speed in the camera and the aperture on the lens. the easiest way to get a good exposure with this is to use the histogram on the display - a graph showing the brightness range of the image. Not difficult to use with a little practice. 1:2 magnification.
- 105/4 AIS micro: ($200 - $250 used) Manual focus, limitations as #4 above. 1:2 magnification.
- 105/4 AI micro: ($150 - $200 used) Manual focus, limitations as #4 above. 1:2 magnification.
- 105/4 pre-AI micro: These lenses do not work on current dSLR bodies unless they have been AI modified (also called AI'd). 1:2 magnification.
- 200/4 AF-D micro: ($1600 new, $1300 used). Autofocus. Similar functionality to #2 above. 1:1 magnification.
- 200/4 AIS micro: ($500 used) Manual focus. Similar functionality to #4 above. 1:2 magnification.
- 200/4 AI micro: (maybe a little less than #9 above) Manual focus. Similar functionality to #4 above. 1:2 magnification.
Canon: Canon changed its lens mount when they went to autofocus. This causes some difficulty with trying to use older manual focus lenses.
- Canon autofocus macro lenses: As far as I know, these should all be fully functional on current dSLR bodies. These are called Canon EF or EOS mount. They can also be purchased for a discount used.
- Canon manual focus macro lenses: These lenses will require an adapter to work on current dSLR bodies. They will lose most functionality because of this adapter. As far as I can tell, you will be similarly limited to Nikon manual focus lenses, but you will also lose automatic aperture control. You will need to open the aperture fully to focus and then manually close the aperture via the aperture ring to the desired f/stop prior to shooting the image.
- Nikon micro lenses: You can use Nikon micro lenses on a Canon body with an appropriate adapter. Functionality loss will be similar to #2 above. Doesn't work nearly as well the other way (Canon lenses on a Nikon body) because of flange distance and mount diameter differences.
Sigma: Sigma makes autofocus macro lenses that work on most all lens mounts. They will be fully functional except for possiblr AF issues on current dSLR bodies.
- 105/2.8 macro: ($750 new, $300 used) The newest version of this lens is similar to #1 on the Nikon list. The older version is similar to #2 on the Nikon list. 1:1 magnification.
- 150/2.8 macro: ($1100 new, $800 used) Similar to the 105 with two models. Both will be similar to #1 on the Nikon list. 1:1 magnification.
- 180/3.5 macro: ($600 - $800 used) This is the older version of the lens, but still similar to #1 on the Nikon list. 1:1 magnification.
- 180/2.8 macro: (about $1700 new) The newest version of their 180 macro,again similar in functionality to #1 on the Nikon list. 1:1 magnification.
Tamron: Similar to Sigma in that Tamron offers autofocus macro lenses in a variety of lens mounts.
- 90/2.8 macro: ($400 - $500 new) The current version is fully function on modern and appears to have an internal focus motor so it should work full on all current dSLR's. The older versions will lack some AF functionality (like #2 on the Nikon list). 1:1 magnification.
- 180/3.5 macro: ($600 - $800 new) No internal focus motor, so will act like #2 on the Nikon list. 1:1 magnification.