Photography lenses are typically designed for operating in the human-visible ~420-680nm range. Within this range the lenses have good transmission, and control for chromatic aberrations (e.g. the red, green and blue channels are all in focus).
UV photography ideally requires a lens which has transmission down to about 300 or 320nm (deeper than this the sun’s emissions are so low it is unlikely to be ecologically relevant to almost any animal). It should also hold focus between the UV and visible range, and control for other types of aberration. These place extreme difficulties on lens manufacture. Few types of optical glass transmit in the UV range well (e.g. fused silica and calcium fluoride), but these glass types tend to have very similar refractive indices and Abbe numbers, meaning it’s difficult to control for various aberrations. Add to this the requirement to hold focus over an even larger spectral range than a standard lens and things get very tricky.
Recommended Lenses (empirical imaging has no affiliation with these suppliers):
|Jenoptik/CoastalOpt 105mm and 60mm UV-VIS-IR||These are expensive, but fairly good UV lenses. Under some photography conditions they suffer from internal reflections and “hot-spots”, which must be eliminated before a photo can be used.|
|Nikon UV-105||Company7 is selling these lenses. We have not been able to test them ourselves, but they have an excellent reputation in the UV community.|
|Nikkor EL 80mm||This is a second-hand lens, produced in the 1980s for dark room photo enlargement. Note that only the older, metal-body version works well (this has chrome detailing and no plastic on show). This lens typically goes for about £60-90 on ebay. It happens to have excellent transmission down to about 320nm, and has almost no focus shift. Being an enlarger lens it has no built-in focussing function. To use this lens on a standard camera you will need: an M42 adapter, an M42-M42 focussing helicoid with a range from 25-55mm (or a bellows), and an M42-M39 adapter ring. Nikons have a deeper back-focal-length than other systems, so a shorter helicoid is required for a Nikon camera to focus on infinity. In total these should cost about £50, and are readily available on Amazon/eBay/AliExpress.|
|Novoflex Noflexar 35mm||This lens was produced in West Germany in the 60s-70s, and comes up on eBay occasionally. It has good UV transmission and holds focus well enough that no focus adjustment is necessary between visible and UV photos. It is the widest-angle lens suitable for UV photography that we are aware of. This also makes it the best option for macro photography (the lens can be reverse-mounted for >1:1 enlargement of small samples). The lens is avaible with different mounts, the recommended mout is the M42, which only needs a readily available adapter for use on almost all modern cameras (though Nikon DSLRs will not focus to infinity)|
|Standard Lenses||Modern “standard” photography lenses can be used for UV photography, however they tend to suffer focus shift, and have poor transmission (typically not much transmission below 360nm, which is not ideal for many animals which have peak UV sensitivity in this region). As such they are not recommended.|