Nikon D200 Reviewed. UV

People familiar with my style of shooting 'invisible' light are well aware of the fact that I'm partial to UV. So, one of the the first issues addressed with the D200 was shooting UV with my trustworthy UV-Nikkor 105 mm lens. Granted, not many of these expensive goodies are floating around, but some do exist. Togichi Nikon, an industrial subsidiary of Nikon, recently commenced a new production of this lens (now labelled just UV 105 without the 'Nikkor' name engraved, but otherwise identical to the original). You can also shoot UV with a score of alternative lenses; read more about this in my Digital UV and IR Tutorial.

The camera designers don't like UV any more than they do IR coming into their digital contraptions, and for similar reasons. UV has a different focus than visible light and will disrupt sharpness plus contribute to the washing out of colours in sky areas. However, unlike IR, the UV rays are quite efficiently filtered out by pure optical means long before they can reach the imaging chip inside. Thus the optical glass in the lens, bonding substances, and in particular the multi-coating layers, prevent much of the impinging UV to pass through. Of course none of this applies when a dedicated UV lens is put onto the camera. Learning that the D200 possessed a CCD imager, I initially was quite optimistic regarding its potential to do UV. However as events later turned out, this optimism was unfounded.

The D200 follows the trend set by the D2X meaning it is little responding to UV. However, unlike the D2X and more similar to other Nikon DSLRs (D1, D1X, D2H) it records UV mostly in the red channel. The D1H and D70 have useful response in the other two channels as well, and the D2X has mainly a blue-channel UV response.

The UV response of the D200 tested with a filter pack of B+W 403 and BG-38 on the UV-Nikkor 105 mm f/4.5 lens is typically 15 stops under normal daylight. This is an additional 4-5 stops lower than the UV response of the D70. Thus, I would not consider the D200 a candidate camera for shooting UV flower images because of its low UV response. In fact I did try, and you can draw your own conclusions from the images presented below.

Ultra-Violet Peace Lily (Spathiphyllum sp., Araceae) D200 vs D70

D70 f/13 @ 800 ISO equivalency, UV-Nikkor 105 mm f/4.5 lens, Hoya U-360 filter on lens, SB-140 UV flash	D200 f/5.6 @ 1600 ISO equivalency, UV-Nikkor 105 mm f/4.5 lens, Hoya U-360 filter on lens, SB-140 UV flash
The D200 is at least 3.5 stops less sensitive to UV than the D70 when the subject is illuminated by a dedicated UV flash, yet both have CCD imagers. This conclusively points to the 'improved' internal filter pack as the main reason for the much reduced UV response. There are UV "colour" colour differences between the two cameras as well. Any such UV "colour" is just imaginary by definition, but the camera and its imaging chip with the Bayer filter on it do not know this fact, so goes on to produce "false" colours nevertheless. That these faked colours end up different only means the UV response is subtly different across the (R,G,B) channels, a phenomenon very frequently observed when using DSLRs for UV photography.

So, can the residual UV response be put into service for landscape work, such as the case is for the D2X? I've tried, and my conclusion is that there are better ways than this of wasting your time. You are ensured of noisy and grainy images with much loss of detail, and very long exposure times. Direct comparison, as depicted below, indicates the D70 is in this case about 5 stops more UV sensitive than the D200. In addition, the D70 gives lots of image detail as well. I've not done direct UV comparisons against the D2X, but from its known placing versus the D70, it can be inferred the D200 is at least one stop less sensitive to UV than even the low-sensitive D2X.

Ultra-violet Landscape (D200 vs D70)

D200
13 sec exposure at f/5.6 @ 1600 ISO equivalency,
UV-Nikkor 105 mm f/4.5 lens, Hoya U-360 filter on lens
(The white stuff covering the ground is snow, a common substance of my neck of the woods, and a good reflector of UV light)

D70
0.6 sec exposure at f/5.6 @ 800 ISO equivalency,
UV-Nikkor 105 mm f/4.5 lens, Hoya U-360 filter on lens

So, although some UV response of the D200 is evident, it is not a suitable candidate for a UV camera. For people less engrossed in ultra-violet than me, the low UV response does mean landscape motifs with lots of blue skies are less likely to get washed-out sky colours. One loses, another wins.