|Nikon D200 Digital Camera Reviewed|
|by Bjørn Rørslett|
7. Infrared (IR) photography with D200
One pleasant surprise with many of the digital cameras is their ability to record useful imagery outside the visible spectrum. Typically, the sensitivity to near-IR may be sufficiently high to allow IR photography not only in bright sunlight, but also under less well illuminated conditions. This is good news for any experimentally inclined end user, but bad news for the camera manufacturer. Initially, we would expect a CCD-based camera such as the D200 to be more responsive to IR than the CMOS-based models, but is this really the situation here? Read on to learn more.
The camera designers expressedly don't want IR to enter their cameras because IR will reduce perceived sharpness, make skies look washed out or experience colour shifts, produce blotched facial rendition, and visually increase the adverse impact of chromatic aberration (CA). Hence the anti-IR filter in front of the imaging chip inside the camera, typically seen as a greenish sheen when the CCD/CMOS chip is exposed to light. The anti-IR filter is combined with an anti-aliasing (AA) filter in a filter pack, which may or may not be easily removable.
One of the basic difficulties you have evaluating a camera for IR (or UV) response is to establish the amount of photographically active IR (or UV) present for the subject under the given shooting conditions, when there is no fixed relationship between visible and invisible light, so your light meter is pretty much useless. While it is true that some cameras, for example the D2H, do meter quite well in IR, you can never rely entirely on this assumption, and it also frequently breaks when you put on a denser IR filter. So, my approach is to compare cameras on a relative basis, using the D70 as a reference point both for UV and IR.
Each generation of Nikon D-series cameras has had its IR sensitivity decreased; or put the other way, the efficiency of the filter pack has increased. Nikon D200 is certainly no exception to this general trend. In fact, it is the least IR-sensitive Nikon DSLR I've ever used. Thus, the D200 has about 4 EV less IR sensitivity than the D70, when I shot IR test scenes with each camera set up identically. This means you are forever tied to using a tripod-mounted camera and additionally, the ISO setting normally needs a healthy lift to keep shutter speeds at a manageable duration. I shot all IR images with Dthe 200 set to 800 or 1600 ISO equivalent.
With the Wratten 89B-type filter I got excessively red images to indicate the red channel of D200 carried the entire IR response. Under sunny skies, the IR response of D200 with 89B was down about 12-14 stops compared to daylight exposure, or some 4 stops down from the D70. This is perfect from the Nikon engineers' point of view, and simply means they have done a good job in order to keep the D200 free of IR-mediated hassles. For a keen IR photographer on the other hand, this poor response, in conjunction with the odd spectral balance, implies you should not count on doing general IR work with the D200. This task is better left to other models such as the D100, D70, or D2H, all of which have 4-5 stops better IR response. Or if you are experimentally inclined, get yourself an old D1 and strip out its internal filter pack to give the camera a tremendous IR sensitivity (no less than + 14 stops compared to D200). Please don't get me wrong, IR photography with D200 is not impossible;, it is impractical since much better alternatives exist. See also the next paragraph.
Another feature with the IR rendition of the D200 is the rapidly declining response to the denser, Wratten 87 or 87C, filters. With the D2H or D70, there is just a small penalty in terms of exposure elongation to pay for the nicer IR rendition of the virtually black 87C filter. With the D200, as with the D2X, the use of 87C will cost you no less than approx. 16 stops of increased exposure compared to the daylight baseline. Moreover, the images I got from the D200 with 89B, 87, or 87C filtration tended to be slightly unsharp and in some cases having excessive graininess and line noise, again in stark contrast to the nice and etchedly sharp IR images you can lift off the D2H or D70.
Infrared rendition of Peace Lily (Spathihyllum
UV-Nikkor 105 mm f/4.5 @ f/16, 800 ISO equivalency, SB-140 flash with SW-5IR filter
UV-Nikkor 105 mm f/4.5 @ f/5.6, 1600 ISO equivalency, SB-140 flash with SW-5IR filter
The IR image taken with the D70 is much sharper despite the greater resolution of the D200. Also, note the much improved IR sensitivity of D70 compared to the D200, in this case at least 4 stops. An SB-140 flash device outputs a very healthy amount of IR, in fact much more enriched in IR than even found in direct sunlight
|Infrared Landscape - I
The weaker 89B (gel) filter shows that IR response predominantly occurs in the red channel. I've tried to balance the image towards less aggressively red colours. Overall, IR shows very limited potential with this camera
Infrared Landscape - II
D200, UV-Nikkor 105 mm f/4.5 lens, Wratten 87C filter on lens.
120 sec exposure at f/11 @ 1600 ISO equivalency
Note the rather excessive image noise here. This perhaps is OK if you want a "dirty" look, but I for one could well do without this kind of noisiness
You should not do IR with the D200. Simple message, simple remedy: Just don't do it. The camera isn't up to the task. There are so much more satisfying approaches to digital IR than those available with D200. On the other hand, the low sensitivity to IR implies you get less problems with skin tones, which are unduly susceptible to excessive IR. So one man's loss is another man's gain.