All You Ever Wanted to Know About Digital UV and IR Photography, But Could Not Afford to Ask


8. Light Sources

Infrared (IR) :
Sunlight and electronic flash are typical sources for IR light. Incandescent lamps output IR as well, but the heat produced may be troublesome so for indoors work, flash is strongly recommended. If metal objects are brought to a sizzling heat, over some 400 C, they give off IR in the photo-active spectral range. Before you rush out to snatch your mother-in-law's hot iron for stunning IR shots, notice that the emitted light levels are not very great and I doubt you are able to make this kind of 'heated' imaging with the current line of digital cameras. I'd love to be proven wrong, though.

It is a matter of taste whether you should cover your flash with IR-filters. for example using sheets of Wratten 89B or 87 gel. Normally this isn't necessary when adequate filtration is placed over the taking lens. Still, it would do no harm to filter the flash so as to allow it to emit only IR rays.

Beware of shooting digital IR, or film-based IR for that matter, under heavily overcast or cloudy conditions. There will be relatively low amounts of IR reflected off the ground so it turns quite dark, while the sky will be much brighter. The end result is an image with little foreground detail contrasting a washed-out sky. If you feel this is your preferred shooting style by all means forge ahead and shoot, other people can take the opportunity to catch up with image processing on their clogged hard-drives or similar chores.

 

Ultra-violet (UV) light sources:
Sunlight is an excellent source for UV rays and for film-based UV photography would be the optimal illumination. However, since digital cameras are sensitive to IR and sunlight graces us with plenty of IR, you have to rethink your options.

Artificial light sources for UV comprise mercury vapour lamps, xenon tubes, fluorescent tubes, blacklight (BL) and some halogen bulbs. Electronic flash units may give off a good deal of UV, in particular if the flash tube lacks a UV-screening coating. All UV-sources with continous output can be hazardous to your eyes, so take the necessary precautions and never stare into the light. Special UV-protective googles may be needed, too. The short duration of the flash mitigates some of these issues, but it is never prudent to put any flash up close to people.

 

Making Your Own UV/IR Flash?
Nikon regrettably has discontinued the SB-140, its special flash unit for UV and IR photography. I own one of them so can survive its obsolescence, but a spare unit would come in handy nevertheless.

There still is hope for those lusting for these handy gadgets, however. The secret tip is getting an SB-14 flash together with its SD-7 battery pack. These units were quite popular in the 1980's in era of Nikon F3, and are not difficult to locate today on the second-hand market. Nikon continues to supply spare parts for its products years after they have ceased production and it still is possible to buy the UV adapter SW-5UV and the corresponding IR adapter SW-5IR made for SB-140. Upon closer inspection it turns out the SB-14 and SB-140 flashes are identical in their external appearance. Thus, the UV and IR adapters for SB-140 will fit perfectly on an SB-14, as depicted below.

Which flash is the real thing? Add a spare SW-5UV adapter to an SB-14 and you have the poor man's substitute for an SB-140 (which, by the way, is the flash to the left). Both use the SU-2 module to regulate light output, and may use the more advanced unit SU-3 (middle) as well. SB-14 also has a healthy IR output similar to that of SB-140.

The flash tube on SB-140 is uncoated to allow maximum output in the UV range, whilst that of SB-14 has a yellowish sheen on it indicating it filters away some UV. I have added an SB-14 with SW5-UV to my equipment collection and it works just fine for digital UV work. Hardly surprising, its UV output is less than the "real thing", the SB-140. Test shooting indicates it gives ~ 1 stop less UV exposure than SB-140 with a U-360 filter over my UV-Nikkor 105 mm lens. With the FF + CC20C combination, the difference as expected was less, slightly above 1/2 stop in favour of the SB-140.

The Modified SB-14 works for UV !


Campanula glomerata
D1H, UV-Nikkor 105 mm with
U-360 filter @800 ISO, f/9
SB-140 + SW5-UV
Campanula glomerata
D1H, UV-Nikkor 105 mm with
U-360 filter @800 ISO, f/5.6
SB-14 + SW5-UV
All You Ever Wanted to Know about Digital UV and IR Photography, But Could Not Afford to Ask

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Last update 25 December, 2004