Viewfinder
Depending upon how one uses the the S3 UVIR, the viewfinder really doesn't matter – with either UV or IR filters on the lens, there's nothing to see through it. Still, it's the same viewfinder that's in the S3. It's small, compared to more recent mid-range DSLRs, and the diopter bumps out of adjustment easily.
LCD Screen
The S3 UVIR's color LCD screen handles image playback well. It shows good highlight and shadow detail, without looking too flat. The UV and IR images shot are essentially monochrome, and images shot without a filter are just strange. On the S3, the LCD shows very good color reproduction.
The two monochrome LCDs are contrasty and easy to read. The back monochrome LCD shows the S3's full range of shooting options – dynamic range modes, which are useful in UV and IR, and film emulation, which really isn't.
Flash
The S3 UVIR's popup flash produces ultraviolet and infrared light but without any exposure control. The through-the-lens (TTL) exposure system is only sensitive to visible light, so, with either cutoff filter on the camera, the flash goes off at maximum power with every shot.
We found it easier to use the S3 UVIR with an external flash. We used both a Nikon SB80 and studio flash equipment. The SB80's dedicated features show up, but they aren't any more useful than the pop-up flash because they rely on TTL metering. It's easy to set up the SB80 for manual exposure, which allows the user to set exposure in 1/3-EV increments over 7 EV. The SB80 is pretty powerful in infrared, so we were able to shoot out to about 20 feet with it at f/5.6.
Studio flash was a little trickier. The better flash heads have cutoff filters over the flash tubes. Fortunately, one of our old heads blasts both UV and IR like crazy.
We began our testing with the IR filter over the camera lens and of course, couldn't see a thing through the viewfinder. By filtering the flash head and shooting in low light, we got the same effect. We had heard that unexposed, processed transparency film is a quick 
and dirty infrared filter. We had the tails of a few rolls of 120 Ektachrome we shot a while back, and taped some over the business end of the SB80. It worked like a charm. The flash was barely visible at 3 feet but allowed an exposure of f/16 at full power.
Lens
Fujifilm doesn't supply the S3 UVIR with a lens but sent us a Tamron wide-to-tele zoom to use with the test body. We opted for a 60mm f/2.8 Macro Nikkor for much our testing, on the assumption that it might be a popular lens in the scientific/forensic market. We also tried a few other Nikkors – AF versions of the 50mm f/1.8, 35mm f/2, 85mm f/1.8, 20-35mm f/2.8 and the 300mm f/4. All of them work. Our tests weren't controlled enough to note any significant variation in how well they transmit UV or IR. We used them with the Wratten 87c filter and UV filter that Fujifilm provided, a gelatin 87c we had on hand, and with flash filtered through processed Ektachrome.
