On Tue, Jun 14, 2011 at 11:03:41AM -0400, Igor Roshchin wrote: > > Hi All! > > After taking photos at a party, I discovered an interesting effect. > It was indoors, with uneven and not very bright light, so, I used > a flash bounced from the ceiling, which made the light rather uniform. > [ . . . ] > I suspect, that this particular color (dye) fluoresces from the flush, > or something like that.
Quite likely - dyes (or pigments) used to colour plastic items often have significant response to ultra-violet light. Even if they don't fluoresce, the output from a flash can produce quite a bit of UV light, and sensors "see" further into the UV than does the human eye. You could try using a UV filter on either the camera or the flash. This isn't a problem that's new to the digital age, though. I used to have all sorts of problems with one of the race cars in CART. To the human eye one of the colours on the car was a fairly bright orange, but on one particular film (Portra 400, IIRC) it showed up once or twice as more of a blue/purple colour. That was in sunlight. Basically, there can be problems with any colour where the spectral response is strongly peaked at a few wavelengths, rather than being distributed more evenly across the range. Colour photography only records three (or, sometimes, four) different numbers, and then uses these to produce an image. Most of the time this works well enough, because the filters used mimic the response of the human eye (which, after all, does very much the same kin d of thing) fairly closely. But it's easy enough to find examples where two items which appear identical to one sensor will look very diffferent to another sensor (or even to the original sensor under different lighting conditions). -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
