On Tue, Jun 14, 2011 at 02:46:42PM -0400, Igor Roshchin wrote: > > > Tue Jun 14 13:48:28 EDT 2011 > John Francis wrote: > > > 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. > > John, > > Even though purple might have an mixture of blue/violet with red, > I would expect that purple would be farther on the spectrum and closer to > the violet part than blue. > > That would mean that hitting the violet (or UV) part of the spectrum > should shift the color toward violet, not toward blue.
The sensor doesn't qualify the light hitting it by the actual wavelength. Some UV light excites the sensor at the blue pixels, registering blue, but gets filtered out of the red pixels. your camera can't tell the difference between a monochromatic blue light and a mixture of blue and UV light that excites the blue sensor, but is blocked by the Bayer filter over the red and green pixels. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
