|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
The data that accompanies the target indicates the colors of the piece of film (or at least the average for that batch of IT8 targets), not the colors of the original light used to expose the target film. So you would be correct that any target should suffice for calibrating a scanner, if color were really just a simple combination of three frequencies representing red, green and blue. But light is made up of an infinite number of frequencies covering a particular range, and all RGB devices (including the eye) perceive color by applying three different spectral response curves to the incoming light, one peaking at red, another at green, and another at blue. Film itself has basically three colors of dyes that absorb red, green and blue, but the precise spectral response curves of these dyes don't exactly match the curves of the rod cells in the eye. Nor do they precisely match the curves of the CCD elements in a scanner. Because of this, it's possible for a scanner calibrated with an IT8 target made out of one type of film to produce slightly inaccurate scans when scanning a different type of film. But these are second-order effects. A scanner calibrated with any IT8 target will produce good results on any type of film, just not perfect. As I said earlier, if you want scans to look like the original scene, you'll have to tweak the colors anyway, so it probably doesn't matter, but if you want scans that look exactly like the slide, because you like the color rendition of that type of film, then you should ideally calibrate with a matching target. -- Ciao, Paul D. DeRocco Paul mailto:email@example.com > From: gary > > I really don't follow this logic. > > Is the IT8 image done with a camera, light, and physical target, i.e. you > photograph a standard of some sort? Then it makes sense to me > that you could > need such a target for each variant of film. If the IT8 by itself > represents > a standard for the scanner to scan, then the film shouldn't > matter, i.e. the > manufacturer of the target should compensate for the film. - Turn off HTML mail features. Keep quoted material short. Use accurate subject lines. http://www.leben.com/lists for list instructions.