> From: Robert Logan > > The tools of tomorrow, be they better hardware, > or better software, may allow me to manipulate > the 16 bit data (14 bit in my case), better > to produce a better looking image. > > If I have 256(8bit) greens in my file, and in the > other I have 257(16bit), then I have more to work > with to achieve an end.
I haven't read this entire thread, but in what I've read I haven't heard mention of noise. What limits the number of useful bits is the noise level. A good scanner may well have better than an eight-bit S/N ratio, but I doubt anything out there does better than twelve, except perhaps a high-end drum scanner. Small CCD cameras often provide raw files with more than eight bits, but the extra bits are complete rubbish. The larger CCD cameras have nine bits of useful data, maybe ten under optimum conditions. If you scan a slide (or negative) with some clear blue sky, that's a good test of the noise level of the scanner, since sky is completely textureless, and virtually noise-free. If you blow up the image and examine the pixels, and it looks like blue confetti on your eight-bit display, then you really don't need any more than eight bits, because the noise will take any finer gradations and dither them up into the top eight bits. This is pretty easy to prove in practice, by taking a 16-bit scan, copying it and truncating the copy to eight bits, and then seeing if a strong contrast enhancement curve gives you noticeable banding in the latter but not the former. With enough noise (whether from the CCD or the film grain), the extra bits won't matter. -- Ciao, Paul D. DeRocco Paul mailto:[EMAIL PROTECTED] ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
