Hi Paul- When you scan large numbers of negatives, and in particular older negatives, you learn to expect subtle differences in the channels, from many different sources, and to make adjustments accordingly. I have heard, but cannot personally confirm, that PS as well as many scanning programs over-emphasize the red channel over the green and blue ones, supposedly to ³better render² (read emphasize) Caucasian skin tones. I seem to remember something like 50 red, 30 green, and 20 blue (don¹t quote me on these exactly! ;^) In my experience, most RGB scans of a B&W source will show greater noise and more emphasized grain in the red and blue channels, so I typically start with an emphasis on the green channel, say 30 red, 45 green, and 25 blue. I find that as a starting point, this will give me less noise and minimal grain, as opposed even to using 100% green. Lastly, don¹t forget that not using the channel mixer in PS does not mean that the channels are not being mixed. It only means that you are controlling the results, rather than accepting the channel mixing that PS or the scanning software is performing. Regards, Bill Morse PhotoProspect 450 Harrison Ave. Suite 221 Boston, MA 02118 (617) 868-7642 on 1/22/04 7:04 PM, Paul D. DeRocco wrote: >> > From: Bill Morse [mailto:willym@...] >> > >> > This is a curious statement. If you look at the individual channels of an >> > RGB scan of a B&W neg or print, you will see subtle but potentially >> > significant variations in tonality. > > If there are significant differences in tonality among the three channels, > then the image of the negative won't look monochromatic--you'll see actual > colors in it. I've never scanned a B&W negative, but I've certainly looked > at plenty, and I've never seen any sort of color cast in them. > >> > In addition, as Austin has said, one >> > channel often will be more or less fuzzy, or the grain detail may >> > be more or less pronounced. > > My point was that that's probably the sort of thing that a good engineer > designing a scanner would have figured out, and handled automatically when > scanning B&W negs. But I could be crediting engineers with too much > intelligence. > >> > Finally, if there are any defects in the original >> > (staining, scratches, etc.), they will often be more or less pronounced in >> > the different channels. > > That's a good point. > >> > One question- what leads you to say that using the channel mixer can >> > ³increase the noise² of the image? > > Only if different channels have different amount of noise, and you emphasize > or fail to de-emphasize the noisier channels. For instance, if the green > channel is quieter than the other two, and you select 33,33,33 instead of > 0,100,0, you've got more noise than necessary. > > -- > > Ciao, Paul D. DeRocco > Paul mailto:pderocco@... > >> > >> > Regards >> > >> > >> > Bill Morse >> > PhotoProspect >> > 450 Harrison Ave. Suite 221 >> > Boston, MA 02118 >> > (617) 868-7642 >> > >> > >> > >> > >> > >> > [Non-text portions of this message have been removed] >> > >> > >> > >> > Please visit the Group Homepage to check the Files, and other >> > resources as they are often being updated. >> > >> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint >> > >> > If you wish to receive no emails or just a daily digest, or you >> > wish to unsubscribe, please edit your Membership preferences by >> > visiting this same page. >> > >> > Please follow these basic guidelines: >> > - As threads develop, trim off excess portions of earlier >> > messages to keep them short. >> > - Good manners are required at all time. 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Message
Re: [Digital BW] Scanning b&w negatives
2004-01-23 by Bill Morse