Archived posting to the Leica Users Group, 2003/10/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Jim Hmmm? 4096 shades of gray! Has anyone heard of "Forty Shades Of Green"? Jerry Jim Zietz wrote: > A scanner, like the Nikon 8000 or Minolta 5400, typically scans at a minimum > of 12-bits, or two to the twelfth power which is 4096 shades of gray per > color. In an 8-bit space you only have 256 (two to the eighth power) shades > of gray, which is enough to fool the eye and brain into believing that it is > seeing an even transition from black to white. An RGB color image is made up > of three grayscale channels. > > If you start doing extensive editing, you start dropping out a bunch of > those 256 shades of gray and you get banding or posterization. Other digital > artifacts also come into play. > > So it is best to do the bulk of your editing in the scanning software, and > get the best 8 bits of information into Photoshop's 8-bit space. Lasersoft > SilverFast is a good scanning program because of the control you get and the > feedback with the histogram. The newer NikonScan plug-in works well for me > too. > > The alternative is to scan straight into the 16-bit space, taking every bit > of information the scanner can perceive. This is why most controls are > grayed out in Silverfast when it is set to either 16-bit grayscale or 48-bit > RGB. Then, editing in 16-bit doesn't cause nearly as much degradation as > can happen in the 8-bit space. Once the image is edited, you can either save > it as is or convert to 8-bit and save. A 16-bit file is twice as large as an > 8-bit file. It's all math. > > Photoshop CS will have many more features available in 16-bit mode than are > currently available in Photoshop 7. Some people only work in 16-bit. > -- > jz > > >> <Snip> > >> If you are scanning into Photoshop's 16-bit space, no adjustments need be > >> made in the scanning process. > >> > >> <Snip> > > > > Jim Z could you explain this? > > -- > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html