Archived posting to the Leica Users Group, 2003/10/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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