Re: Archival Scanning
- From: Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 2 Sep 2008 16:28:44 +0100
In article <dAAqk.43624$yn5.17530@xxxxxxxxxxxx>, Phil Ardussi <nospamplease@xxxxxxx> writes
OK, here goes:The only suggestion I would make would be to reconsider the resolution for your negatives, depending on how particular you want to be and the equipment available to you. Negatives will contain more intrinsic information than any of the other image sources available and it is a reasonable assumption that the scanner itself will limit just how much of that information you can capture. Also, remember that the scanner's quoted resolution is just its sample density, the smallest step between image pixels, and it may not be able to optically resolve 1/2400th of an inch, possible as little as half of that in practice, depending on the scanner.
I do scanning of photos and color negatives for our local historical
society. They have a good deal of material that needs to be scanned into
digital format for preservation purposes.
My scanner is an Epson V500 and gives me lots of options. I consider the
most important settings to be the file format (.jpg, tif, etc.), dpi, and
final size of image. I have heard that 300 dpi is the desired output but the
varying sizes mean that for negatives, the setting should be 2400 dpi, for
4x6's it should be 600 dpi, and 8x10's it should be 300 dpi.
Looking at that, am I on the right track in my thinking?
Outputting at 300ppi (note these are pixels per inch, not dots per inch) will only permit an 8x enlargement of a true 2400ppi scan, which is an 8x12" print from a full 35mm image, or smaller from a cropped area. With less optical resolution you could find your largest practical sharp print size from your archived scan is as small as 6x4".
So I advise you just scan at the native scan resolution (ie. the highest non-interpolated resolution available) for your scanner. Storage is cheap and you don't want to have to do this again, even if you get the chance to.
What is the
suggested file format for archiving? What should be the image size/dpi
setting?
Recommended file format it "tif" because it is an open format that supports lossless compression. Image size and dpi settings are irrelevant since these can be overridden at print time. The dpi setting is simply a single number embedded in the stored file and some software reads it as a recommended or initial setting for output. Most software just ignores it and all software can override it. The image size is then just the number of total pixels horizontally and vertically multiplied by the "dpi" figure. What does matter is the total number of pixels in the image, but if you scan at the recommended resolutions that should be as good as you can get it.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
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