scanning dpi

  • Thread starter Thread starter Charlie Klatzkin
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Charlie Klatzkin

Is there an article I can read about the best dpi for scanning photos and
35mm negatives? I'm looking for the optimal dpi for canning pictures and
negatives without saving multi-MB files. There is a point where too much
dpi is wasted when printing a 4x6 or 5x7 to a local standard photo printer.
 
Charlie Klatzkin said:
Is there an article I can read about the best dpi for scanning photos and
35mm negatives? I'm looking for the optimal dpi for canning pictures and
negatives without saving multi-MB files. There is a point where too much
dpi is wasted when printing a 4x6 or 5x7 to a local standard photo
Click to expand...
printer.

www.scantips.com

If a printer (e.g. Fuji Frontier) uses 300ppi data, then you need to
supply 1200x1800 pixels for a 4x6in, and 1500x2100 pixels for a 5x7in
print. Other pixel sizes will be resized (resampled) by the printer,
which may or may not deteriorate the image quality. If you want to be
sure, just give them what they need.

The quality of those pixels can be increased if you scan more of them
(at least 2x in each dimension), and then down-sample to the required
pixel size. After down-sampling, you should apply some sharpening to
compensate for fine detail contrast losses due to the scanning,
resampling, and printing processes.

So, in your case, if you never intend to print larger than 5x7in, and
you want the better quality, I would scan a file of at least 3000x4500
pixels (it will even allow to print a decent 8x10in). You can then
downsample and crop that file to the pixel size needed for the final
output. Do note that the aspect ratio of 5x7 is more square than 4x6,
so I took the longest dimensions to accomodate both.

Bart
 
Before simply scanning for optimal printer resolution at a specific smaller
scan size you really need to consider what else you might want to do with
the image at a later time.

In reality it is easier to scan the image the first time at a size that is
more optimal for manipulation, retouching and possibly printing at a larger
size then to redo it later when the original negative or transparency might
have been lost or damaged. CD and DVD storage is dirt cheap compared to the
loss of a valued picture.

For 35mm originals for most people a scan of 2000-2400 dpi, yielding a file
size of 20-24mbs, is the most practical. This allows for significant
cropping with enough pixels left over for a quality image, especially if you
print no larger that 5x7. An image of this size will easily scale up to 11
x 14, and actually larger, if ever desired.
 
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