scan rez / working rez / printing rez...?

  • Thread starter Thread starter Ivan
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Ivan

I've been reading the "Scan Tips" site. It's extremely useful. I'm
understanding curves and histograms now. But I'm wondering about working
resolution and printing resolutions.
I've been scanning negs with my the Nikon V for a week now, and the prints
are very good and promising. But I'm confused about the resolution that I
should be sending my printer__Epson Stylus 875DC. The print set up on this
printer has options for 720dpi and 1440 dpi. If I choose the higher dpi
printing settings should I be sending it identical dpi files? If I send it
a 300dpi file will it re-sample it to 1440? Will I do better to resample to
1440 in PS before I print?
Ivan
 
Ivan said:
I've been reading the "Scan Tips" site. It's extremely useful. I'm
understanding curves and histograms now. But I'm wondering about working
resolution and printing resolutions.
I've been scanning negs with my the Nikon V for a week now, and the prints
are very good and promising. But I'm confused about the resolution that I
should be sending my printer__Epson Stylus 875DC. The print set up on this
printer has options for 720dpi and 1440 dpi. If I choose the higher dpi
printing settings should I be sending it identical dpi files? If I send it
a 300dpi file will it re-sample it to 1440? Will I do better to resample to
1440 in PS before I print?
Click to expand...

Depending on the printer driver settings (paper and ink combination),
the driver will almost certainly resample internally to 720 ppi,
regardless of the ppi your file may be tagged with. The *only* thing
that matters is the number of pixels that will be spread over the
output size. The 1440 refers to the positioning accuracy of the ink
drops after dithering (those are Dots/Drops per inch, which has little
to do with Pixels per inch).

If you e.g. have 3000 pixels in one image dimension and need to cover
10 inches of output, that would result in printed resolution of 300
pixels per inch. The printer driver will then internally have to
resample to 720 ppi, using an unknown resampling algorithm, thus
creating 2.4 pixels out of each pixel that was input. The
interpolation will reduce sharpness/resolution of the output.

If you would have offered enough pixels to avoid further interpolation
(10 inches x 720 ppi = 7200 pixels), the sharpening you would have
applied to that image detail would not be compromised by further
interpolation by the printer driver.

Therefore, you are likely to get the best results by resampling the
image to enough pixels, equal to 720 pixels per output inch, and
sharpen that before sending it to the printer. That will usually mean
that you need to scan at full scanner resolution in order to allow
enlargements with minimal interpolation when postprocessing the scan.

Bart
 
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