10th October 2004, 03:35 PM
10th October 2004, 10:47 PM
Originally Posted by Adzz
3) Yes, but quality not acceptable to me.
22nd October 2004, 12:28 PM
The differences in quality between scanning 300dpi & 600dpi is only obvious if you enlarge your 3R photo. If you simply scan to print 3R from the 3R you have, The resulting 3R will not be different if scanned in 180dpi or 1200dpi. Normally, prints look good if printed in 150dpi to 300dpi. So to play safe, you can scan at 300dpi if the largest you'll re-print is 4R. If not, depending on what size you want to print, say S8R and your source is 3R, by taking the factor 2.4 (12" is 2.4 x 5"), to print S8R at 150dpi to 300dpi, you'll need to scan your 3R at between 360dpi to 720dpi. So 600dpi is good (250dpi).
Also, professional shop may produce better quality scans because they tweak the scan (not always to the better). That's why scanning it yourself is more flexible and up to you to tweak it.
22nd October 2004, 01:24 PM
I based my answer below on Nyquist theorem which applies for sampling continuous time signals. The concept seems applicable for scans as well.
Prints are roughly 300dpi in terms of resolution. To digitise it (i.e. scan) for reproduction at original quality, you need to double the "resolution" (Nyquist frequency), i.e. 600dpi. So scanning at 600dpi will enable you to reproduce the original 3R with little loss of details. Scanning higher than 600dpi doesn't get more details because the source only has 300dpi of information.
However, the above has assumption of "perfect" digitisation process. To cater for some deficiency in the equipment, you may want to scan at slightly higher resolution, e.g. 800dpi.
You'll be able to produce larger prints (than 3R) with some loss in details. Whether the loss in quality is acceptable or not depends on the viewer.
(negatives are different and contain significantly higher resolution than 300dpi, so scanning at >3000DPI is able to extract more info)
Last edited by mpenza; 22nd October 2004 at 01:29 PM.