What is the cause of tears in scans?
Posted: Tue Jan 17, 2017 9:48 am
I have noticed that a large proportion of scans performed by other people have tears in them in the form of dropped rows of pixels. They are not rare.
For example,
https://i.imgur.com/KD2Kgca.jpg
https://i.imgur.com/FXFEyWn.jpg
When an image like that is processed with a descreen filter, the missing row disturbs the pattern, is spread out, and gets very noticeable and ugly. What is the cause of this and why is this issue so common?
If a sound card or a CD ripper dropped samples like so, the system would be considered broken and not be used. I have owned 2 scanners CanoScan 4400F and 5600F, and have never encountered this. I am able to scan a CD at 1200 dpi without the scanner stopping. Anything wider than that and the scanner does have to stop, but it is nevertheless able to restart from the precise position. I sometimes see the problem on 300 dpi scans downloaded from the internet.
Does it depend on the drivers? Or the interface method? If this issue comes up, I would like to be able to advise on how to avoid it.
For example,
https://i.imgur.com/KD2Kgca.jpg
https://i.imgur.com/FXFEyWn.jpg
When an image like that is processed with a descreen filter, the missing row disturbs the pattern, is spread out, and gets very noticeable and ugly. What is the cause of this and why is this issue so common?
If a sound card or a CD ripper dropped samples like so, the system would be considered broken and not be used. I have owned 2 scanners CanoScan 4400F and 5600F, and have never encountered this. I am able to scan a CD at 1200 dpi without the scanner stopping. Anything wider than that and the scanner does have to stop, but it is nevertheless able to restart from the precise position. I sometimes see the problem on 300 dpi scans downloaded from the internet.
Does it depend on the drivers? Or the interface method? If this issue comes up, I would like to be able to advise on how to avoid it.