Help talk:Scanning

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Contents 1 First comments 2 Resolution 3 Formats - DjVU 4 PNG vs. JPG 5 Category:Scans 6 Warning at 5?

[edit] First comments

A very good start. Some additional points:

• I usually scan to PNG or TIFF, and if that becomes too large, I convert to JPG afterwards. PNGs can also often be (losslessly) shrunk quite a bit using optipng.
• Use the "remove moiré" function of the scanner, if it has one.
• I've seen (elsewhere) the advice that scanning at an angle may reduce scanning artefacts. Never tried it myself, though.
• The black sheet as a background must be mentioned. I should've thought that trick was so old and well-known (I've used it long ago, when all we had were Xerox copiers...) that it was not necessary to mention it, but the Darwin DR proved me wrong on that one.
• Maybe add a few external links such as scantips or halftone scanning and others?

I'm sure this page will evolve into a truly useful guide. Lupo 15:02, 4 March 2008 (UTC)

I've added all but the second and third in - the second because I don't think it's a particularly common software feature (and, in any case, software varies so much that it's hard to say much about what they might or might not have in their scanning software); And the third because rotating the image after scanning at an angle might well produce as many problems as it avoids.

I still have to see a scanner that doesn't have a "remove moiré", "descreen" or similar function. Maybe that just speaks of my limited experience. :-) Lupo 09:39, 5 March 2008 (UTC)

P.S.: See [1] or [2]... both state that most scanner software includes such a feature. Lupo 09:51, 5 March 2008 (UTC)

Oh, descreen. Sorry, I don't actually do much work with half-toned images, and that's what those functions are mainly for, so I largely can ignore them =). Adam Cuerden 12:07, 5 March 2008 (UTC)

[edit] Resolution

This is an awesome start. I look forward to seeing this expand.

About resolution. Can you say if beyond a certain point it's a waste of time and pixels? My scanner scans up to 1200dpi, but the files are so large that my image editing software struggles to cope (eg with cropping or rotating). Even with 600dpi it struggles. (This was using Irfan Image Viewer.) So I gave up and went 400dpi and it was still plenty huge of course. I just wonder how much difference there is going from 400 to 600 to 1200. pfctdayelise (说什么?) 05:57, 5 March 2008 (UTC)

It's occasionally useful for very small, and/or very detailed works of art. I think that Image:William Hogarth - Gin Lane.jpg was at around 600 dpi or so. But those resolutions are, in fact, largely intended for the scanning of film, slides, and microfilm. Adam Cuerden 11:47, 5 March 2008 (UTC)

[edit] Formats - DjVU

Does anyone have any experience with creating DjVU files from scans? I have a feeling it is recommended for pages dominated by text, although one site said it could be used for line drawings as well. Recommendations? pfctdayelise (说什么?) 06:02, 5 March 2008 (UTC)

I don't think that most scanner software supports it anyway. If your scanner does, I'd try experimenting with it yourself. Adam Cuerden 06:34, 5 March 2008 (UTC)

[edit] PNG vs. JPG

In this section of the article, it says:

"In any case, it's usually best to scan to a lossless format, such as PNG, TIFF, or, if you have to, BMP first, as you lose quality going from JPG to PNG, but not the other way around."

Wait a minute... surely that should say:

...you lose quality going from PNG to JPG, but not the other way around.

Right? - dcljr 06:00, 18 March 2008 (UTC)

I think I phrasesd that oddly - what I meant was that JPG has already lost quality that won't be regained by a switch to PNG, but a JPG made from a PNG is the same or better as a JPG made in the first place. Adam Cuerden 06:20, 18 March 2008 (UTC)

[edit] Category:Scans

is now available. Should we mention that in the text? --11:50, 10 October 2008 (UTC)

[edit] Warning at 5?

I don't think we warn about uploads in excessive of 5MB anymore, do we, as the text claims here? Dcoetzee (talk) 22:42, 13 March 2009 (UTC)