[texhax] Illustrations from other books

[William F. Adams]

On Sep 25, 2005, at 1:22 PM, pierre.mackay wrote:
<snip>
> I suggest photography for any half-tone in which you can sense the 
> screening, because direct scanning tends to give you a very precise 
> picture of the screened dots. 300 dots per inch is all you need for 
> half-tones, but if you want really sharp black and white line art, you 
> will have to learn some techniques in GIMP and work from as much as 
> 1200 DPI.

<snip>

It's important to note that these figures are for 100% of output size.

Also, it's often worth going higher if the image has fine details or 
small text.

> Issue 23.1 after page 93 will show (Figures 4 and 6) what the risks of 
> getting too precise a picture of the half-tone screen are.

It's better to de-screen any already screened half-tone if you're using 
greyscale, unless doing a dot-for-dot scan and output is feasible.

Some scanners have decent automatic options for this, or one can do the 
old standard:

  - scan at the original output resolution (this captures all possible 
detail)
  - do a gaussian blur using a number of pixels slightly less than the 
factor of the intended output dpi to the original dpi. (so if one has 
1200 dpi original and is outputting at 100% @ 300dpi, blur using ~3.75 
pixels for a sample)
  - downsample to the output resolution
  - do not sharpen much if at all (you've already captured the 
sharpening applied to the original before output)

Better still is to get a new photo of the original or use a dot-for-dot 
scan --- if you can find the original galleys for a book the latter is 
an excellent option.

William

-- 
William Adams, publishing specialist
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