Reply To: InDesign/Prepress Myths

Raphael,

The only reason I'd scan at 1200 dpi would be if I had to enlarge the image considerably (±400%), OR … if I'm going to convert it to a pure black-and-white bitmap [*]. These can be printed at the output resolution — 2400 dpi, if you really really want super quality. 1200 dpi is usually “good enough”. What David said: grayscale and full colour images will be downsampled, for the sole reason there is no point in sending more than 300 dpi to an imagesetter. Even if you force ID to include the full resolution into the PDF, the imagesetter itself will sample only at intervals defined by its halftone interval. (Ignoring any of the RIP oddities David encountered )

The black-and-white 'trick' works because these images do not go through the halftone machinery.

[*] I should probably add that if you see only black-and-white pixels, it's not “by definition” a black-and-white image. It could be anywhere, up to 64 bit RGB plus alpha. Link Info shows what color model it really is.