Re: Dot pattern?
In a CTP environment the best AM/XM dot shape is round. By that I mean a non-transforming dot that is round in the highlights and simply increases in size to represent darker tones. Here are a few reasons why this is the "best" dot shape for CTP compared to Euclidean, Elliptical, Square, etc. dot shapes:
1) Dot shape is the same for all screen angles - eliminates dot gain due to dot shape variables, reduces single channel moiré issues
2) Dot is non directional, i.e. all screen angle dots are equally react the same to directional press issues such as slur and doubling
3) The tone bump that occurs when dots touch occurs in the shadows at 75% so is much less visible in presswork (e.g. vignettes/skin tones) compared to Euclidean (50% bump where dots form a checkerboard) or Elliptical 40% & 60% bump.
Round dot is not normally used in a film workflow because, with linear film, the dots touching in the 3/4 tones results in a loss of shadow detail.
thx, gordo