#3ds ratio
Gary,
Well, heck, nobody asked me…! And by the time I'm finished,
you'll remember why. I think the confusion originates because of the
differences between screen ratio, file ratio & film ratio.
Work on an image in the same screen proportions as the film ratio. 35mm is
a 1.5:1 ratio (or 3:2) & 4×5 film is 5:4. A .TGA image of 512×482 on a
monitor is 4:3 (hey, nobody said we're always using square pixels).
Output to 35mm film would be 512×342 pixels, or a multiple (1024×684 or
2048×1368). For 4×5 film, use 512×384 (or 1024×768 or 2048×1536). I hope
this explains the common use of 2048×1536 by service bureaus.
You can also FIT (leave unexposed areas surrounding left & right sides) or
CROP (leave off some information on the top and bottom of your image) for
other formats. In traditional photography, to print a 35mm negative onto
8×10 paper, you either crop off some of the negative, or print the entire
negative onto the paper, leaving some of the paper surrounding the negative
unexposed.
We could also go into film density (2k resolution on 35mm is 2048 pixels
per row measuring 1.5 inches, equal to 1366 pixels per inch, on 4×5 it's
2048 pixels over 5 inches, thus a pixel density of 410 per inch). A pixel
on 4×5 film is roughly 3.3 times larger than the same resolution on 35mm
film. The image begins to look "blocky". To get the equivalent of 2K 35mm
quality on a 4×5, you need an 8K file, for 8×10 you'd need 16K to maintain
a high level of pixel density. So I hope the Yost Group's lab has a Forte.
May I recommend the book I "stole" all this from: Basic Digital
Photography by Norman Breslow (a CSA customer, of course) from Focal Press,
available in many technical book stores. Published by
Butterworth-Heinemann, 80 Montvale Ave., Stoneham, MA 02180.
Kevin Krell – Computer Support Associates