On Friday, July 25, 2003, at 01:58 pm, Slater King wrote:
If the pencil goes from top corner to top corner, you'd get 3 squares, lying
next to each other - all good and nice. Make the pencil go between
diagonally opposite squares and you'll get the 3 squares again, but this
time like a staircase ... and don't forget that the pencil brushes some
other squares - draw it out and you can see that it's easier to say the
number of squares the pencil is not touching, rather than the number it is
(circa 80%).
Thanks Slater for your long explanation. Can this be kept in its own little space in the Archive to avoid the answer being given again.
Additionally I would point out that the scanned lines will vary depending on the scanner used. I saw a demonstration of a drum scanner a while back. The demonstrator was at pains to point out the way in which the scanner lens could pick up 12,000 lines per inch. This was rarely used of course because 6,000 lpi was more than enough for most purposes. This scanner was able to scan precisely 1/12,000, 1/6,000 or 1/4,000 wide strips or any other number chosen. Cheap scanners might nominally be 4,000lpi but that line could be 1/2,000 inch wide.
I have also seen a digital dupe which output via LVT onto Velvia film. Pixel counting was used so that the scan lines and output lines exactly matched. The original and the dupe were indistinguishable. The file size was very close to 40Mb for a 6x8cm piece of film. Allowing for the fact that litho repro will never manage to pixel match we need a file 1.4 times bigger for press. This is why so many of us standardise on 55Mb files for uses like stock pictures where we don't know what size the repro will be. I use 72Mb for Xpan to enable the image to be cropped and still have good height. A magazine cover sale yesterday was a vertical crop from a horizontal frame.
( I was sent some digital capture files by a friend recently. There was very slight camera shake on some of them which had an odd effect on a car number plate which appeared in all instances sharp. H was also - and ll, F was l and =. )
Bob
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