24 Apr
2015
24 Apr
'15
8:03 a.m.
On 2015-04-24 17:00, js at cimmeri.com wrote:
On 4/24/2015 9:46 AM, Paul Koning wrote:
Why don't you actually try it. Also, I'm assuming reading on a screen
(where I read most of my vintage manuals) vs. re-printing. My screen
resolution is 90dpi. Anything over that is pure waste. Maybe you have
better eyes than I do, but I can't discern image quality over 100-200dpi
for printing.
That seems like a weak argument. While looking at documents on a screen,
I often magnify them to see details. So a higher resolution of the
source material than what the screen offers is very meaningful.
Johnny
On Apr
24, 2015, at 10:40 AM, js at cimmeri.com wrote:
On 4/24/2015 8:48 AM, Noel Chiappa wrote:
I would not call 90 dpi ?good
enough?. The professional printing rule
of thumb is that for an n grayscale dots per inch halftone image you
need 2n DPI resolution. So 90 dpi is, at best, low grade newspaper
resolution. A standard commercial grade scan for good quality
printing is 260 dpi or so ? which means 300 is certainly a fine
choice. 150 or below may well be acceptable if that?s the best you
can get, but you?re definitely compromising image quality if you do that. > From: shadoooo
> I'm scanning at 600dpi grayscale, lossless compression.
I've been scanning a few things too, and I found that 600dpi grayscale
produced absolutely enormous files (many, many MB's per page, for
prints), no
matter what I tried to do, compression-wise.
600dpi black and white, followed by saving as TIFF's with CCITT Group 4
compression, produced immensely smaller files (small 100's of KB's
for the
same pages), and they are quite readable (even the fine letter seems
to be
readable - b/6 is quite distinguishable, etc).
While smaller, I've always
found 1 bit b/w scans to be nightmarish to
read (too much font detail is sometimes lost), and forget about
grayscale pictures and diagrams coming across intact. Grayscale is
best. The problem comes in overdoing the DPI. Even 90 dpi is good
enough. 150, more that sufficient. 300 or 600, total waste, but
they are (obviously) the most accurate renderings.