24 Apr
2015
24 Apr
'15
6:48 a.m.
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).
Al, I hope that's acceptable for BitSavers - I have a number of things that
are missing, and I was planning on scanning them in, and sending them along.
Noel
24 Apr
24 Apr
7:07 a.m.
On Apr 24, 2015, at 9:48 AM, Noel Chiappa <jnc at
mercury.lcs.mit.edu> wrote:
If you?re looking to scan for human consumption, bitmap works ok. But I?ve found that OCR
programs seem to want grayscale. Why that is, I don?t know; they do seem to convert it
to bitmap at some point. Possibly the threshold logic is more complex.
That brings up thresholds. When scanning, or converting to, bitmap, you have to set the
gray threshold that is the cutoff between white and black. The default would typically be
128 (50%). Depending on the scanner and the condition of the originals, that threshold
may be fine, or it may be far off the optimal. A good approach is to scan a number of
representative pages in grayscale, and experiment with different threshold settings to see
which one is the best. Basically, you?re looking for the compromise between filled in
loops, and broken thin lines. For printed originals, this is probably not all that
critical; for typewritten material, it is far more so.
paul
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). 
7:59 a.m.
On 2015-04-24 16:07, Paul Koning wrote:
Speaking of which, anyone have a good suggestion for OCR nowadays? I
would really like to throw all the current PDF scans of manuals that
sits out there at OCR, to get the documents back to sane sizes, and also
make it possible to update the documents over time when needed...
Johnny
On Apr 24, 2015, at 9:48 AM, Noel Chiappa <jnc
at mercury.lcs.mit.edu> wrote:
If you?re looking to scan for human consumption, bitmap works ok. But I?ve found that
OCR programs seem to want grayscale. Why that is, I don?t know; they do seem to convert
it to bitmap at some point. Possibly the threshold logic is more complex.
That brings up thresholds. When scanning, or converting to, bitmap, you have to set the
gray threshold that is the cutoff between white and black. The default would typically be
128 (50%). Depending on the scanner and the condition of the originals, that threshold
may be fine, or it may be far off the optimal. A good approach is to scan a number of
representative pages in grayscale, and experiment with different threshold settings to see
which one is the best. Basically, you?re looking for the compromise between filled in
loops, and broken thin lines. For printed originals, this is probably not all that
critical; for typewritten material, it is far more so. 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).
8:09 a.m.
On Apr 24, 2015, at 10:59 AM, Johnny Billquist <bqt
at update.uu.se> wrote:
...
Speaking of which, anyone have a good suggestion for OCR nowadays? I would really like to
throw all the current PDF scans of manuals that sits out there at OCR, to get the
documents back to sane sizes, and also make it possible to update the documents over time
when needed?
Acrobat had (has?) an OCR feature which I?ve used at times. It?s amazingly primitive and
works to a ?just barely acceptable? level.
I once found an open source OCR program, tried it, concluded it wasn?t worth the trouble
of downloading it and forgot the name.
At this point, I use Abbyy FineReader, which is a commercial product (not really cheap,
but not outrageously expensive either). Windows based, unfortunately. Among other
things, it has a ?training? mode where you can teach it what the letters in your source
material look like. If you?re dealing with stuff that?s at all marginal ? like line
printer listings or typewriter material, never mind dot matrix ? spending an hour or two
in training mode makes an incredible difference. I?ve been using this OCR to read CDC
6600 wire lists, which are a challenge (low quality typewriter text). I also tried it the
other day on old lineprinter listings of the THE operating system; those were too far gone
to be useable, partly because they are upper case only printouts with . overprinting on
letters that are upper case in the original mixed case source files. Getting OCR to tell
an O from an O with . overprint, reliably, just wasn?t doable.
So OCR will work within reason, but there is still material that can only be handled by
human eyes.
paul
7:40 a.m.
On 4/24/2015 8:48 AM, Noel Chiappa wrote:
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.
- J.
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). 
7:42 a.m.
I always scan to optimize OCR, that way the document will be found online
via a search engine.
Lee C.
On Fri, Apr 24, 2015 at 7:40 AM, js at cimmeri.com <js at cimmeri.com> wrote:
On 4/24/2015 8:48 AM, Noel Chiappa wrote:
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.
- J.
--
Lee Courtney
+1-650-704-3934 cell
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).
7:46 a.m.
On Apr 24, 2015, at 10:40 AM, js at cimmeri.com
wrote:
On 4/24/2015 8:48 AM, Noel Chiappa wrote:
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.
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.
paul
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).
8 a.m.
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.
- J.
On Apr 24,
2015, at 10:40 AM, js at cimmeri.com wrote:
On 4/24/2015 8:48 AM, Noel Chiappa wrote:
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.
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).
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.
8:13 a.m.
On 4/24/2015 10:03 AM, Johnny Billquist
wrote:
On 2015-04-24 17:00, js at cimmeri.com
wrote:
Again, TRY it. Unless you need to
magnify things 10-20x the original,
100-200 is more than sufficient *in
practice* for most purposes.
Despite the differences in opinion on
*perceived* DPI, the actual thrust of my
argument here is that it's far more
important to preserve the _grayscale_
quality of a document -- especially for
those that have photos pictures,
diagrams -- than any excessive DPI.
- J.
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:
> > 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.
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. 
8:23 a.m.
>>> 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.
>> I would not call 90 dpi ?good enough?. [...]
> Why don't you actually try it.
I have tried it (I have a scanner capable of resolutions up to 300dpi)
and I agree: 90 dpi may be "good enough" for good-quality printing in
good shape with a large font and humans reading it. If the printing is
dodgy, if the original isn't in the best of shape (dirty, creased,
etc), if the print is small, if it's something other than humans trying
to read it - each of those is reason to want better resolution.
Storage is cheap. Especially, storage is _very_ cheap compared to
discovering after the fact that you don't have as good a scan as you
turn out to want of a document that's pretty; much unobtainable.
300dpi versus 90dpi is a factor of only a little over 11 in file size.
If that bothers you, send me the high-res scans and I'll keep them
safe; I'm willing to spring for a terabyte or two of disk if necessary
for the sake of keeping such things around.
> Also, I'm assuming reading on a screen (where
I read most of my
> vintage manuals) vs. re-printing.
That's fine for your use, perhaps. Not everyone does that.
> 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.
I can tell the difference between a two-pixel-thick line and a
three-pixel-thick line on a 300dpi printer. Or, let me be precise, I
could the last time I tried; admittedly, that was a while ago, but I've
not had reason to think my visual acuity has got any worse since then.
/~\ The ASCII Mouse
\ / Ribbon Campaign
X Against HTML mouse at rodents-montreal.org
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
8:03 a.m.
On Apr 24, 2015, at 11:00 AM, 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.
You?re assuming I haven?t. In fact I have done scans for a long time, with different
resolutions; my comment was not based on ignorance. Ditto my statement about professional
printing practice. And while a lot of computers have 90 dpi screens, some (like mine)
are substantially better. Finally, depending on your eyes you might well be reading at
greater than 1:1 scale.
paul
...
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. 
25 Apr
25 Apr
12:45 a.m.
Am 24.04.15 um 17:00 schrieb js at cimmeri.com:
My screen resolution is 90dpi. Anything over that is
pure waste.
A 90 dpi screen is no longer acceptable to me. I type this on a
15"
hi-dpi screen ("Retina Display" ...) with 220 dpi. This is barely enough
to no longer see pixels and get sharp font characters. If I have to use
a 90 dpi to 110 dpi screen I always need to scale up PDFs to about twice
the original size to make them readable. The measure is pixels per
character and at 90 dpi this is _way_ to low to be well readable at 1:1.
Text is scanned at 600 dpi b/w best. Makes it easy to read an reprint on
laser printers. There is still the option to scan individual pages in
greyscale, if there are drawings etc..
--
tsch??,
Jochen
3528
days inactive
3529
days old
12 comments
7 participants
participants (7)
-
bqt＠update.uu.se -
jkunz＠unixag-kl.fh-kl.de -
jnc＠mercury.lcs.mit.edu -
js＠cimmeri.com -
leec2124＠gmail.com -
mouse＠Rodents-Montreal.ORG -
paulkoning＠comcast.net