Resolution?

  • Thread starter Thread starter Hecate
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Hecate

I'm going to be purchasing a flatbed. It's main use will be twofold -
OCR and image scanning.

What I#'d like people to comment on is this:

Given that the image scanning will most likely only be prints ( I
already have a Minolta 5400) what input resolution do I need to look
at?

I should explain that these are for old images, provided by clients,
for restoration where it is unlikely they have a negative.

I'm really looking for a minimum requirement rather than a specific
scanner, though I have looked at scanner with anything from 1200x2400
to the Epson 4870. Any recommendations will be welcomed though.

Thanks.
 
I'm going to be purchasing a flatbed. It's main use will be twofold -
OCR and image scanning.

What I#'d like people to comment on is this:

Given that the image scanning will most likely only be prints ( I
already have a Minolta 5400) what input resolution do I need to look
at?

I should explain that these are for old images, provided by clients,
for restoration where it is unlikely they have a negative.

I'm really looking for a minimum requirement rather than a specific
scanner, though I have looked at scanner with anything from 1200x2400
to the Epson 4870. Any recommendations will be welcomed though.
Click to expand...


For OCR, you will routinely want 300 dpi. However, for very tiny fonts,
more can be useful to enlarge the tiny fonts, like 400 dpi.

You might scan text documents at 600 dpi line art mode for best
reproduction at original size.

The general idea is that the ratio of (scanning res / printing res) is
the enlargement factor. Scan at 600 dpi, print at 300 dpi, gives
double size copy.

So for photo prints, probably 600 dpi could be a reasonable limit (just
assuming you will print at 300 dpi, and will probably enlarge prints no
more than double size). You can of course use a 1200 dpi scanner at 300
or 600 dpi.

It is the same idea for film, so we need the largest numbers to enlarge
film (because film is small, and we enlarge it a lot). But prints dont
really enlarge so well at much more than 2x. We use film for that.
 
Photo print paper has a maximum resolution of about 5-7 lp/mm, which
translates to about 250 to 350 dpi. But that's best case, with reasonably
modern glossy paper, and a print that is in superb condition. I find I
rarely get any scanning improvement beyond about 300 dpi. For line art made
with a good printer I have gone to 600 dpi on occasion. Also, occasionally
I have gone to higher dpi to avoid moire due to matte print textures,
halftone, etc.

But you won't find any scanner that can't do that and more, so resolution
probably isn't an issue.

Don
 
For OCR, you will routinely want 300 dpi. However, for very tiny fonts,
more can be useful to enlarge the tiny fonts, like 400 dpi.

You might scan text documents at 600 dpi line art mode for best
reproduction at original size.

The general idea is that the ratio of (scanning res / printing res) is
the enlargement factor. Scan at 600 dpi, print at 300 dpi, gives
double size copy.

So for photo prints, probably 600 dpi could be a reasonable limit (just
assuming you will print at 300 dpi, and will probably enlarge prints no
more than double size). You can of course use a 1200 dpi scanner at 300
or 600 dpi.

It is the same idea for film, so we need the largest numbers to enlarge
film (because film is small, and we enlarge it a lot). But prints dont
really enlarge so well at much more than 2x. We use film for that.
Click to expand...

Thanks Wayne, I was hoping you might answer. I had been using an Agfa
Snapscan E50, but it's getting old and cranky so I was looking for
something new. That had a 600x1200 scan but I wasn't sure whether that
was enough - give me some film and I wouldn't have a problem, but
scanning old prints and I was rather less sure. <g>

You just saved me a lot of money. Thanks!
 
Photo print paper has a maximum resolution of about 5-7 lp/mm, which
translates to about 250 to 350 dpi. But that's best case, with reasonably
modern glossy paper, and a print that is in superb condition. I find I
rarely get any scanning improvement beyond about 300 dpi. For line art made
with a good printer I have gone to 600 dpi on occasion. Also, occasionally
I have gone to higher dpi to avoid moire due to matte print textures,
halftone, etc.

But you won't find any scanner that can't do that and more, so resolution
probably isn't an issue.
Click to expand...
Thanks Don. I don't have any problems with film, but I wasn't so sure
of my ground with prints. None of the prints I'm likely to be working
on are anything near "superb" so I'll go for a good, but cheaper
scanner rather than the obvious overkill of a 4780. I can always buy
one later if I need to scan MF film. So you and Wayne have saved me a
fair amount of money. Appreciate your help.

Thanks,
 
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