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From: mcollins on 13 Mar 2006 08:01
I've seen advice on this newsgroup to scan everything bigger than
3-1/2 x 5 at 300 dpi. Now I have several versions of the same school
portrait of a child, one wallet size, one 5 x 7, and one 8 x 10. If I
were to scan only one photo, what dpi setting should I use? Is it
better to scan a big photo or a small photo? (I want to store it on a
CD-R as a jpg at 90 quality)
From: Surfer! on 13 Mar 2006 10:16
In message <bvqa12duhpbpnru7bsadh6qt98pegc2mfr(a)4ax.com>, mcollins
<mcollins(a)nospam.com> writes
>I've seen advice on this newsgroup to scan everything bigger than
>3-1/2 x 5 at 300 dpi. Now I have several versions of the same school
>portrait of a child, one wallet size, one 5 x 7, and one 8 x 10. If I
>were to scan only one photo, what dpi setting should I use? Is it
>better to scan a big photo or a small photo? (I want to store it on a
>CD-R as a jpg at 90 quality)

Which photo to scan depends in part on the quality of the photos - but
if they are all as good (or bad) as each other, I'd scan the large one.
You can use that scan to make small prints, but using a scan of the
small photo to make large prints will come unstuck.

--
Surfer!
Email to: ramwater at uk2 dot net
From: Wayne on 13 Mar 2006 10:35
In article <bvqa12duhpbpnru7bsadh6qt98pegc2mfr(a)4ax.com>,
mcollins(a)nospam.com says...
>
>
>I've seen advice on this newsgroup to scan everything bigger than
>3-1/2 x 5 at 300 dpi. Now I have several versions of the same school
>portrait of a child, one wallet size, one 5 x 7, and one 8 x 10. If I
>were to scan only one photo, what dpi setting should I use? Is it
>better to scan a big photo or a small photo? (I want to store it on a
>CD-R as a jpg at 90 quality)


The correct concept is instead about the requirements to achieve the
desired goal.

Digital images are dimensioned in pixels, and scanning resolution is
specified in dpi (pixels per inch). That means that if you scan a 8x10
inch photo at say 100 dpi, then you will create an image size of
800x1000 pixels. The question is what size image do you want?

If you need a larger image size, you scan with greater resolution.
If you need a smaller image size, then you can either scan at lower
resolution, or later resample the image to be a smaller copy.

Scanning at 300 dpi is a fine rule of thumb for the goal of reprinting a
copy at original size.... scan 4x5" and print 4x5", then 300 dpi is just
right for printing. Or, if you will enlarge a wallet size print to
print a larger copy, then scanning at 600 dpi will allow printing double
size at 300 dpi (however photo prints dont really enlarge all that well
- scanning original film is much better for enlargements).

If your goal for creating the image is to view it on the computer video
screen, then the video screen size (perhaps 1024x768 pixels) is the
correct guide for image size ... an image larger than the video screen
won't serve much purpose on that computer screen.

--
Wayne
http://www.scantips.com "A few scanning tips"

From: rafe b on 13 Mar 2006 11:16

"mcollins" <mcollins(a)nospam.com> wrote in message
news:bvqa12duhpbpnru7bsadh6qt98pegc2mfr(a)4ax.com...

> I've seen advice on this newsgroup to scan everything bigger than
> 3-1/2 x 5 at 300 dpi. Now I have several versions of the same school
> portrait of a child, one wallet size, one 5 x 7, and one 8 x 10. If I
> were to scan only one photo, what dpi setting should I use? Is it
> better to scan a big photo or a small photo? (I want to store it on a
> CD-R as a jpg at 90 quality)


If you're scanning a print, it probably doesnt make make
much of a difference beyond a certain size. At best, the
enlarger can only reproduce what was on the negative.
Optical defects and abberations scale with the degree of
enlargement, so there's no net gain going with a super-large
print.

In this case, I'd go with either the 5x7 or 8x10" print.

Maybe scan them both. It's possible that one was
done with more care than the other, but you will
need to look at the scans for yourself and decide.
If one has better tones, has aged more gracefully,
or has less defects, that should also be considered.

There still isn't much sense scanning any of the prints
beyond 300-600 dpi. If all you had was the wallet-
sized print, I'd say, sure, scan it at 600 dpi.


rafe b
www.terrapinphoto.com


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