Why Do My Scanned Image Files Report Different Resolution Properties

[Peter D]

After scanning some test slides (same image at 200 dpi x 1200% scaling and
2400 dpi x 100% scaling), I loaded the resulting saved images in the old MS
Photo Editor (my default JPG viewer) and noticed that the resolution was 300
dpi regardless of what I used for scanning. So I opened Corel Photo-Paint 9.
A check of the properties says "72 dpi" regardless of what I used for
properties. What is going on? I need to make sure that I can scan and
achieve the max resolution for these slides because they are old and there's
a lot of them. Any suggesitons are welcome.

 

[Steven Kefford]

After scanning some test slides (same image at 200 dpi x 1200% scaling and
2400 dpi x 100% scaling), I loaded the resulting saved images in the old MS
Photo Editor (my default JPG viewer) and noticed that the resolution was 300
dpi regardless of what I used for scanning. So I opened Corel Photo-Paint 9.
A check of the properties says "72 dpi" regardless of what I used for
properties. What is going on? I need to make sure that I can scan and
achieve the max resolution for these slides because they are old and there's
a lot of them. Any suggesitons are welcome.

A ppi, or to be more precise, ppi(pixels per inch), tag in an image file
is a meaningless piece of information that is assigned to the file. It
has no impact on file sise or resolution. The only thing that makes any
difference is the number of pixels, not pixels per inch. A file does not
have a dimension that can be measured in linear units, so it can't have
ppi. A print of that file is altogther different.

Steve

 

[Maris V. Lidaka Sr.]

The total number of pixels horizontally and vertically are what is
important, and they are probably the same in MS Photo Editor and in
PhotoPaint 9.

Read up on resolution at Wayne Fulton's excellent site:

http://www.scantips.com/no72dpi.html

Maris

 

[Bart van der Wolf]

The total number of pixels horizontally and vertically are what is
important, and they are probably the same in MS Photo Editor and in
PhotoPaint 9.

That is correct. Pixels is all that counts.

Read up on resolution at Wayne Fulton's excellent site:

http://www.scantips.com/no72dpi.html

Overall excellent site, but horribly confusing as a result of the
incorrect usage of DPI where PPI should be used. But that subject has
been discussed, often, and again extensively in a recent thread called
"Scanning film".

Bart