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Old Jun 3, 2010, 10:57 AM   #1
Join Date: Jun 2010
Posts: 63
Default canon sx120 resolution question....

i bought a canon sx120 yesterday. i noticed at 10mp, when i open the files in photoshop they are only 180 dpi. i had a 7 mp cam that opened in photoshop at 480 dpi. is there a setting on the cam that changes that or is that just the max quality of the photo? it seems kind of confusing to me for the res in photoshop t be smaller from a higher mp camera.
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Old Jun 3, 2010, 11:47 AM   #2
Join Date: Jun 2003
Location: Savannah, GA (USA)
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It's just a number in the image header, and it's ignored by most software entirely. Many cameras plug in 72 dpi by default. ;-)

The actual pixels per inch you are sending to a printer will depend on the image size in resolution and the print size you need (since you're spreading the same number of pixels over a larger area for larger prints, resulting in less dpi).

For example, if you wanted an 8x10" image at 300dpi, you'd need to send an image size of 3000 x 2400 pixels (7.2 Megapixels) to the printer.

8 inches x 300 dpi = 2400 pixels
10 inches x 300 dpi = 3000 pixels.

But, if you tried to take that same 3000 x 2400 pixel image and print it at 16x20 inches, you'd end up with only 150 dpi:

2400 pixels / 16 inches = 150
3000 pixels / 20 inches = 150

It's just a number in the image header. Some cameras plug in 72 dpi, some plug in 240, some plug in 300, etc. But, it doesn't mean a thing to most software.

Hardly a month goes by when someone doesn't get upset because their new camera is taking images at only 72dpi. :-)

Again, it's only a number placed in the image header and the dpi you get from a given image size will depend on the resolution of the image in pixels (width x height), and the print size you need.

Here is an article that may help to explain it:

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Old Jun 3, 2010, 2:31 PM   #3
Join Date: Jun 2010
Posts: 63

so, if i resize the image up too 300dpi and change the image dimensions to 5 by 7, do i gain image quality? or is the quality going to be the same regardless of the resolution?
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