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-   -   Image Size, Quality and DPI relationship (https://forums.steves-digicams.com/canon-21/image-size-quality-dpi-relationship-33384/)

oldhippie Sep 10, 2004 8:36 PM



I notice that when I use photoshop to edit my images they are showing a DPI of 180.

I am using the largest size and the S (superfine) quality settings on the camera. I'm wondering if I change the settings will I increase my DPI to 300 and if so, will that provide better print quality images?

Thanks in advance for any advice.

Steve

noujwas Sep 11, 2004 6:53 PM

It's just because Photoshop doesn't know what you want to do with the photo thatit gives it a 180 resolution by default. In earlier version, I think it used to assign a 72 resolution.

If you're not printing the picture from photoshop, thenNO that 180 won't affect your printing quality.

Before you print the picture from photoshop you have to uncheck the option under the resolution(Resampling or something I forgot, I'm not in front of my computer now) and then you change the resolution to what you want. Only the printing size will change, not the screen size.

Htp

Noujwas



zonaarguello Jun 26, 2008 3:17 PM

Sorry, I have the same question::?

I bought a Canon S3 IS camera to get a large zoom camera.
Yesterday I took the same picture with the S3 IS and my old Nikon Coolpix L1 (both 6 M pixels, same light, etc) to compare them.

I found two differences in the picture properties:

1) the image size (L1: 1,3 MBS3: 2,4 MB)
2) theresolution (L1: 300 dpi,S3: 180 dpi)

could someone help me to get more resolution with the S3? I have put the maximum resolution available (2816 x 2112 px) and the superfine mode.

thanks a lot
Eliseo


Sintares Jun 26, 2008 5:15 PM

Thedpi / ppireported is just a flag and does nothing, so there is nothing wrong with the settings of your camera.

You old camera just has a setting in the file to tell your software to show the dpi as 300 the new camera has the flag set to 180.

These flags are default settings that mean nothing.. until printed out the dpi/ppi setting is meaningless.

Your photos don't have a physical size ( or pixels per inch ) until you print, they just have pixels, a height and a width.

At a resolution of 2816 x 2112 px and 180ppi the file would print out at 15.6x11.7 inches.

If however you were to print out at 9.4x7inches the pixels would be spread out so the ppi would equal roughly 300.

You can use a PPI calculator such as at http://www.mattspinelli.com/ppicalc.htmlto show roughly what ppi you would be getting at various print sizes (assuming a minimum crop of the image to fit the papers shape)

Eg for the S3 you would get

PPI for the following sizes:

4 x 6 = 469.33
5 x 7 = 402.29
6 x 8 = 352
6 x 9 = 312.89
8 x 10 = 264
8 x 12 = 234.67
8.5 x 11 = 248.47
10 x 13 = 211.2


JimC Jun 26, 2008 5:21 PM

Ignore the dpi setting you see in the image header. It's meaningless for most purposes and doesn't impact the image at all.

Some cameras put 72 in the header, some put 180; some do it differently depending on whether you're shooting raw or jpeg.

But, it's only a number that most software ignores anyway.

Here's an article that may help:

http://www.photo.co.nz/faq/resolution.htm


zonaarguello Jun 26, 2008 9:52 PM

Thanks a lot, guys, I was surprised when i saw the difference between the tags of the files:

I supposed that the amount of DPI could mean that the sensor of the L1 received more information than the other one.

See you next doubt!:cool:

Eliseo


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