Computer Graphics with Photoshop - dpi changes when saving

Author

dpi changes when saving

Lex

2004-10-02, 12:14 pm

I have a strange Photoshop issue. I have a file in 300dpi. When I save
it as a gif or jpeg and then open that file, suddenly the file is in
72dpi. How come and how to get it in 300dpi?

Tom Thomas

2004-10-02, 12:14 pm

lexouburg@hotmail.com (Lex) wrote:

>I have a strange Photoshop issue. I have a file in 300dpi. When I save
>it as a gif or jpeg and then open that file, suddenly the file is in
>72dpi. How come and how to get it in 300dpi?

The dpi setting of an image is only applicable to printing. GIF files
are not intended for print and the file format does not support a dpi
setting.

JPG files are also not intended for print; however they will retain a
dpi setting if you save them using the FILE>SAVE AS option. If you
create your JPG using "Save for Web" then the dpi information will be
discarded because "Save for Web" means just that -- save it for
display on the web, not for print.
-------------------------------
Tom

Unsolicited advertisements cheerfully ignored.

Johan W. Elzenga

2004-10-02, 12:14 pm

Lex <lexouburg@hotmail.com> wrote:

> I have a strange Photoshop issue. I have a file in 300dpi. When I save
> it as a gif or jpeg and then open that file, suddenly the file is in
> 72dpi. How come and how to get it in 300dpi?

Do you use "Save for web"? If you use "Save as" that shouldn't happen.

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl/

Tacit

2004-10-02, 12:14 pm

>I have a strange Photoshop issue. I have a file in 300dpi. When I save
>it as a gif or jpeg and then open that file, suddenly the file is in
>72dpi. How come and how to get it in 300dpi?

All GIF files are always 72 pixels per inch. (Note: Forget the misleading and
incorrect language scanner makers make; your images are measured in "pixels per
inch," not "dots per inch.") The GIF standard does not permit saving a GIF
image with any other resolution.

Your JPEGs are probably 72 pixels per inch because you are using Save for Web,
which removes resolution information.

The question is, why is it a problem? If you are saving an image for the Web,
the resolution makes no difference and is ignored. Only the *total number of
pixels* matters. On the Web, a 320x200-pixel image at 72 pixels per inch is
identical to a 320x200-pixel image at 300 pixels per inch, which is identical
to a 320x200-pixel image at 6,000,000 pixels per inch.

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

Xalinai

2004-10-02, 12:14 pm

Tacit wrote:

>
> All GIF files are always 72 pixels per inch. (Note: Forget the
> misleading and incorrect language scanner makers make; your images
> are measured in "pixels per inch," not "dots per inch.") The GIF
> standard does not permit saving a GIF image with any other resolution.

I'm sorry to say that but you're writing nonsense here.

GIF do not have any DPI information and PS simply shows a default value.

> Your JPEGs are probably 72 pixels per inch because you are using Save
> for Web, which removes resolution information.

Result as above: PS shows default DPI value instead of saying "there is
no value set for this image".

Michael

Johan W. Elzenga

2004-10-03, 11:14 pm

Xalinai

2004-10-04, 11:14 pm