photoshop default dpi

when i open an imag ewith photoshop and go to
image size
i find that the dpi by default is 72 px.

can i make it open all the photos at 300 px. resolution so i start editing them accordingly.
or the resolution (72 px) is part of the file that i am opening and it can't be changed, unless i do it manually..

Thank you
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Peter HartCommented:
the 72 DPI is the usual screen resolution.  if you have a photo that is a "high res" then
the higher the res,  the larger (width and height) the image will be.
so I can open up a photo from my canon and its 72 DPI, but the size is 2588 Pixels x 3888 pixels.
if you adjust the DPI the size of the image adjusts, but in photoshop you can zoom in or out.

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Dan CraciunIT ConsultantCommented:
The file has the resolution information included. Photoshop simply reads it and displays accordingly.

You can record a macro/action and assign a shortcut key for it if you find you change the resolution over and over again.

PS action
Dave BaldwinFixer of ProblemsCommented:
Note that changing the DPI will alter the file.  That isn't always what you want.  Note that web browsers essentially ignore DPI settings in images.  The images are displayed pixel for pixel unless you tell the browser to do something else.
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I think what the OP is asking is why do images from a digital camera open in photoshop at 72 dpi.

If this is the question that is the default set by the camera. The camera will save an image at 72 dpi distributing the x and y pixels at the density described in the dpi.

The pixel count/dpi/ppi doesn't affect the total x and y pixel counts until an image editing application removes or adds pixels through sampling or scaling. AN example might be  an image is 1000 pixels wide by 1000 pixels high. The file opens in photoshop at 100 dpi so the file is currently (real world dimensions, not screen dimension) approximately 10 inches square. When the image is resampled to 300 dpi the image becomes 3.33 inches (approx) square.
Dave BaldwinFixer of ProblemsCommented:
In my copy of Photoshop, if you change the DPI, the Document size stays the same but the number of pixels adjusts to the change in DPI.  I have an image that is 296x166 at 72DPI.  If I change the DPI to 300, the pixels change to 1233x692 while the width and height in inches stays the same.  If I click on OK, the image will be resized to 1233x692.
Dan CraciunIT ConsultantCommented:
You need to uncheck "Resample image". That way the pixel count will be the same, only the dpi and print size will change.
image size
Dave BaldwinFixer of ProblemsCommented:
The default action in GIMP is to change the document size when you change the DPI and leave the pixel sizes alone.
…essentially if you resample you add pixels and scale you omit/delete pixels. Changing the DPI (however and in whatever application) just changes the sample or density of pixels.
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