Why do my image sizes keep changing

[paulloseby]

I'm using Photoshop 2.0.1 on a Mac running OS Monterey

I set a size for the image but then, whenever I do anything, that size changes.  I can set the image size at 297mm x 211mm and then, after I have made any alteration to the image, it changes to a totally different size (have attached an example).

Can anyone please tell me what the problem is or what I am doing wrong?

Many thanks

Paul

[D Fosse · Accepted solution]

You need to watch the pixel dimensions. Photoshop basically has no concept of "size" - it only works with pixels. Pixels have no size, they are just data points.

A physical size is set by the simple formula "pixels per inch" (ppi). Setting a ppi number translates from pixels into a physical size.

Uncheck "resample image"! This uses the ppi number to scale the image up or down. In effect, it reverses the formula.

In short - as long as the pixel dimensions don't change, the file itself is unchanged. The key to unlocking this whole thing is in those three words: pixels per inch. It means exactly what it says.

[paulloseby]

Many thanks for that.  I'm now 73 and try to keep up with technology etc but sometimes, I appear to be a little slower on the uptake.

I do appreciate your help

Kindest regards

Paul

[MARKETING22904268o6q7]

omg, you just explaned my years old question. i guess i was using points and inches in PC, but i was using pixel in MAC. and i thought for years it was MAC prob! THANK YOU!!!!!!!!! i had to leave the comments for ya.