Hi i always create a4 size canvas and I just noticed that when I use ruler tool to measure photo or want actual size of photo in real life to get print it's doesn't giving me the same correct size what I actually measured why ? And how to solve
This is done using the View > Print Size command. You have to set it up first.
Go to Photoshop Preferences > Units & Rulers
There you enter your Screen Resolution in Pixels/Inch or Pixels/Centimeter
I use a ruler to find the physical horizontal screen size of my monitor: 11.25 inches in my case.
Then I find the the monitor Display Resolution setting in pixels: 1280 px Horizontal x 800 px Vertical from MacOS System Preferences:
So 1280/11.25 = 113.7 Since pixels are whole units, I round it to 114 ppi and enter it here:
Click OK, and your onscreen rulers (Cmd R) and A4 document should match a physical ruler when using View > Print Size.
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One step: Choose View > Actual Size.
This is a recently added command that is intended to make the rulers match print size, by correcting for the detected resolution of your display.
If Actual Size does not make the on-screen rulers match a real ruler, your operating system or graphics hardware may be older. In that case, the older View > Print Size command still works, but requires those extra steps to set up.
"If Actual Size does not make the on-screen rulers match a real ruler, your operating system or graphics hardware may be older"
There can be a mismatch in current systems also. I use Windows 10 (v21H2), an NVidia RTX3090, and two Eizo CS2731 monitors connected via Dataport for 10 bit/channel working.
View > Actual size - slightly, but consistently, undersizes the rulers.
View > Print Size with Preferences >Units and Rulers >Screen Resolution set to 109 ppi is accurate
Yes, that does the trick on my 10 y.o. Mac. So that will be Plan A. I'll keep the older instructions as Plan B.
Thanks for chipping in, Dave. I guess it all varies depending on configuration.