
Originally Posted by
anon
Then, if I wanna print both pictures on an A3 format (I'd need a 300 DPI picture at least) I should expect a slightly different quality between the 2 prints. Is that correct?
Yes. That's correct. There's one other concept you'll need to master called "Interpolation". Think of interpolation the same as using an enlarger in a darkroom. When you check that "Resample Image" box and then key in a higher resolution, Photoshop will enlarge your image. What's Photoshop doing? It's using a mathematical formula to create pixels that weren't there before and your image will grow in size.
Now, if you do NOT check that Resample Image box Photoshop will not resize the image for you and will not add pixels that didn't exist before.
Why would you want to add pixels that aren't there? Well let's say you want to print a really large print - say 13X19. You have two choices: Print it at a low resolution, say 180 dpi. To do this you would NOT check that "Resample Image" box and Photoshop will NOT add pixels.
But you may find that the quality of the print isn't very good when printed at 180 dpi. So your other option is to use interpolation or enlarge the print by having Photoshop add pixels.
This is usually a two-step process: First, UN-check the Resample Image box. Next, enter say 300 dpi in the resolution box. Now, CHECK that box and tell Photoshop to increase the image by say 110 percent. The 300 dpi will stay the same but your image will grown in size when you press enter. This is confusing, I know. The best thing to do is fool around with the Image>Resize Image dialog box 'til you get the hang of it. Good luck!