Confused by pixel dimensions and DPI? Know about knitting? Get unconfused!
Posted: Friday, July 12, 2019 12:48:05 AM
Confused by pixel dimensions and DPI?

Relax - it's explained here.

People often get confused between the pixel dimensions of an image and how dpi affects things.
What you have to realize is that dpi doesn't matter when talking about the size of an image in pixels.

It's a bit like the way knitting patterns work. If you give me a pattern that says to use 340 stitches and to knit 510 rows, how big will it turn out?
The answer depends on the size needles you use. With teeny-weeny needles it'll come out tiny (each stitch will be tiny); with huge needles it'll come out huge (and each stitch will be huge). But either way, you'll still have 340 stitches and 510 rows.

The same sort of thing applies to dpi.
If I use a printer that prints at hundreds and hundreds of dots per inch, then with a 340x510px image I'll get a tiny printout (with each dot being tiny). If I use a printer that prints at only a few dots per inch, I'll get a huge printout (with each dot being huge). But either way, there's still only 340x510px

DPI only matters when you come to output an image (=knit a pattern).

For example, on your pc screen, stuff is normaly displayed at 96 dpi. So if you were in Photoshop, viewing a 96x96px image at 100%, it would be a one inch square on your computer screen.

It doesn't matter what dpi you set up for it, it will still display on screen at 1 inch square when you're at 100% zoom.

When you come to print it, then it's a different matter. If you set the image to 360dpi, you're telling Photoshop that your printer prints at 360dpi.
If you preview what the image will look like when printed (or actually go to the trouble of printing it) it'll come out at just over a quarter of an inch.

That's because 96 pixels printed at 360 dots per inch = 2.666 0.2666 inches
Edited to add: sorry about my misplaced decimal point earlier, ack!
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