I think it will be an easy question…
I always set the image resolution to 72 (ppi) when using Photoshop,
Because that’s how I learned it.
Web image : 72 / Print image : 200~
So all my resources at the time had a resolution of 72.
ex, [@2x] 140140px , 72ppi [@3x] 210210px, 72ppi.
Today, I discovered a difference in figma.
Figma multiplies the resolution when exporting the image.
ex, [@1x] 7070px, 72ppi [@2x] 140140px , 144ppi [@3x] 210*210px, 216ppi.
So I wonder why figma multiplies resolution.
Unlike Photoshop, when it multiply the resolution,
doesn’t a problem occur on mobile? Or is it always better?
So what we are working with in figma are not pixels*(you can of course switch to pixel mode)*, these are vectors. If you start to design for example a mobile app the best way is to start with 1x (72ppi) so you can control element sizes better like typography and iconography, otherwise a 16x16 icon is 32x32 and a 32x32 icon is 64x64 and so on, because you start designing in 2x so doubled the size of you initial screen and you need to divide it in the export again, it gets pretty confusing and you have a better base for an export later on (and no giant screens flying around in your file)
So if you use an iPhone 13 Pro, the 1x screen dimensions are 390x844, but because the ppi are 460 the resolution gets 2532x1170 (3x) at the end, the good thing is that we work with vectors as I said, so scaling is not a problem if you export icons for example as svgs (that explains also why your screen looks crisp in the figma mirror app even if your frame is 1x), but if you export something like a splashscreen, because some dev want’s to have an image, you need to scale it up so it won’t get blurry. It’s also that if you communicate for example text sizes you give the “base” size like 16pt and not 48pt, just because you designed your app with a 3x frame in figma doesn’t mean these are all the right sizes, the pixel density is just getting higher not the element bigger.
But to be clear if an image is 200x200px it doesn’t matter if it’s 72ppi or 300ppi it will be always 200x200px and takes the same space, we are not doing print work here. (but of course you could in figma) So it’s a huge difference if you use a 390x844px or a 2532x1170px image.
I hope it makes things more clear.
Have great day