OT: are 72dpi still state of the art for screen design?

[Terry Vogelaar]

Hi Tiemo,

I like to supplement to what Colin is saying, that as long as we talk about screens, there is practically no way to tell how large a pixel is. So you can fill in whatever measure suits you. On screens, the only 'true' measurement is pixels.

Currently I have an external screen attached to my iMac. The built-in one is 110 ppi (pixels per inch; dpi is only correct for printers), and the other screen is 86 ppi. Should it recalculate all measurements to compensate that difference? I don't think so, and neither do the makers of the system software. So when I drag a window from one monitor to another, I see it enlarge. 

The OS actually cannot know how large a pixel is on the monitor it is displaying on. Take LCD projectors for example. I use an 1024 x 768 pixel setting to project on a screen, but there is no way for the software to know how large a pixel on the screen is. It might be in a range between 5 and 25 ppi. 

So, you can follow the old Macintosh convention of 72 ppi, or Windows with its 96 ppi standard. Both are equally incorrect and irrelevant. Use whatever value that suits you. The number of pixels per inch only starts to matter when you print the image. Only then the dimensions of the image become measurable with a ruler.


Terry