Apple Preview—question

[clyde]

Thanks for the info. In System Info the graphics display of this 21-inch iMac is said to be 1920 x 1080

I see that 2560/3840 = 0.66666 in the example of the 27-inch Retina display.

What numbers apply to this 21-inch monitor? If it's 1920/2560, that's 0.7245, but if the ratio is 1920/3840 the ratio is 0.500. Must be the former…

Or where did I go off the rails?

Thanks!