Reply To: InDesign/Prepress Myths

David – I have it here in an email that you kindly wrote me about 2 years ago – (actually might not be an email – you may have posted it in a comment or a topic on the blog – but I've never forgotten it – I could swear it's in my email though?)

You make the PPI of your images based on the square root of 2 x the lpi = ppi. So roughly 1.5 x 150lpi = 225 ppi for the images.

And you go on to state that the square root of 2 is sufficient to deal with pixels that are rotated 45 degrees.

I have never understood this – yes the square root of 2 is 1.41 – but how does that relate to pixels rotated at 45 degrees?

The answer is probably simple and I've been trying to relate it to a far more complex reasoning – but I would appreciate your thoughts on it? I've thoroughly given up on trying to figure it out – I thought the answer would come in a Eureka moment – but everytime image resolution comes up in a topic I'm constantly reminded of this conundrum that I can't for the life of me wrap my head around.