megapixels.
© 2002 Jamie Zawinski <jwz@jwz.org>

The word I hate today is:

"Megapixels."

How did this asinine, obfuscated word get into the vernacular? What was wrong with "X by Y"? I'm sorry, I'm one of those poor, pathetic people who is not good at doing fucking square roots in his head.

Of course this is mostly a rhetorical question: I'm pretty sure the answer is ``because it allows small increases in resolution to look enormous.''

But I guess we're just lucky they didn't re-use "DPI" to talk about cameras in some arbitrary, braindead Apple-like way. Actually, that might have been easier to understand.

You can compute ``resolution'' from ``megapixels'', of course, but it's a gigantic pain in the ass (a megapain?) If a "3 megapixel" camera takes a 4:3 picture, then the image will be somewhere around 2048x1536 (equals 3,145,728). At 300 pixels per inch, 2048 pixels is 6.8 inches (2048/300). So with that camera, you can get an image that can't be printed larger than 6.8"x5" if you require 300dpi.

WASN'T THAT EASY?

It's easy to get from ``X by Y pixels'' to ``physical size at N DPI''. It's a pain in the ass to get from megapixels to, well, anything, because finding factors of large numbers is hard.