This week, I have a confession to make: I stink at math. I’m not just talking calculus or higher math. No, I mean every type of math. Put a math problem in front of me and I’ll find a way to mess it up. I am NOT the person you want anywhere near anything having to do with numbers.
In fact, one of my most vivid memories of kindergarten is looking at a number three and deciding that I really was afraid of threes. Twos were okay, but threes made me nervous. Having decided that, I gravitated back to the phonics exercises. (Yeah, for some of us, math phobia started really early.)
I still have a personal trauma every time I have to determine which stupid little sideways V is the greater than sign and which one is the less than sign. I’ve actually had math class nightmares about that kind of thing. It’s like that old cliché dream where you are called up to the front of the class to solve some labyrinthine problem on the black board. Some people dream they are naked. For me being hopelessly mathematically impaired is embarrassing enough.
So given this mental limitation of mine, it should come as no surprise that I screwed up the math in last week’s Tales from the Mousepad article about e-mailing images. Originally, I said that if you have "two images that are the same size (height and width) and one image is 400 dpi (dots-per-inch), and the other is 200 dpi. The 400 dpi image has twice as much detail as a 200-dpi image because it has twice as many pixels."
I was wrong.
Fortunately, I got the following from an astute Logical Tips reader named Bill:
"An image at 400 dpi will contain 4 times as much information as a 200 dpi image if all else is equal."
The reason is that 200 x 200 = 40,000 dots versus 400 x 400 = 160,000 dots.
I promised Bill I’d confess my mistake and correct it in the archive on the Logical Tips site (http://www.logicaltips.com). And when you do the math correctly, it emphasizes even more why it is really important to scale down those images *before* you e-mail them 😉