Pixels, Megapixels and Size OR Why My Email Photos are HUGE!!!

Megapixels - millions of pixels or picture elements. Each pixel is part of the image your camera takes. The millions of them together form a gigantic mosaic to form the image.

The image size really refers to two different concepts:

• the size of the image on a screen or monitor and
• the size of a printed paper photograph

Monitors or computer screens display 72 dots per inch (dpi). So if you want to know how large an image will be on a computer screen, divide both dimensions by 72. For example, suppose you have a digital photo which is 3000 x 2000 pixels or a 6mp image.

3000/72 is about 42 inches and 2000/72 is about 28 inches. So that 6mp image needs a computer screen which is 42 inches wide by 28 inches high.

Did you ever wonder why the photos your friends email you are so big? It's because they are viewing the image on their computer using some program that reduces the picture to a size convenient to the screen. They don't realize the amount of space that image needs on your screen when you view it in an email.

When you go to print a photo either at home or commercially think about dividing by 200 instead of 72. When you print on paper the common value used is 200 dpi for a top quality image. (You may hear 150 or 220 or even 300; it's just different opinions being expressed.)
So that 3000 x 2000 or 6mp image comes out at 15" x 10 ". Now the thing to remember here is that the 15" x 10" represents the LARGEST top quality image you can print. There is no problem at all in printing smaller images - 4x6 inches or 5x6 inches or 8x10 inches or even 11x14 inches. It's when you start getting too much above the 10x15 inch size that you will start noticing that your picture quality suffers.

p.s. You may hear this same discussion with the titles "The Rule of 72" and "The Rule of 200".