We are often asked about the resolution of pictures that will go into a scientific poster. Here’s a primer.
First of all, you need to know how many pixels your picture has. Pixels are the little squares of color that make up your digital picture. Our goal is to use enough of them that the individual pixels are not noticeable.
In Windows, just hold your cursor over the file name and it will tell you the dimensions, which is the number of pixels in each direction. You’ll see a number like 1200 x 1600, which means the picture is 1200 pixels in the short direction, and 1600 pixels the long way. On a Mac, do file>get info (or Command i) with your file highlighted, and it will give the dimensions.
We like to see pictures printed at a minimum of 72 dpi, and 100 is better. That 1200 x 1600 image at 100 dpi is 12×16 inches in size (dpi means dots per inch, and a pixel is the same as a dot). At 72 dpi the same picture is 16.7 x 22.2 inches. So, if you are going to use that 1200 x 1600 photo on your poster, it’s best not to make it any bigger than that. If you were really stuck, you could cheat down to 50 or 60 dpi, but you’ll start to see the “stair-step” effect around what should be sharp edges.
Be sure your camera is set to take pictures of high enough resolution before you start!