The "aspect ratio" of a photo is the relationship between its height and width. For example, a square image has an aspect ratio of 1:1 - the width is equal to the height.

Aspect ratio is important when we print a photo in a standard size - 4 x 6", 5 x 7", 8 x 10", 16 x 20", 20 x 30", or Wallet-size. As long as the relationship between your image and the chosen print size is standard for the height and width of the photo, the entire image will fit on the print. If the dimensions of the photo are too tall or too wide, or square, the image will not occupy all the space on the print.
The following aspect ratios are standard:

· For a 4 x 6" print, your photo should have an aspect ratio of 1:1.5.

· For a 5 x 7" print, your photo should have an aspect ratio of 1:1.4.

· For an 8 x 10" print, your photo should have an aspect ratio of 1:1.25.

· For an 16 x 20" print, your photo should have an aspect ratio of 1:1.25. (same as 8 x 10")

· For an 20 x 30" print, your photo should have an aspect ratio of 1:1.5. (same as 4 x 6")

· For a Wallet-size print, your photo should have an aspect ratio of 1:1.5. (same as 4 x 6")

What is a pixel?
Pixels are the basic building blocks of every digital image. Digital images are comprised of pixels lined up side-by-side, both vertically and horizontally. If the image is made up of many small pixels, it will look smooth and crisp. If it's made up of fewer large pixels, the image will be jagged and unclear, or pixilated (see example). This translates directly to print quality - the more pixels in your photos, the better the prints will look

How are pixels measured?
The number of pixels captured by your digital camera's electronic chip is measured in terms of resolution. High resolution images are made up of more pixels than low resolution images (and thus result in better prints). Cameras' maximum resolutions are usually clearly indicated on the packaging or even on the camera itself. If your camera has a resolution of 640 x 480 pixels or lower, it's considered a web camera and is best used for viewing images on a computer screen rather than making photographic prints. If your camera has a resolution listed in "megapixels" (millions of pixels per image), then it's suitable for getting prints

How do I set my camera's resolution?
Most digital cameras give you a choice of settings for image resolution. Photos taken on lower resolution settings take up less room on your memory card, but will not result in the best prints. For the best results, we strongly recommend always using the highest quality JPEG setting on your camera. Getting a larger memory card is a much better option than unsatisfactory, pixilated prints. See your camera's owner's manual for more information on the specific resolution options and how to set them.

How else can I affect the quality of my pictures?
There are other ways you can affect the quality of your digital photos. For example, using the digital zoom function on your camera will result in lower resolution images. Unlike the traditional optical zoom, digital zoom is a software program that simply doubles the size of the pixels every time you zoom in. The result is fewer pixels, not a magnified image. You can also reduce image quality after taking the picture by cropping the photo. Similar to digital zoom, the tighter you crop the image, the more the pixels you remove, ultimately decreasing the quality of your final print. A better option is to get close to your subject when you take the photograph so cropping isn't necessary. Unfortunately, you can't increase resolution once the picture is taken, so remember these tips!