If we took a picture to a frame shop, their normal approach would be to put an even mat boarder around the picture. Considering that photos are one of the most common things we want to frame, why aren't frames made with photos in mind. The ideal frame for an 8x10 photo would be 12x14, allowing for a two inch boarder on all sides. Instead, the closest standard frame size is 11x14, resulting in 1.5x2 inch boarders. Notice that an 8x10 frame is ideal for a 5x7 picture with a symmetric 1.5 inch boarder.

Of course, photos can be framed directly without a mat, but this is not a good idea because they can stick to the glass. Mats should be used to lift them off the glass, as well as dress them up.

Be sure to read how to achieve a custom look by taking into acount the aspect ratio of the photo and other tricks.