Crop Factor

Black – Full Frame

Red – 1.3x Crop Factor

Yellow – 1.5x Crop Factor

Green – 1.6x Crop Factor

If you take a photo with a smaller sensor and the same lens it will only show a smaller area of the scene. Until recently full frame cameras were DLSR's and lower end cameras had smaller sensors. When you enlarge images to the same size from different sensors the ones with the smaller sensors will be enlarged more, making it seem bigger, when adding a larger lens to a smaller sensor, the lens is often said to have a larger lens size. Bellow is  a table to show different lens sizes for different crop factors. The column on the left is the lens focal length on a full frame camera.