The various formats for photos

Quite confusing for beginners is the matter about the different formats and sizes that are offered by online printing companies. Often you can choose from two or more formats which are actually one size. The reason being is that the aspect ratio has changed for digital cameras: For analogue pictures, the ratio is 2:3, whereas pictures taken by digital cameras use the ratio 3:4. There is the odd camera which is still able to use the "old format" but for the majority, the digital format is used.

If you want to have a picture of the new digital format in the old analogue format (which is bigger in size and even cheaper at many printing services), the picture has to be cropped before the photo development: