Aspect Ratio

In analog photography with 35mm technology, an aspect ratio of 3:2 was the norm (e.g. film format 24x36mm). Derived from this film format, classic image sizes 10x15, 20x30, 30x45 appeared.

These formats ensured that during exposure only a relatively small trim occurred on the image of the negative film. Most digital SLR cameras use the well-known aspect ratio 3:2 for analog photography (exceptions e.g. Four-Third format on Panasonic and Olympus).

However, many compact digital cameras use an aspect ratio of 3:4. This aspect ratio cannot be transformed into an image format of 3:2 without being cropped or distorted. Therefore, it is crucial to decide e.g. when increasing the size, whether or not the entire photo should be visible. Then the digital aspect ratio has to be chosen. The classic image size’s aspect ratio is 4:3, which is the 15x20 format. An image with the aspect ratio 4:3 would result in the smallest trim possible. An image captured in the format 3:2 would be trimmed.

Example for image trimming (compact camera with image sensor format 4:3)


Note that by changing the aspect ratio, the maximum image resolution may be reduced. This is because in these cases only part of the image sensor is being used. The effective focal length can also be shifted.


In photographic printing or printing of an image, irrespective of the chosen format, allowance for an additional trim/trimming of ca. 2% must be included. If you wish to avoid this, you have the option of using image editing software to provide the image with a border so that any trimming only affects the added border. Additionally, specialist laboratories can provide the finished product without trimming on request. For SLR photographers this is the part of the image they see through the viewfinder as optical viewfinder seldom give you a 100% view.