If you don't know the exact dimensions but know the ratio instead, you can use one of the 16 ratio modifiers, which include [common aspect ratios in still photography](https://en.wikipedia.org/wiki/Aspect_ratio_(image)#Still_photography):
+If you don't know the exact dimensions but know the ratio instead, you can use one of the 16 ratio modifiers, which include [common aspect ratios in still photography](https://en.wikipedia.org/wiki/Aspect_ratio_%28image%29#Still_photography):