Understanding Aspect Ratio
 
5×7. 8×10. 4×6. 12×12. What do these numbers have in common?
They are all sizes that we commonly use for printing images, right? 
 
They are also Aspect Ratios.
 
Aspect ratio is the proportion of an image’s height to its width. Most cameras have the ability 
to produce images in one and only one aspect ratio. And for most photographers with SLRs this 
ratio is 2:3. That means that the height of the camera’s images is 2/3s of the width.
 
That’s simple enough, right? Next, let’s replace “units” with “inches.” We can print the image 
above as 2×3 inches. But who wants a wallet size of the photo? Let’s double the size to make it 
4 inches tall by 6 inches wide or let’s double it again, to 8 inches tall by 12 inches wide.
 
Wait a minute. You skipped right over 8×10. That’s the size I want for printing this image.
 
The aspect ratio of an 8×10 is 4:5. That means that it is 4 units high by 5 units across. How do I 
know? I divided 8 by 2 (=4) and 10 by 2 (=5). 4:5 is not the same as 2:3. Who said photography 
wasn’t a science? :)
 
So how do you get an 8×10 from an 8×12? Well, you have to crop those extra two inches off 
the side, right? And you are going to lose 2 inches of your image. There is no way to avoid 
that.
 
What happens if you want to go from a 4×6 to a 5×7? Can’t you just add an extra inch on to 
each side? No, not unless you want to distort your image. 
 
This is the answer to that age old digital photography question, “Why do I have to crop off part 
of my image if I’m going from a small photo (4×6) to a larger one (8×10)?”
It’s not about the size of the photo; it’s about the aspect ratio.
 
Now that we’ve covered that, let’s list the common aspect ratios and their corresponding print 
sizes.
 
2:3 – 2×3, 4×6, 8×12, 16×24, etc.
4:5 – 4×5, 8×10, 16×20, 24×30, etc.
5:7 – 5×7, and that’s about it.
1:1 – a square. Common sizes are 5×5, 12×12, 20×20
 
Here’s a visual example: