Written by Gerry Gerling
Aspect ratio is the relationship of the width of a picture or sensor in relation to the height.
A picture which is twice as long as it is high would have an aspect ratio of (2:1) (read 2 by 1) So this picture could possibly be 4 inches by 2 inch, 8 inches by 4 inches, 16 inches by 8 inches etc. As long as the length is twice the height, the aspect ratio would be (2:1). In this tutorial I will show aspect ratios in brackets so they will not be confused with print sizes. Aspect ratios almost always are shown in the lowest possible whole number stating the longest side first.
The most common print sizes in inches (along with the aspect ratios) are: 4X6 (3:2) 11X14 (14:11) 5X7 (7:5) 12X18 (3:2) 8X10 (5:4) 13X19 (19:13) 10X10 (1X1 16X20 (5:4)
The most common sensor aspect ratio for DSLRs is (3:2).
The sensor of a full frame camera has the dimensions of 36 X 24 mm and to get the lowest possible whole number, you would divide each side by the lowest common denominator which in this case is 12.
36 divided by 12 = 3 24 divided by 12 = 2 therefore the aspect ratio is (3:2).
In the case of crop frame cameras, Nikon, Sony, Pentax, Fuji etc. have a sensor size of 23.6 X 15.7 mm so the aspect ratio is also (3:2).
Canon has a slightly smaller sensor (22.2 X 14.8 mm) but the aspect ratio is still (3:2).
Most bridge cameras have an aspect ratio of (5:4) which is the same as a standard definition TV and a CRT (not wide screen) computer monitor.
Why should aspect ratio be a concern? 1. If you will be printing your pictures you will have to be sure that you crop them to the same aspect ratio as the print size that you want. Some people say "when I take my pictures to Walmart and ask them to make 8X10 prints they don't give me the whole picture, Jimmy's arm is cut off." Of course it is, if the aspect ratio of the digital file is (3:2) and the aspect ratio of an 8X10 print is (5:4), some of the width of the picture must be eliminated. The next slide shows how much of your (3:2) frame will be chopped off when you change the aspect ratio.
[email protected] Remember that cropping to a different aspect ratio will result in some of the frame being chopped off so don't make your composition too tight when you take the picture. You will have noticed that very little is chopped off your (3:2) image when you changed to (7:5). Those who print 13X19 will also have very little chopped off. Some cameras allow you to set the aspect ratio in which your pictures will be recorded on your memory card.
If you will not be post processing your pictures and you know the size that you will be printing them (e.g. snapshots) then it makes sense to set your camera to the aspect ratio which corresponds to the print size. Or, if you intend to show your pictures on your wide screen TV then set your camera to an aspect ratio of (16X9).
If you will be post processing your pictures (and we all should) it is best to keep your camera set to its native aspect ratio (largest number if pixels) because you can easily crop in post processing.
2. The second reason to select a different aspect ratio is to suit your composition.
For example if your landscape picture does not have a very attractive sky or foreground you should choose an aspect ratio which is significantly wider than it is high, eliminating the features that do not add to the picture and emphasizing those in the middle. But remember that if you are going to use a standard mat and frame you should stick to the common sizes that I previously showed.
3. Another example would be changing the aspect ratio to tighten in on the subject as I will show in the following examples.
The first picture is 'as taken' with an aspect ratio of (3:2). I have lightened the shadow on the model's face in post.
There is quite a bit of excess negative space in the top of the picture so I am going to crop it. let's try cropping it for an 11X14 inch print {(14:11) aspect ratio}. This looks better.
I now want to show you how little difference there is between a (14:11) aspect ratio and a (5:4) aspect ratio. You can see that there is very little difference between and aspect ratio of (14:11) and (5:4).
Now let's see if we can improve the composition by changing the (5:4) aspect ratio from portrait to landscape orientation. In Photoshop I chose a width of 10 in. and a height of 8 in. I could have chosen a 4X5 in. print or a 16X20 in. print because the aspect ratio would still be (5:4).
This gave me the following composition.
So you see that I have tightened in on the subjects, eliminating everything that was not necessary The subjects are as large as possible while still leaving sufficient negative space for framing
While most post processing software will allow you to crop, not all will let you dial in the crop size. You will be allowed to crop horizontally and vertically but you will have to judge the width to height relationship. In order to crop to a certain aspect ratio you can try this procedure.
After you have made your crop, roughly showing the image that you want at an approximate aspect ratio that you have in mind, use a plastic ruler (so as to not scratch your monitor screen) and measure the dimension which is most important to your final crop.
Let's assume that you have measured the width at 11 inches and you want an aspect ratio of (5:4).
Set up a simple ratio equation like this showing the height as x: 5 = 11" 4 x" so cross multiplying you will get: 5x = 4X11"
and solving for x: x" = 4X11" = 44" = 8.8 inches 5 5 Now just adjust the crop height to 8.8 inches using your ruler on the screen and your picture will have a (5:4) aspect ratio.
If you Google ASPECT RATIO FOR PHOTOGRAPHY you will find aspect ratio calculators in which you plug in the known numbers and it will give you the aspect ratio. I have never used them but you can explore them if you wish.
Now that you know everything that there is to know about aspect ratio you can crop intelligently, improve your composition and be able to make prints which will include everything in them that you want.
Aspect Ration picture from [email protected]