Digital Advent Calendar 2010 - Day 11

Aspect Ratios

The 6×4-inch print has been the standard sized photograph since I can remember.   The size came from the fact that a 35mm negative (remember those?!) measured 36mm x 24mm.  The common theme here is termed the ‘aspect ratio’ which sounds quite complicated but is quite simple in principle.

The aspect ratio of a digital photograph is the relationship between the width and height of the photograph.  The two most common ratios are 3:2 and 4:3.  The first number represents the width of the image and the second number represents the height.  Both numbers are not indicating the measurement but rather a relationship.

The 36x24mm negative measurement has a 3:2 ratio.  A 6×4-inch print also has a 3:2 ratio.  This means that when a 6×4-inch photo is made from a 35mm negative the full image is shown on the print.  The problems arise when we try to print a 7×5 or any other standard print size that doesn’t have a 3:2 ratio.

For some reason when digital cameras were introduced the designers decided to use an aspect ratio of 4:3 with mainstream digital cameras compared to the standard 3:2 which had been the norm for so long.  As a result, to get a full image without any cropping from a digital image, the smallest standard sized print is 8×6.

It is important that you are aware of the aspect ratio issue whether you print at home or send your image to a lab.  What you see on the back of your digital camera is not necessarily what the finished print will look like depending on the print size and consequent aspect ratio.  I suggest that you crop your images to the desired final output size prior to printing/sending to a lab so that you know exactly what the finished print will look like.

So, what happens when the aspect ratio of the photo produced by your digital camera does not match the aspect ratio of the print? What happens when you print an image that is 3:2 ratio at 7×5-inch or 10×8-inch print size? Your image gets cropped to fit the aspect ratio of the print.

© Ben Mullay Photography. All Rights Reserved.

Original 3:2 image

© Ben Mullay Photography. All Rights Reserved.

7×5-inch Crop

© Ben Mullay Photography. All Rights Reserved.

10×8-inch crop

The images above illustrate what happens to the original image which you’d see on the back of your digital camera when printed at non 3:2 ratio standard photograph sizes.

I hope this clears up an issue that I often find myself explaining to people.  If you have any questions then please leave a comment below.

-Ben