Aspect Ratio (pdf)

Whenever some-one asks me about printing their photos, the conversation usually includes a discussion about "Aspect Ratio". At this point, most people look at me with glassed over eyes expecting a technical treatise.

Well, really this is a simple concept: Aspect ratio is the relationship between the "width" of an image and it's "height". So, if an image is 4 inches wide and 3 inches tall this is expressed as 4:3 ratio. This is exactly the ratio of point-and-shoot class digital cameras. You can think of it as the "shape" of the image. It is ALWAYS expressed as width:height (width first, height after) and if you look carefully at your camera, the width is more that the height, so this makes sense.

Anyone can view these photos satisfactorily on their standard monitor or television because these devices use the same ratio. Where we confront difficulty is in printing the photos because we have all become accustomed to a slightly different aspect ratio - that of the 35mm FILM camera. These cameras use a ratio of 3:2, that is an image that is 3 inches wide is 2 inches tall. This is perfect if we are making 4x6 prints - the ratio is 3(6 divided by 2 = 3) to 2(4 divided by 2 = 2) and every photo album in every home contains 4x6 size photos, a tribute to the success of 35mm cameras. And, again, if you look at the "shape" of a 35mm film frame, the width is more that the height, again making perfect sense.

OK, this does not sound like a big deal, please make 4x6 prints from my digital camera.

This works most of the time. Where there is a problem is with the subject that has been captured very close to the edge of the frame in photos taken in horizontal orientation. The lab returns your photos and the top and bottom of your subjects has been cropped and that's not what you wanted. The immediate reaction is the lab has cropped your photos badly and they should fix the problem because you don't want this to happen again. Bad lab, so you go to another lab and the same problem occurs again. What is going on??

Take a look at these photos and you will immediately see where the problem lies.

Image as taken by camera

4x5.33 inch print on 4x6 paper. Note the white borders at left and right.

4x6 inch print from the same original. Note cut-off at top and bottom.

When asking for prints from your point-and-shoot digital camera, you need to specify "No Cropping" to avoid any cut-off in your photos.

Wait a minute, you did that, you specified "no cropping" and your lab printed your photos and they aren't 4x6, they are some other size that no longer fits your photo album. They are 4x5.33 inches and they have these white borders but only on 2 sides. That's not what you wanted.

And what does 4x5.33 have to do with my digital camera, anyway?? This doesn't make any sense.

Well, hold on for a second - if you do the math, you will see that the 4x5.33 inch print is the same ASPECT RATIO as the 4:3 ratio in your point-and-shoot camera except that it's shape is expressed the other way round - height:width and this is the source of the confusion because it's not easy to mentally convert from one expression to the other. Especially when you are looking at the photo and it's 5.33x4 inches. Ah, it's clear now - 5.33x4 is the same SHAPE as 4:3.

Incidentally, the DSLR digital cameras use the same aspect ratio as the 35mm film camera, so this discussion never comes up with these cameras when making 4x6 size prints.

Article © 2009 by Alan Barry Ginn