Deidre Sorensen is a London UK based photographer. She specialises in maternity, newborn, and baby photography in her Kensington & Chelsea portrait studio.

Photographic print sizing: part 1 – image ratios

May 9, 2014

When my clients are choosing their favourite photos to print, I find myself walking through the relative sizes and ratios of images, and helping them think about how certain crops or images would look on their walls.  There is a lot of thinking that goes into these decisions, because it’s a surprisingly complex topic.  So, I thought I’d write a bit about it. Well, actually, a few bits:

Part 1: standard image sizes and ratios

Part 2: wall print size guide (i.e. how large will something look on a wall?)

I’ll do part 1 today and part 2 sometime in the next month or so.  

Standard Image Sizes and Ratios

While most of us rarely think about it, the height-width ratios of the images we print vary, depending on the standard enlargement we choose. We ask for a 5×7” print at the print shop, without a thought as to the original size of the image we took. And indeed, each of us has different cameras, which themselves have different aspect ratios. So the image you took with your camera and the image I took with mine may be different in their original sizes, but then we both go into the print shop and ask to print the images in the same standard size.  How does that work?

To make it easier, I’m going to start off by talking about the standard 35mm film cameras or their equivalents in the digital SLR world.

An image shot with 35mm film is in a 1:1.5 ratio (or 2:3).  In other words, when we print a 4×6” print, we print the full image, since 4:6 is the same as 2:3 or 1:1.5.  It’s the entire frame of the image that we photographed.

When we enlarge the same image to a 5×7” print, we lose a bit, since the full frame would be 5×7.5”.  We crop 0.5” off one side or the other.  If you don’t specify, the person at the print lab will make the crop decision for you.  And with a 5×7”, you might not notice so much.

But when you enlarge to an 8×10” print, you’re actually cropping quite a bit of the frame.  Indeed, the full frame would be 8×12”, so you’re cutting 2 full inches off and making the picture much more square.

Now this all gets a bit more complex when you add in other consumer cameras (or professional medium-format cameras) with different aspect ratios to 35mm film, but no matter what size the original image you take, you will have to crop it to fit with the standard print sizes, since each standard print size is a different ratio: 4×6” (1:1.5), 5×7” (1:1.4), 8×10” (1:1.25) etc.

Whatever the history of the development of “standard” sizes, all print shops follow them, and all mass frame makers create their frames this way. And so the rest of us just go along with it.

I can’t explain the reasoning behind it, but I can explain the ratios. Or give you an idea of how they compare. The diagram below shows the small and medium “standard” sizes that you’ll get for frames. 8×10” is the most square of all of them, and 4×6” the most rectangular.

common image size ratios compared in a diagram

© 2013 Studio Deidre / Deidre Sorensen, London

What does this mean?  A couple of things:

- If you’re photographing something you think you might want to enlarge and frame, it’s worth thinking about the space you’re leaving around the subject, knowing you can crop it easily.  If, at the time of taking the photo, you zoom in and create the close crop you want, you may find that cropping to fit a frame later will be a challenge.  That doesn’t mean not to think about composition and getting in close, but it does mean just thinking about adding a tiny bit extra so you have the flexibility to crop later.

- If you’re enlarging a photo at a print lab, think about the crop you want and ensure you tell them (if it’s a film negative) or adjust the crop to your liking (if it’s digital)

- And remember, if you’re not planning on putting the image into a standard frame, there’s no reason you need to be constrained by these standards.  You can simply print the full frame (e.g. 5×7.5” or 8×12”, if it’s a 35mm film or equivalent).  You may need to pay a bit extra, as they’ll print it on a larger paper sheet and trim it to size, but you’ll get exactly what you want.  Just ask at the print lab — they don’t necessarily say they do this and put it on their menu, but there’s no reason they can’t do it upon request…

Hope that’s helpful!

Part 2: wall print size guide — coming soon!

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