On Photo Cropping

Photography is so much about the process. I no longer develop my own film and prints eliminates all but a few hours of anticipation.  Now I take the image, see it immediately, play with it, send it off to the printer… and sometimes have to wait 8-10 days before I can hold it in my hand.  I rip open the package, toss to the side the index print card and… see that my head is cut off.  What happened?

What is Photo Cropping?

It’s a little off the top.  And sometimes the sides.  Cropping is a tool used to remove extraneous information from a picture, like that strange guy in the red baseball hat throwing a frisbee behind you in that beach snapshot.  He can go.  Sometimes it’s used for artistic purposes, to draw attention to a subject.  Sometimes, cropping refers to cutting down an image to a printable size.

Why is cropping necessary?

Standard print sizes are as follows:

Wallet (2.5″x 3.5″), 3.5″ x 5″, 4″x6″, 5″x7″, 8″x10″, etc.

The problem is that DSLR sensors these days have a ratio of 3:2 meaning that in order to print everything your camera sees in the viewfinder you need to choose a size that matches the ratio.  This is why 4×6 prints are the most popular size in America and often the least expensive print size available.  The next standard size print to give you the same print area is a 20″x30“!

But why? You may ask.  If print sizes are popular because of sensor size, then one or the other should adjust!  Well, yes, I think so, however, the world at large has not caught up with this oversight just yet.  One reason for this may be that camera viewfinder ratios have themselves changed over the years.  Ansel Adams, for instance, used film that was 8″x10″ which naturally means that everything he captured would appear in an 8×10 print.  However, this is a large format camera ratio.  My favorite medium format (120mm film) camera, a Mamiya 645 tells you in it’s name that it’s ratio is 6:4.5.   35mm cameras and most SLR’s and DSLR’s use the 3:2 aspect ratio mentioned above.  An exception to this is some of the newer point and shoot camera’s actually have a ratio of 4:3, which still does not give you standard print sizes straight from the camera.

So what does that mean for my pictures?

The image above illustrates how an image is affected by cropping.  The red line indicates a 4×6 print size, the green a 5×7 and the blue an 8×10.  As you can see, an 8×10 cuts off quite a large portion of your print!  So why these sizes?

The grey area represents a standard 8.5″ x11″ piece of paper.

Many paper size standards and conventions have existed at different times and in different countries, but today there is one widespread international ISO standard (including A4, B3, C4, etc.), versus a localised standard used in North America (with: letter, legal, ledger, etc.). The paper sizes affect writing paper, stationery, cards, or some printed documents like photographs.  The standards also have related sizes for the envelopes used.  The ISO paper size A standard is based on each size being half of the size of the previous one, when folded parallel to the shorter lengths. This system allows for a variety of useful applications, such as the enlarging and reducing of images without any cutoff or margins, or folding to make a booklet of the next size down.

The mathematics behind this useful feature is that the sheets have an aspect ratio (that’s the ratio of the length to the width) of the square root of 2.

As a photographer, you try to shoot “fat”, meaning that you leave space to crop.  This is a challenge sometimes as your subjects are not always super cooperative so that you have time to think when capturing a picture.  Not into cropping?  Who can blame you?  Non standard print sizes still have a home on the wall.  Custom framers can cut a matte to fit around your image so that it will fit into a standard frame size, without sacrificing a large portion of your favorite photos.


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