The Rule of Thirds

I recently had a practical lesson regarding the "rule of thirds" as it applies to photographic composition. I had some pictures not turn out the way I wanted, and when I analyzed them, the "rule of thirds" is where I kept winding up.

Before I get going with this, and before anyone gets their hackles up by my calling it a "rule", understand that, like the Pirate Code, photographic rules are guidelines more than actual rules. They were made to be broken. But breaking compositional guidelines willy-nilly, with no regard for the consequences, can result in sub-standard images (like mine were!) If you choose to break a compositional guideline, at least know what you're doing, and know you're doing it on purpose.

The "rule" of thirds states that you should put your photographic subject not at the bulls-eye center of your frame, but at one of the 1/3 points of the frame. If you divide your frame like a tic-tac-toe board, your subject should be at one of the intersection points of the tic-tac-toe lines. Here's a quick example:

This is a photograph of a flower, with the flower bulls-eye in the center of the frame. It might work as an illustration in a botanical textbook, but as far as putting it on the wall, it's a little lacking:


By re-composing the photograph with the flower off closer to one corner, we can totally change the feel of the picture:


The choice of corner is not arbitrary by any stretch. What if we put this one in the lower-right corner instead?


To me it feels like the flower is being crushed by the tree behind it!

The same compositional rules hold with horizon lines. It's the rare photograph that can stand having the horizon line bisect the image straight across the middle. Most of the time it helps to put the horizon line on one of the 1/3 lines. But which way to go? Depending on the composition, one will work better than another. Placing the horizon line high emphasizes the foreground. Placing the horizon line low emphasizes the sky. Depending on the weather, it can add a sense of freedom to the picture, or it can add a sense of foreboding if the weather is dodgy.

It was a horizon line rather than a flower that was giving me grief in this case. The film 4x5 camera I built for doing kite aerial photography can point anywhere from straight up to straight down, and can face all the points of the compass. But since there's no viewfinder to look through, all the composition has to happen on the ground. Last weekend I went out shooting, and came back with an odd lack of horizon lines. It's not that they didn't fall on the 1/3 lines, they weren't typically in the frame at all!

Since I have a model of my KAP camera in CAD, it's to CAD that I turned for the answer. I know the size of my negative, I know the focal length of my lens, so I did a quick exercise to find my field of view. I was amazed to find how small it was!


The blue angles represent the actual field of view of the camera. But the red angles represent the 1/3 angles of the field of view. They're tiny!

What I learned from all this is that a down-angle of only 6.65 degrees is enough to put the horizon 1/3 of the way down from the top of the frame. It also means that the tolerance for the suspension to hold the camera off horizontal is extremely tight!

I've added some compositional guideline stickers to the camera, and will be adding a bubble level to the top of the Picavet before the next flight. I could probably do with a much wider angle lens on this camera. But since the camera was built around the lens, that would mean building a new one from scratch. For next time.

Tom