Focus on Infinity

“Infinity: unlimited extent of time, space, or quantity : boundlessness”, according to Merriam Webster. A difficult concept under any circumstances, infinity in photography can be an even more elusive state. In photography, the definition of infinity includes “A distance between a subject and the camera so great that rays of light reflected from the subject may be regarded as parallel.”, and “A distance setting of the camera lens beyond which everything is in focus.”.

Fresh Snow on the Sangre de Cristo

Recent travails in shooting distant landscapes has me studying the issue in more depth, and today was the day for some cursory field testing. The plan was to conduct a scientific experiment to determine if the auto focus mechanism on my Canon 70D with my 70-200 lens was handling infinity properly. Today was supposed to start with a beautiful clear morning, following days of snow and fog and I was glad to finally be able to get out and do some shooting with Big Dog.

As usual though, my experiment didn’t turn out to be all that scientific or even informative, but I had fun and got some good usable shots 🙂 What I did find out though was gratifying in that I believe that my lens is performing exactly as it should. My method was to take two shots of every scene, one with the auto focus and the second identical shot with the lens set to manual and the focus set to or near the “infinity” mark focused on the distant Sangre de Cristo mountain range as sharply as possible. Then, in front of Photoshop a 100% view of the two images side by side was going to tell me which method is better. I had recently watched another photographer on Youtube who claimed that manual mode focused on infinity was the way to go.

Now the really confusing part of the experiment is that many professional lenses have the capability to focus “beyond infinity”… where nothing is actually in focus. Apparently the equipment can compensate for micro expansion and contraction of the metal due to temperature changes and may require that space slightly beyond the infinity line for that purpose.

Fox with Prey

It was indeed a beautiful morning and we were awarded a couple of bonus shots for our effort 🙂 Along the way I spotted both a fox hunting and then later a coyote hunting in the beautiful fresh snow. The fox was already heading for home with a tasty morsel in his mouth and the coyote was still hunting but paused to cast a wary glance in our direction.

Coyote in Fresh Snow

Coyote in Fresh Snow

The mountains were magnificent as usual and the clear day was perfect for my little test. My scene is perfect with some nearby pine forest covered foothills backed up by the distant peaks of the Sangre. As I conducted my tests I noticed some curious behavior exhibited by the equipment. When focusing on the nearby mountains the camera on auto focus chose to focus exactly on the infinity mark, while the distant mountains resulted in a focus slightly beyond the infinity mark. I thought I was onto something there, a possible malfunction in the auto focus mechanism perhaps. But the follow up shots using manual focus proved the auto focus to be exactly correct based on what I was focusing on.

These findings were very good news for confidence my equipment, but also raised a new question that I have no definitive answer for. Why are the close mountains which are at infinity focused differently than the distant mountains which are also beyond infinity. I guess the simple answer to that is that the close mountains are at a sufficiently varied distance and angle to result in a slightly different infinity value from the vastly distant Sangre de Cristo range more than 60 miles away. In any case, the idea of just setting the camera to the infinity mark is out of the question, at least for a 200mm lens. This practice would probably work fine for a wide angle lens where the infinity point is only a few feet from the camera. Each scene is going to require evaluation to determine what exactly is the most important feature to render the most sharp in the image. If the entire image needs to be sharp, focus stacking in Photoshop might be required.

All in all, the day was a success, important knowledge acquired, some nice images to work with collected, and now in the last couple of hours some more great shots of the little fox family that I found the other day 🙂 Please be sure to visit my image website to see all the new pictures that have been made for sale as wall art, cool household items and royalty free stock!

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