Understanding aperture and lens diffraction - Weekend

Understanding aperture and lens diffraction

Albert PedrosaAlbert Pedrosa
Photo Mania

A FEW weeks ago, I read an article from Steve Perry that talks about lens diffraction. In an instant, I got hooked with the article, having heard the terminology before but didn’t seem to make sense during those times.

After a juicy read, I felt like a newbie photographer again hungry for learning. No matter how many times I tell my students that there cannot be an end in learning photography regardless of what level of expertise you are in, I’m still at awe every time I learn new stuff.

I’m no landscape photographer, although you can’t stop me from taking a beautiful scene when it’s in front of me. I know that there’s so much to learn from different genres of photography and it can get really deep the moment you start spending time understanding the different elements of an image.

I was quite ashamed of myself when the topic in the article tried to explain that depth of field, which is controlled by aperture, does not equate to image sharpness. I have to admit, I thought that the higher the value of aperture would mean sharper results. Nope. If you think the same, we’re in the same boat.

BUKIDNON. This photo was taken with smaller opening at f22 to extend the depth of field up to the mountains in the background. This time, DOF is more important than sharpness of the foreground.
BUKIDNON. This photo was taken with smaller opening at f22 to extend the depth of field up to the mountains in the background. This time, DOF is more important than sharpness of the foreground.

Although the higher the aperture value means your focus will go farther than the subject, it doesn’t mean that the subject will be at its sharpest. And surprisingly, the higher the aperture value, the lesser the level of sharpness you get from your subject. Does that get your attention now?

Lens diffraction happens when the light is choked by the aperture or opening. The smaller the opening or higher aperture value, light is forced to go through a small hole that gives you a farther depth of field but sharpness suffers as well. The light tends to lose details when you force it through some tight angles.

A wider opening on the other end offers less light acrobatic stunt. The light goes through the aperture without so much bending but limits the depth of field in return. They say that the best and sharpest aperture of any lens is two stops from the widest aperture of the lens. If your lens widest aperture is 1.4, then the sharpest will be at 2.8.

If you want details especially when shooting product or even landscape, dialing up the aperture will ensure a farther focused field but not sharper details. Before you make the most of your aperture, you should ask yourself first if you need the greater depth of field over sharpness of your subject.

Try it yourself and find out at what aperture your lens will give you the sharpest. Keep on shooting, everyone!

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