Sunday, November 25, 2012

Understanding Depth of Field in Photography

Understanding Depth of Field in Photography, article.

It's just the rudiments, but it's illustrated and seems pretty clear.


Andreas Weber said...

Could use some proofreading by someone who really understands the topic ...

The very first sentence(!): "Depth of Field (DOF) is the front-to-back zone of a photograph in which the image is razor sharp. As soon as an object (person, thing) falls out of this range, it begins to lose focus at an accelerating degree the farther out of the zone it falls ..."
Actually, DOF is the range of "acceptable blur". The image goes out of focus as soon as you leave the plane of focus, blur increasing with the distance from that plane.

"The aperture is the opening at the rear of the lens ..."
While there are lenses with the aperture behind the optics it's rather rare today. In many common designs you want to have the aperture in the center (to avoid distortion).

Explanation of "f-stops" is somewhat iffy, but not really wrong.

But in #5 the explanation seems to contradict itself within two sentences: "To maintain the compositional integrity of the shot, but still have the change in DOF from a distance, you can change the focal length (either by changing lenses or zooming in). Why does changing the focal length negate the effects on DOF?"
The second sentence is approximately correct. If you change distance and focal length to keep reproduction ratio constant you won't see a lot of change in DOF. (Doesn't work when approaching infinity, but you won't change the distance to a landscape to change its size, either...)

And frankly I just don't care much for the entire explanation. If you can't explain such a simple concept in a simple and correct fashion ...

Eolake Stobblehouse said...

Fair enough, it's not so precise, and I don't know where "rear of the lens" came from.
I only skimmed it, since I read books about this long ago.

But if you know of a better introduction article, I'd love to know it.
Wikipedia articles tend to grow too long and complex.

Ken said...

The easiest explanation would be to show the light rays from slightly out of focus objects as they pass through a lens and then form the image, and how that changes as the aperture changes.