Why don’t more cameras show depth-of-field or hyperfocal information?
Asked 2/4/2014
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Cameras know the focal length, aperture, and focused distance, so it seems like they could calculate and display depth of field or even hyperfocal distance in-camera. Since many modern lenses also lack printed distance or hyperfocal scales, why don’t more cameras provide this information in the viewfinder or on the screen?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
6
First, a word about what depth-of-field is and is not:
In a way, depth-of-field is an illusion. There is only one plane of focus. Everything in front of or behind the point of focus is out of focus to one degree or another. What we call DoF is the area where things look, to our eys, like they are in focus. This is based on the ability of the human eye to resolve certain minute differences at a particular distance. If the slightly out-of-focus blur is smaller than our eye's capability to resolve the detail then it appears to be in focus. When you magnify a portion of an image by making it larger or moving closer to it you allow your eye to see details that before were too close together to be seen by your eyes as separate pieces of the image.
Since things are gradually blurrier the further they are from the point of focus, as you gradually magnify the image the perceived depth of field gets narrower as the near and far points where your eyes can resolve fine details moves closer to the focus plane.
Since depth-of-field is dependent upon viewing size and distance as well as the visual acuity of the viewer it is hard for a camera to indicate depth-of-field if it doesn't know what the display size of the photo will be. Assuming the standard 8x10 viewed at 10 inches by a person with 20/20 vision is probably a little too broad. Because of this it has never been a priority to the users and designers who advise major manufacturers on what features are desired in upcoming models. Most of the photographers in those groups are advanced enough to have a feel for the distances/focal length/apertures they use the most and probably don't see a need for it. They also understand how to use distance scales on lenses that are marked well enough to be usable. Unfortunately, lenses with usable distance and DoF markings seem to be getting more and more uncommon. This seems to indicate the market in general doesn't demand such a feature.
Although it is not in-camera, these tools from DepthOfField master.com are simple, easy to use, and the price is right (free).
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
12y ago
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Some cameras do show a depth-of-field scale, but many don’t because depth of field is not a single exact value. Only one plane is truly in focus; the “depth of field” is the range that appears acceptably sharp, and that depends on assumptions about viewing size, viewing distance, and eyesight. Traditional DOF tables use a standard circle of confusion based on a typical print size and viewing distance, but those assumptions may not match how an image is actually viewed today.
That makes any in-camera DOF display somewhat approximate unless the camera also knows your intended output and viewing conditions. A hyperfocal readout has the same limitation because it is based on the same assumptions.
Also, when composing, many cameras offer a practical alternative: a depth-of-field preview button that stops the lens down so you can directly judge the scene. On some mirrorless cameras, especially with EVFs, a focus-distance scale and approximate DOF bar can be shown during manual focus.
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