A couple of weeks back I was testing my lenses for front/back focus, and an idea struck me: it's entirely possible to setup the camera to constantly back or front focus, so to permanently change the one third/two third (theoretical) ratio between front and back focus.

Not asking about personal opinion on the thing, question is pretty simple and straightforward: is there some known example of peoples doing this? Maybe some well known photographer famous for a set of shots related to front/back focusing?

  • \$\begingroup\$ Huh? What's a "front/back" focus? You need to define the terms you use. \$\endgroup\$ May 10, 2016 at 17:19

1 Answer 1


The ratio of the amount of Depth of Field (DoF) in front of the focus distance to the amount of DoF behind the point of focus is highly variable. At Minimum Focus Distance (MFD) most lenses give a DoF that very closely approaches 1:1 or 50/50. At any focus distance past the hyperfocal distance the DoF ratio is 1:∞.

The common 1:2 or 33/67 rule of thumb is based on medium focus distances and apertures and will vary from lens to lens based on focal length, aperture, and sensor size. Assuming the image will be displayed at 8x10 inches and viewed from a distance of 10 inches by a person with 20/20 vision, a typical 50mm lens on a 35mm sized FF camera set at f/5.6 only distributes the DOF in the 1:2 ratio at a focus distance of 17 feet. If the focus distance is shorter the DoF is more evenly distributed front-to-rear. If the focus distance is longer the DoF will be even more heavily weighted to the rear. If we change the aperture of our 50mm lens on the 35mm camera above to f/1.4, the focus distance that gives a 1:2 ratio is 65 feet! If the aperture is set at f/16, the 1:2 ratio occurs at a 6 foot focus distance.

Keep in mind that there is only one focus distance - everything in front of and behind the point of focus is blurred to one degree or another. What we call DoF is the area which appears to be in focus because the amount of blur is smaller than our eyes ability to distinguish it from a sharply focused point.

In fact, what you describe in your question is pretty much what any photographer does when they calculate the hyperfocal distance for a lens, aperture, camera, and display size. By focusing on the nearest point that allows everything behind that point all the way to infinity to be acceptably sharp, as well as allows everything from the point of focus to half that distance from the camera to also be acceptably sharp a photographer is leveraging the uneven distribution of DoF in front of and behind the point of focus to their advantage.

Since this is such a well known and often used technique, it would be hard to say any photographer in particular is famous or well known simply because they used this technique. There have been many well known photographers who used the technique. Pretty much every landscape photographer, famous or not, has used it.

Even apart from calculating the hyperfocal distance there are common techniques that fudge the point of focus a little to place the nearest and most distant points in a scene within the DoF. Product photography, for example, often uses such a practice to try and make a box viewed at an angle appear to be in focus from one end to the other. Since the use of such methods are widespread and common, it is hard to say that anyone in particular is well known for using them. There are certainly well known photographers who do it, but that's not the primary reason the are well known.

Finally, 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 eyes, 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. Any in-camera DoF measurement is going to be based upon an assumption regarding the eventual viewing conditions of the photograph.

Assuming the standard 8x10 viewed at 10 inches by a person with 20/20 vision is probably a little too broad in the current digital environment. But most of the online calculators still assume this standard viewing size and distance. If you expect to view images at a 1:1 pixel size on a computer monitor, the DoF for the same exact image will be much narrower. After all, viewing a 22MP or so image on a monitor with 96ppi pitch is like viewing a part of a 60x40 inch print!


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