Focusing the View Camera: A Scientific Way to Focus the View Camera and Estimate Depth of Field. by Harold M. Merklinger. Merklinger’s method is less widely used, but is much easier to apply in the field. . Harold Merklinger describes his method for optimizing depth of field here. Harold Merklinger on Depth of Field. If you arrived at this page by a direct link, it will be helpful for background information if you read my article, More on Depth.
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Be aware that if you specify the focal length in millimetres, the hyperfocal distance will also be in millimetres. There are similar expressions for working out the nearest and furthest points of focus, but I’m not going to give them, as they are well-known — just do a Web search for ‘depth of field formulae.
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So far merklinyer this article is concerned, his method for dealing with scenes that extend to infinity or, at least, for miles can be expressed very simply: Merklinger’s method for scenes with distant objects. The use of hyerfocal distance has the benefit of long usage, and is well-understood.
Merklinger’s method is less widely used, but is much easier to apply in the field. In this article I’ve assumed a basic familiarity with photographic concepts such as aperture, exposure, and focus.
I haven’t presented any of the mathematical analysis, only the results, because the math is well-established and easy to find elsewhere on the Web. The problem stated The problem, in essence, is to find camera settings — lens selection, aperture, etc.
To have objects sharp over a wide distance range is often desirable in landscape photography, because subjects close to the camera give a sense of depth and scale to the image, which might be lacking if the whole scene is distant.
The diagram below shows a typical situation, and one that will be used to illustrate the rest of this article. The classic depth-of-field problem in landscape photography: Hyperfocal distance as it is traditionally employed in landscape photography — focusing at the hyperfocal distance ensures a depth-of-field from half the hyperfocal distance to infinity.
Merklinger’s aperture for a disk of confusion of 5mm-6mm, for various lens focal lengths.
Technical Books on Photography by Harold M. Merklinger
With this aperture, and the lens focused at infinity, then features 5mm or larger will be distinguishable. The nearest point of acceptable focus according to the conventional depth-of-field formula is shown for comparison. Merklinger’s aperture for a disk of confusion of 2mm-4mm, for various lens focal lengths.
With this aperture, and the lens focused at infinity, then features 2mm or so or larger will be distinguishable. This graph shows how the point of nearest focus varies with apperture, when focused at the hyperfocal distance, for various lens focal lengths. However, the 18mm lens should be barold from about 5m to infinity for any aperture setting.
It’s hard to take an out-of-focus landscape shot with lens if you set the focus manually to something reasonably close to the hyperfocal distance which, of course, varies with aperture. For all other lenses, more care is required. The hyperfocal distance with this configuration is The crucial point here is how rapidly the far point collapses if the lens is focused too close: How the near point varies with the chosen disk of confusion in Merklinger’s method.
This graph is for a 27mm lens and, although the gradient of merkklinger line is different for other lenses, it is always a straight line.
For more wide-angle lenses, the near point is even closer.