Hyperfocal distance

[twm47099]

The use of hyperfocal distance, while generally used, has been somewhat controversial. The link below leads to some articles by Harold Mercklinger. His basic point is that using Hyperfocal distance guarantees that key features will appear soft, (being at the extremes of DOF).

http://www.trenholm.org/hmmerk/DOFR.html

His method for landscapes is to focus at infinity (so that will be sharp) and set the actual physical aperture at or below the diameter of the smallest near feature to be resolved. (f-number = FL/diameter of smallest feature) For example if the minimum size of near objects to be resolved was 1/4-inch (6mm) and you were using a 50mm lens, the f-number to be set would be f/11. (50mm/6mm) = 8.333 so go to the next f-number (f/11). While this seems to work (or at least be practical) for wide to normal FL lenses, but would result in diffraction for long lenses. 100mm is probably a limit where diffraction could cause softness (FL=100, dia = 6mm --> f/16.7 or f/22)

tom

[Dr. Harout]

...For example if the minimum size of near objects to be resolved was 1/4-inch (6mm) and you were using a 50mm lens...

tom

Tom, how much near? I'm confused, should it be "nearest object within the DoF limits"?
And welcome to the forum.

[twm47099]

...For example if the minimum size of near objects to be resolved was 1/4-inch (6mm) and you were using a 50mm lens...

tom

Tom, how much near? I'm confused, should it be "nearest object within the DoF limits"?
And welcome to the forum.

Dr,
Thank you for the welcome, I have lurked here for a few years and have learned a lot.

Merklinger does not place a limit on the foreground distance. It is not very intuitive, particularly if you are used to the concept of DOF. I quote one of his examples below (the link above has the theory and example with a photo, that may be easier to follow). He says:

"Let me illustrate with an example. Figure 3 shows a photograph of the Newfoundland village of Placentia. In the foreground are a cannon, some grass, some gravel, and some trees. The picture was taken with a 90 mm lens on a Leitz-Minolta CL at f/8. The aperture is thus about 11 mm in diameter. The hyperfocal distance for a 90 mm lens at f/8 is 106 feet. The cannon is at a distance of about 30 feet, and the distance to the village is about a mile: 5280 feet. Had I focused at the hyperfocal distance, the resolution spot size at the cannon would have been 8 mm and at the village it would have been 0.55 meters or about 21.5 in. If, on the other hand, I focus at infinity, the spot size is 11 mm at the cannon and 11 mm at the village. Or 11 mm anywhere else, for that matter. True, diffraction effects won't let me resolve 11 mm at 5000 ft., but at least resolution at the village will be as sharp as nature permits. The change in spot size from 8 mm to 11 mm at the cannon would be almost impossible to detect in the image. The foreground is admittedly not tack-sharp. But I can recognize the cannon, the gravel, the grass and the trees. Had I focused at the hyperfocal distance the telephone poles in the village would have been almost erased, and windows in buildings would have been just blurs." and

"The general rule for scenic photographs, where one wishes to maximize the depth of field, is as follows. Set the focus at the distance of the most distant object. Then set the lens opening to the size of the smallest object to be resolved in the foreground. No calculations needed!"

The photo in the article measures only 4-inches by 5-inches on my monitor, but the details on the canon (and gravel) as well as the distant village, appear sharp. I've never actually tried his method, but now that I've got my A700 and the weather is finally getting better, I intend to try.

He has some other interesting articles that can be found on the main page:

http://www.trenholm.org/hmmerk/

There used to be a lively debate on his views vs DOF on www.photo.net in the medium format forum with example photographs supporting both sides position.

tom

[Dr. Harout]

Thanks for the link. Great to have you with us.

[Birma]

The use of hyperfocal distance, while generally used, has been somewhat controversial. The link below leads to some articles by Harold Mercklinger. His basic point is that using Hyperfocal distance guarantees that key features will appear soft, (being at the extremes of DOF).

http://www.trenholm.org/hmmerk/DOFR.html

Hi Tom - very interesting link. Welcome to the forum from me as well