


Can someone please explainpreferably not using the confusing language of many booksexactly what the definition of hyperfocal distance is?

For every aperture with a given lens, there is a hyperfocal distance. This is defined as the closest distance you can focus on, and still have the background (infinity) reasonably sharp.
Many photographers don't agree with the standards for "reasonable", and use different distances.
 Ole Tjugen, Luddite Elitist
Norway

Originally Posted by Ole
For every aperture with a given lens, there is a hyperfocal distance. This is defined as the closest distance you can focus on, and still have the background (infinity) reasonably sharp.
I'm nitpicking (occupational hazard!) but I think it's "for every aperture for a given focal length and film format..."
The hyperfocal distance for an aperture with a zoom lens will change as you alter the focal length. Also a 50mm at f2.8 will have a different hyperfocal distance in 35mm format than with 6x4.5, 6x6, etc.
Forgive me for stating what may have been the "bleedin' obvious"! :)
Regards,
Frank
...A child's middle name is so he can tell when he's REALLY in trouble.

Yes, hyperfocal distance is a characteristic of lens focal length and aperture. Typically hyperfocal distance manifests itself in the manner that at the point of true focus one third of the hyperfocal distance is in front of the point of true focus and 2/3 of the distance is to the rear of the point of true focus.

"When a lens is focused at infinity, the closest distance that is still in focus for any given f/stop is called the "hyperfocal distance". The practical value of this measurement lies in the fact that if the lens is focused on the hyperfocal distance, everything from *half* that distance to infinity will be in focus.
When used as a focusing point, the hyperfocal distance provides the greatest possible depth of field that can be obtained with a given lens at a specific aperture."
 The Enctclopedia of Photography  Vol 10. p. 1793
Some lenses, I'm looking at a Hasselbald Sonnar 150 mm right now, have a scale on either side of the focusing index marked with f/stops to indicate the limits of "acceptabe focus" when focused at any given distance. As an example, with this lens, at f/22 and a primary focus of 25 meters, everything between 13 meters and infinity will be "acceptably in focus"; at f22 and a primary focus of 5 meters, everything from 3.8 meters to 8 meters will be "acceptably in focus".
There are mathematical formulas to figure this out  but I'm trying to keep it simple.
Carpe erratum!!
Ed Sukach, FFP.

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I just remembered, if you happen to have a palmtop that runs Palm OS, there's a handy little shareware program called fcalc that will tell you the hyperfocal distance for a given film size, focal length and aperture.
It also does upteen other things like depth of field calculations and angle of view. It should be available somewhere on www.tangentsoft.net

Andrew,
since you're in the 35mm forum, I'm supposing you might actually be planning to use the depth of field scales on your lens to determine hyperfocal settings at a given aperture. Be aware that the lens DOF engravings are very optimistic, i.e., assume a small final print. to make a satisfactory 6x9 inch print from 35mm you should be shooting 2 stops smaller then the DOF scales indicate. For example if you shoot at f8 set your hyperfocal distance using the f4 mark on the lens to obtain a reasonably sharp print.
take care,
Tom

Originally Posted by Ole
Many photographers don't agree with the standards for "reasonable", and use different distances.
The Problem is that "reasonable" depends on:
 the enlargemnt factor
 the viewing distance

Originally Posted by Tom Duffy
Andrew,
Be aware that the lens DOF engravings are very optimistic, i.e., assume a small final print. to make a satisfactory 6x9 inch print from 35mm you should be shooting 2 stops smaller then the DOF scales indicate. For example if you shoot at f8 set your hyperfocal distance using the f4 mark on the lens to obtain a reasonably sharp print.
The calculation of a "hyperfocal distance" is a theoretical one ... and one of the most important factors in its calcualtion is called the "circle of confusion". The "resolution" of any optical sytem is a measurement of the smallest distance separating two points  where the points remain recognizable as two points, and do not blur into one. It is properly given as an angle: the resolution of a telescope is usually given as 1/4 second or something like that. To simplify (?  debateable) things, we generally speak of camera lens resolution in terms of "lines per millimeter"  and this brings back memeories of the "Air Force Resolution Target" of 1951 (not certain of the year) and hours of peering through a microscope at aerial images on an optical bench. The "circle of confusion" was simply the "resolution at the film plane" given as the diameter of a circle  and most lens manufacturers have accepted an arbitray value based the Zeiss formula of [ Diagonal of Format / 1760 ] (am I remembering correctly?).
Remember  that is a theoretical value, and the actual resolution is not considered. It may be that a lens that cannot resolve a whole lot of "lines per millimeter" will not be "accepatbly sharp" to the ( *subjective* ) eyes of individual photographer, therefore he may chose to use a smaller aperture to try to obtain a greater depth of field than that indcated by the "hyperfocal scale" on the lens.
Theory is good  but it is never an adequate substitute for experience.
Carpe erratum!!
Ed Sukach, FFP.

I don't know the exact address, but google search "shuttercity". They have an automated depth of field calculator that gives depth of field and hyperfocal distance for any lens length at every Fstop on any format up to 11x14 I think. It also allows you to enter in focus distances and then will list every Fstop with its depth of field for every format. Of course every lens mfg will probably vary slightly but it will get you into the ball park. It provides a table that when printed provides an easy reference for the field.

