Hello

I have built a 6x17 camera and and would like to know how one would determine the lens to film plane distance for a hyperfocal setting for a particular lens for a couple of apetures, say f 16 and f 32. The lens is a Super angulon 90 F8. I was planning on having three settings for the lens, one focussed on infinity (the lens is used here most of the time), one hyperfocal at f 16 and one hyperfocal at f 32 (i need to start including some foreground interest in my photos, thus this requirement). Do you find the hyperfocal distance through trial and error by taking photos at various distanced subjects, focus settings and apetures, or is there some sort of mathematical way i can determine it. My usual way of focussing is ground glass viewing. Currently there are no focus setting marks on the camera i have built (but i realize i will have to do so if i want to change the focussing)

-- Phil Brammer (filsta@goconnect.net), February 03, 2002

Answers

The following formula is used to determine hyperfocal distance. Hyperfocal Distance (H) = F2C divided by 12f Focal Length of Lens x Focal Length of Lens or F2 f/Stop x Circle of Confusion fc

10x10x250 = 100x250 = 25000 divided by = 463 feet. 12x4.5 = 54 = 54 If the above lens (10) is focused at 463 feet and used at f/4.5 every thing from one-half of the focal distance (231 1/2 feet) to infinity will be acceptably sharp. (NAVPERS 10371) Pat

-- pat krentz (patwandakrentz@aol.com), February 03, 2002.

Phil,

Check out a program called fCalc at www.tangentsoft.net.

-- Scott Soper (scottsoper@earthlink.net), February 04, 2002.

The following website has just about any lens formula you could need:

http://WWW.graflex.org/lenses/lens-faq.html

-- Andy B. (buckwiet@yahoo.com), February 04, 2002.

You can use the formulas as a guide, but you should test the results. Depth-of-field doesn't have a sharp boundary. Also, the formulas are based upon assumptions about how critically the prints will be viewed, e.g., typically that prints will be viewed from a distance equal to their diagonal. If you examine a large print from a close distance, the depth-of-field will be smaller, corresponding to needing a greater hyperfocal distance.

-- Michael Briggs (MichaelBriggs@earthlink.net), February 04, 2002.