[Leica] Hyperfocal distance

[lrzeitlin at optonline.net (Lawrence Zeitlin)]

Here is a question for LUG technical experts.

I was checking through my 1948 edition of the Graphic/Graflex manual  
and I found a rule of thumb for computing hyperfocal distance. The  
rule states that the hyperfocal distance of any lens is equal to the  
effective diameter of the lens opening x 1000. (H=d x 1000)

Example: A 50 mm fl lens at f4 has an effective aperture diameter of  
12.5 mm. The hyperfocal distance is thus 12500 mm (12.5 meters or 41  
feet). At f8 the lens has an effective aperture diameter of 6.25 mm  
so the hyperfocal distance is 6250 mm (6.25 meters or 20.5 feet. I  
checked the formula calculation against Kodaks chart of hyperfocal  
distance for various focal length lenses and apertures and the  
figures seem to correspond closely.

The lenses referred to the the Graphic/Graflex manual and the Kodak  
tables were all normal prime lenses. None were retrofocus designs.  
Further the Kodak tables, and I assume the Graphic/Graflex formula  
used a circle of confusion equivalent to 2 minutes of arc, roughly  
1/1720 of the focal length. That works out to about .03 mm for a 50  
mm lens, about a resolution of 34 lines per mm. I recall that this  
was the resolution that the late great Modern Photography deemed  
acceptable (but not great). Doubling the calculated resolution to 64  
lines per mm by increasing the multiplier in the equation to 2000  
should bring the formula more in line with the demands of LUG listees.

Now my specific questions. Is the formula still valid for modern  
retrofocus lenses as used in most DSLRs and the M8? Does anyone still  
use hyperfocal distances nowadays? I confess that I make a stab at it  
in shooting my Rollei 35. An estimate of hyperfocal distance is also  
useful in street photography when you can't take time to focus. But  
do the estimates work for modern optic designs?

If you can get your hands on it, the old Graphic/Graflex manual is  
quite a read. The chapter on lenses was written by Rudolph Kingslake,  
the chapter on printing by Ansel Adams, that on composition by  
Berenice Abbott, and so on. War photos were of WW2. News photos by  
WeeGee. The section on PR photography was illustrated with photos of  
young actors and actresses who have become household names. Cameras  
weighed five pounds and up. Heiland flash guns mounted four  
flashbulbs in case a lot of light was needed for slow color films at  
ASA 12.

Thank God for relatively tiny Leicas.

Larry Z