[Leica] Forget about depth of field scales

[Mitch Alland <malland@mac.com>]

Whenever I take a landscape photograph in which I want maximum DOF, I start wondering where to focus. Often, I have focused on the hyperfocal distance and the results were not as sharp as I would have wished. Recently, I posted a question on the LUG concerning this matter and received a response stating that one should focus on the hyperfocal distance of two f-stops larger than the aperture one is using. Indeed, this halves the circle of confusion from 1/30 mm to 1/60 mm by pushing the plane of focus out further. However, after reading a series of four interesting articles published in Shutterbug by Harold Merklinger, I see that for MOST landscape photographs with, say, a 35mm lens one would effectively get the greatest range of sharpness by focusing on infinity. [Unfortunately I don't remember the website where I found the articles but you can do a Google search.]

Basically, Merklinger states that the DOF scales found on lenses were developed by Leitz in the 1930s, based on the quality of lenses and films then available which could resolve 1/30 mm. With modern films and lenses, forget this, he says. He concludes that, for all lenses, no matter which focal length, you should simply focus on infinity if the "smallest object to be recorded is bigger than the (stopped-down) lens aperture." If he is right, for a 35mm lens at f5.6-f/11, this I likely to be the case for most general landscape photos, and one can just focus at infinity. Do you agree with this?

For the other cases, in which the smallest object to be recorded is smaller than the lens aperture, he gives a simple formula to calcute the DOF. (Size of object/lens aperature size x focal distance gives 1/2 the DOF).

Always wanting to simplify things, my inclination is to:

1. use the infinity focus for general landscapes in which you want things far away to be sharp; 

2. focus on the main object if there is one; and 

3. use hyperfocal distance of two f-stops larger than the aperture one is using in cases in which you want maximum DOF in landacapes where the main is somewhat in the foreground, say 20 feet away. What do you think of this?

Mitch