I know it is difficult to incorporate depth-of-field scales in modern zooms but even on modern prime lenses (like my Nikon f1.4 50 mm) they are rudimentary to the point of uselessness). And I miss them. One of the great advantages of a proper depth-of field-scale is the rapid setting of the hyperfocal distance without having to remember what the hyperfocal distance is. All you have to do — and it seems that very few photographers know this — is decide what the near point of acceptable focus is (by focusing on that point and reading the focus scale), swing the focus ring so that the ∞ mark lines up with a particular aperture (e.g. f/8) on the depth-of-field scale, then look at the other side of the scale to see if at that aperture the near point shown on the focus ring is within the range of acceptable focus. If it is, then set that aperture for exposure. If it is not then move the ∞ mark to larger aperture number (i.e. smaller stop, e.g. f/11) and try again until the near point is within the range. The whole process is so rapid that it is easier to do than describe.
|Same as above, this time using f/11|
Now, the interesting point is that you will not get the same result using a modern depth-of-field calculator for a full-frame 35 mm lens. Instead of 12’ to ∞ at f/8 we get 17’ to ∞, and instead of 8’ to ∞ at f/11 we see 12’ to ∞ on a calculator. The explanation is simple. The depth-of-field scale markings on an individual lens depend on the value taken for the circle of confusion used by different manufacturers at different times. For the Pancolar made by Carl Zeiss Jena in the 1960s shown in the illustrations above, the circle of confusion was taken as 1/20 mm (i.e. 0.05 mm). This is what Werner Wurst had to say in the 9th edition of his Exakta Manual (2nd English edition, 1966):
...a circle of confusion of 1/20 mm is still recognized as sharp for the 24 x 36 mm format. The tolerances of unsharpness in which the depth of field scales of the EXAKTA Varex lenses made in Jena and Görlitz are based are derived from these data. However, other optical manufacturers reject as unsharp anything larger than 1/25 mm [0.04 mm]. In actual practice these variations can be ignored; however, bigger variations in either direction can no longer be tolerated. Thus, the assumption of a still smaller circle of confusion (e.g. 1/30 mm [0.03 mm] would unduly restrict our possibilities during focusing while larger diameters (e.g. 1/10 mm [0.1 mm] will be immediately be recognised as unsharpness.