[Tonytee]

I have a Pentax-A 50mm f/1.7 lens. Awesome piece of equipment. I would like to know what the green A on the aperture means. Does it mean to set it on A and then forget the other f/stops because it is automatic? Thanks for any assistance offered.

tt

[Sandy Hancock]

I have a Pentax-A 50mm f/1.7 lens. Awesome piece of equipment. I would like to know what the green A on the aperture means. Does it mean to set it on A and then forget the other f/stops because it is automatic? Thanks for any assistance offered.

A is for automatic. With a modern digital camera you can change the aperture using the control wheels, and with later film cameras you can use shutter priority and program modes which allow the camera to set the aperture automatically for correct exposure.

[dms]

About depth of field (DOF) for older lenses--my "Leica Manual" book from 1953 has as basis 8"x10" print hand held at a normal viewing distance--so it is same as currently used, or as I recall it. And I have a British mountaineering photo book from (I believe) 1944 and I recall it is the same/consistent.

Actually it doesn't matter if the basis is different--so long as you evaluate and adjust the model if need be. It is a model (the DOF markings/tables) that allows one to work quickly and surely. On the other hand to not use a model means you are guessing. And having the model already (implemented) on the lens is very convenient. If you use it and find the DOF is too small or too large (e.g., because you print/view much larger or smaller) then you adjust by using DOF markings (table entry) for 1 or 2 stops more or less open.