rehess wrote:
I thought it might be helpful to look at real lenses. Posted below is a picture of two Super Takumar M42-mount lenses. The lens on the left has a focal length of 35mm and the lens on the right has a focal length of 50mm.
The numbers closest to the mount {bottom of the image} are the aperture ring.
The next set of numbers
16-8-4-^-4-8-16
are indicators for the distance scale above.
The red indicator mark shows the distance we are focusing at, while the {aperture} numbers on the right show the closest distance in the DOF, and those on the left show the furthest distance in the DOF.
In this case, I set each lens so that infinity is the furthest distance for F/8 {infinity mark is above "8" on the left side of the indicators.
For the 35mm lens, I am focusing at 15', and everything between 8' and infinity will be in the DOF.
For the 50mm lens, I am focusing at 30', and everything between 15' and infinity will be in the DOF.
added: these numbers make an exercise like this much easier, but they didn't last much beyond the advent of auto focus.
I thought it might be helpful to look at real lens... (
show quote)