How to calculate wide end of zoom focus (Angenieux 16-42mm)

[Tom S]

It appears that on my Angenieux 16-42mm the focus at the 16mm end at about 6 feet and further is infinity. Anything from the mid 20's to 42mm focus is according to the focus scale. I assume this is a normal phenomenon because of the physics of a wide lens. Are there charts to help find out at what focal length infinity begins?

 

[Bastian Meier]

I guess you are talking about the Depth of Field. (DOF)
DOF Depands on different factors. The Focal length, the aperture, the distance of focus, and the sensor size.

The bigger the focal length, the smaller the the DOF.
higher aperture (smaller opening) means bigger DOF.
the further away the focus is from the Lens, the bigger the DOF is.
bigger sensor means smaller DOF.

Of course all this can exactly be calculated.

There is also the term of hyperfocal, which means that at the given focal length, aperture, from a certain distance on everything is in focus till infinity.