On 08/25/2018 06:06 PM, nospam wrote:
In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with lens
focal length, not field of view of the subject.

actually, it's aperture.

actually, it's the ratio of focal length to aperture.

nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes, and
in some cases (usually movies), t/stops are used, which is actual light
transmission through the lens, not a simple ratio.


For an ideal optical system, the depth of _focus_ (on the image side) is
a function only of wavelength and numerical aperture, i.e. the sine of
the half-angle of the cone defined by the rim rays (i.e. the illuminated
cone). That's where wave properties come in.

On the object side, the depth of _field_ equals the depth of focus
scaled by the square of the magnification. Magnification is of course
the ratio of the object distance to the image distance.

Aberrated optical systems degrade a bit more slowly because they're not
as good to begin with.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com