Re: Distribution of DoF

On 22 Apr., 22:04, d...@xxxxxxxxx (Dave Martindale) wrote:
Monica Schulz <monica.sch...@xxxxxxx> writes:
The depth of field is exactly it. As I understand the case dof and
depth of focus are related in the following way: The depth of focus
covers some fraction of the focal length and the depth of field covers
that same fraction of the object distance.

That's not true in general. Without sitting down and working out the
math, it's probably *exactly* true only at 1:1 - where the image size
and object size are the same, and the light cone angle is the same in

<snip>
There's a very nonlinear relationship between the distance to an object
in object space and the distance to the plane of best focus in image
space. Someone else further down the thread has given one form of the
"lens equation" that is used to calculate this. You'll find that in
normal photography, with the image considerably smaller than the
subject, that the DOF is quite asymmetric - it extends considerably
further on the far side of the plane of best focus in object space than
it extends on the near side of that plane.

So tthe asymetricity is beeing applied by the lens equation?!
As school is long time ago for me and math has never been my
favourite, can you please tell me how the lens equation is beeing
solved for the image distance?

Thanks for the hint I have so obviously overlooked in the other post!
Monica


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