DOF dumb I guess!

[dewmuw]

Is this a dumb question? I know that altering the aperture affects the DOF - but why? What is the technical reason for it?

[dtrayers]

http://luminous-landscape.com/tutorials/understanding-series/dof.shtml

[dewmuw]

dtrayers wrote:
http://luminous-landscape.com/tutorials/understanding-series/dof.shtml

WOW! Great link - thanks.

[PacAce]

dewmuw wrote:
dtrayers wrote:
http://luminous-landscape.com/tutorials/understanding-series/dof.shtml

WOW! Great link - thanks.

But you still don't have the answer to your first question of why aperture affects DOF, do you? Which, btw, is a very good question, the answer to which I wouldn't mind knowing myself?

[dtrayers]

Ready for some math?

http://www.photo.net/learn/optics/lensTutorial

[stopbath]

The reason for depth of field being affected by aperture is due to the narrowing of the angle of usage of the glass.

When your lens is full open, you are using almost all the glass with all of it's curvatures. As you stop down, you sort of start dropping off the edges. The light path becomes straighter (goes through less curvature in the lenses). Eventually if you got to a pinhole aperture you would achieve perfect depth of field. You would have a pinhole camera.

Pinhole cameras require no lens (image is not sharp, but hyperfocus is everything.)