The focus lies along which line?

Started Mar 24, 2013 | Discussions thread
Limburger
Limburger Veteran Member • Posts: 7,837
Re: The focus lies along which line?

fireplace33 wrote:

Here is a simple question with the hope that a simple answer is possible.

I'm assuming I know the answer

When focussed at some particular distance, does the focus lie more along the red, or more along the blue line,when using a typical lens on a typical DSLR?

The red line is a circle with the center at the camera, The blue line is a straight line.

Shoot a portrait of several people in rows. Use a big aperture lens at big aperture and there is your answer. You have to change the aperture till everybody is in focus.

Focussing and recomposing can result in oof subject due to how a focal plane and DOF work, in particular noticable with big apertures (shallow depth of field).

Your depth of field is the red line and the focal plane is the blue line. By focussing and recomposing (you pivot on a 45 degree angle) the blue line will move the same 45 degrees following the red line.

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Cheers Mike

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