DPReview.com is closing April 10th - Find out more

To stack or not to stack

Started Sep 26, 2019 | Polls thread
gardenersassistant Veteran Member • Posts: 9,656
Re: Larger DOF with larger sensors (not a typo)

Pixel Pooper wrote:

gardenersassistant wrote:

I can see that the lens without the teleconverter has a wider angle of view, and that the background has a wider field of view. But I'm scratching my head a bit about the implications of this regarding the DOF. The field of view at the focal plane is the same, so Isn't the difference in DOF being caused solely by the difference in exit pupil rather than the difference in angle of view or the difference in field of view in the background?

Depth of field depends on the angle of the cones of light from the subject passing through the aperture.

Ah! Another little gem. Thank you.

To keep the same magnification with double the focal length, you must double the distance to the subject, so the light cone becomes narrower unless you also double the aperture diameter, which gives you the same f-number.

So if, with the same magnification, you double the distance to the subject, you halve the effective aperture diameter? (Or the exit pupil diameter?) Thus doubling the f-number?

To keep the same magnification with the same angle of view, your subject distance is the same, so the light cone has the same angle at the same aperture diameter. With a smaller sensor, the same angle of view requires a shorter focal length, which gives you smaller f/number.

So the effective aperture and the angle of view change in lockstep, so you can use either in assessing the amount of/changes in DOF?

Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow