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Depth control, Jan-Mar 2019

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    Depth control, Jan-Mar 2019

    I found the article on depth of field a little wanting. It made the points correctly, but I think the illustrations could have been improved.
    Some people have said that focal length makes no difference to depth-of-field, and show this by taking several images at different focal lengths with a subject kept at the same size. That does seem to confirm the hypothesis. But it is not correct.
    Most EOS readers will know from the article that there are four factors controlling depth of field: focal length, aperture, distance from the focal plane and sensor size. (The sensor size is not a true factor since lenses don't change anything when changing between bodies with different sensor sizes; only when comparing equivalent field-of-view, of course).
    By keeping the subject size the same for different focal lengths, that can only be achieved by moving the camera position when the focal length is changed. So I thought that the images did not illustrate the four factors as well as they might, since the background blur does appear similar under these conditions. To illustrate the effect of each individual change, the other three factors should have been kept constant.
    For example, had the camera position NOT been changed when showing that focal length changes the DOF, the subject size would have changed, but it is background blur, not the subject, which is important here.
    Last edited by neonlamp; 30-03-2019, 17:09.
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