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Nikon DSLR Cameras
D7200
Back button focusing and focus points
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<blockquote data-quote="spb_stan" data-source="post: 634676" data-attributes="member: 43545"><p>One more consideration when using the focus and recompose technique, be aware that with shallow depth of field...wide open fast lenses....Field Curvature will almost assure out of focus images if recomposing away from the point used for initial focus lock. The arc of infocus distance stays pretty much constant so by moving the angle off the center axis to the subject, you are swings that arc of constant plane radius so suddenly your subject is farther away than the focal distance locked. When doing center focus and recompose consider using a deeper depth of field by stopping down a bit so the subject stays within that depth of field. Another factor in recomposing is lens distortion is greatest at portions of the lens further from the center access. A lot of design work when into reducing that and why so many lens elements of exotic design/material is needed, but there is still some on most lenses and that distortion we see as distorted aspect ratios of length and height but it also impact distance of the focal plane, another good reason to provide a bit more depth of field when using lock and recompose technique.</p></blockquote><p></p>
[QUOTE="spb_stan, post: 634676, member: 43545"] One more consideration when using the focus and recompose technique, be aware that with shallow depth of field...wide open fast lenses....Field Curvature will almost assure out of focus images if recomposing away from the point used for initial focus lock. The arc of infocus distance stays pretty much constant so by moving the angle off the center axis to the subject, you are swings that arc of constant plane radius so suddenly your subject is farther away than the focal distance locked. When doing center focus and recompose consider using a deeper depth of field by stopping down a bit so the subject stays within that depth of field. Another factor in recomposing is lens distortion is greatest at portions of the lens further from the center access. A lot of design work when into reducing that and why so many lens elements of exotic design/material is needed, but there is still some on most lenses and that distortion we see as distorted aspect ratios of length and height but it also impact distance of the focal plane, another good reason to provide a bit more depth of field when using lock and recompose technique. [/QUOTE]
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Nikon DSLR Cameras
D7200
Back button focusing and focus points
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