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So I was shooting in autofocus with a small aperture (f11) and my camera (Canon RP) gave a very deep depth of field where everything is in focus. I tinkered a bit and switched to manual focus (with everything else stayed the same). And suddenly the DoF was very shallow; the background was blurry. Can someone explain how moving the focus ring in manual focus affects DoF. In manual focus mode, does it now matter what the aperture is anymore for DoF?

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    \$\begingroup\$ Do you mean DoF was shallow when looking through the viewfinder, or in the captured photo? \$\endgroup\$
    – Kahovius
    Commented Feb 2, 2022 at 23:55
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    \$\begingroup\$ When you switched to manual focus, what did you actually focus on? \$\endgroup\$
    – osullic
    Commented Feb 3, 2022 at 0:21
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    \$\begingroup\$ Manual focus might have disabled DoF preview mode, which may now need to be activated manually by pressing some button. \$\endgroup\$
    – Ruslan
    Commented Feb 3, 2022 at 16:26
  • \$\begingroup\$ Actually I'd check the EXIF data for aperture. Some models even store the focus distance verbatim there. \$\endgroup\$
    – U. Windl
    Commented Feb 3, 2022 at 21:37

3 Answers 3

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I haven't used this camera, but it has a "Manual focus magnification' feature. On my Sony Alpha a550 DSLR, it automatically sets aperture to full open to help you with precise focusing. The actual picture is taken with your chosen aperture.

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Manual or autofocus has no influence over the depth of field. Something else has changed (assuming aperture remained the same), like the focal length (longer zoom, shallow focus) or the distance to the subject (close to the subject: more distance difference between subject and background).

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The simple box camera, Kodak Brownie type, is a fixed focus camera. With no focus adjustment, they are pre-focused on a sweet spot focus distance called the hyperfocal distance. Such a setting delivers maximum depth-of-field. The span is about 1 yard (meter) to infinity. You can manually set your camera to the hyperfocal distance if you know the settings. As a rule of thumb, to maximize depth-of-field, set f/16 (aperture) and manually focus at 10 feet (3 meters). Likely, when you observed that the depth-of-field was wide-ranging, your camera was operating at or near the hyperfocal distance. You can consult tables and charts plus you can Google hyperfocal distance. I set my camera at f/16 and set the focus at 10 feet. Better, find the diameter of your lens (iris) setting, Say your lens is a 50mm focal length set the f/16. The working diameter of the iris is about 50 ÷ 16 = 3.3mm. To find the hyperfocal distance (approximately) multiply 3.3 X 1000 = 3300mm, about 3 1/3 yards/meters. Manually set the focus to this distance (about 10 feet) and you will be amazed at the span of the depth-of-field. When you switch to auto mode, the magic setting you accidentally achieved went by by.

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