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I carry the Sony RX100M3 with me and usually shoot aperture mode (generally around f/5.6 for deep dof). I notice that my camera allows for very high f-stops up to a maximum of f/11. If I calculate the 'equivalent' f-stop for a 35mm frame, and using the Sony RX100M3 cropfactor of 2.7, this would result in an extremely high equivalent f-stop of almost f/30.

I was wondering: What are these high f-stops good for when using a compact camera like the Sony RX100 series? I know that for very small apertures, the image may suffer sharpness due to diffraction. So why would one bother to use f-stops as high as f/11 for a compact camera?

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    \$\begingroup\$ IIRC on some compact cameras the higher f-stops are actually a neutral filter to reduce the light on the sensor, not a a smaller diaphragm (which would generate too much diffraction). \$\endgroup\$
    – xenoid
    Commented Apr 4, 2020 at 19:52
  • \$\begingroup\$ Oh, that is interesting.I did not know that. However, I'd like to note that the Sony RX100 has a mode to select the ND filter on and off. I believe this is not the case for Sony RX100. Of course, this could be for other compact cameras. \$\endgroup\$
    – Nadia Merquez
    Commented Apr 4, 2020 at 20:33

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Put on a closeup lens, zoom to max, and depth of field will be a problem even for the smallest aperture. I do a number of closeups with a Panasonic Lumix DMC-FZ200 which has a 1/2.3" sensor with a crop factor of 5.6 (namely about twice that of your camera) and F8, corresponding to F45 on a full-frame, often ends up limiting. Yes, there is diffraction. However, it does yield (at the cost of additional noise; but with a flash there usually is no lack of light so the base noise level at base ISO is moderate) to sharpening, and as opposed to defocusing, the effect of diffraction is uniform across the image.

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  • \$\begingroup\$ Thank you for answering. If I interpret correctly, the answer boils down to, in certain circumstances (f.e. we have a small subject distance with max zoom) we may prefer a higher f-stop in order to preserve a deep dof at the cost of diffraction effects. \$\endgroup\$
    – Nadia Merquez
    Commented Apr 4, 2020 at 20:30
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f-Stop is Actual Focal Length divided by Diameter of the Opening.

Crop factor is a short hand referring to sensor area compared to a standard 35mm film frame. It has nothing to do with actual optics. A 5.6 is a 5.6 is a 5.6, no matter the sensor size and hence the crop factor.

A 200mm lens is still a 200mm lens on a 2/3 crop factor despite our treating it as a 300mm equivalent. It's a visual effect due to a smaller image segment being presented in the same visual frame as a larger image segment. Optically it's still a 200mm lens.

High f-stops reduce light and increase depth of field.

Here is a long and well written article on these kind of recurring questions. sensor-crop-factors-and-equivalence

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  • \$\begingroup\$ Thanks for the clarrification. I apologize, I may have been sloppy with the terms. I am familiar with the basic concepts of exposure. \$\endgroup\$
    – Nadia Merquez
    Commented Apr 4, 2020 at 20:38

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