On this page, I present Sony RX100 M1 photos taken under similar conditions but with varying aperture to demonstrate how fuzziness caused by diffraction sets in at smaller apertures.
Note: See also page Calculating the Optimum Aperture for Different Sensor Sizes (Diffraction Limit) for a general discussion of diffraction.
As you stop down, "diffraction" sets in and reduces image sharpness. The more you stop down, the larger diffraction effects get. Diffraction can be described as "the spreading out of a light beam when it's 'squeezed' though a small aperture." The smaller the aperture, the more the light spreads out.
This works differently for different sensor sizes, and you can read more about this on page Calculating the Optimum Aperture for Different Sensor Sizes (Diffraction Limit). All in all, the generalized results for the "optimum apertures" are:
Please note that this are limits that diffraction sets to image quality; it sets in at much smaller f-numbers, but this is a "gradual" process (for details, see page Calculating the Optimum Aperture for Different Sensor Sizes (Diffraction Limit). Also note that these limits, may be a "matter of taste". Some authors maintain that diffraction sets in for 1" cameras already beyonf f/5.6.
In the following, I present sections from example photos that I took at different f-numbers (up to f/11, the smallest aperture on the camera) and with the Sony RX100 M1 to look for diffraction effects. Of course, this is just a "quick-and-dirty" investigation. Nonetheless, diffraction effects can be found on the computer screen at least at 100% magnification. What this means in your photographing practice, is up to you...
Using the following photos taken with the Sony RX100 M1, you can observe on a computer screen at 100% magnification how diffraction increases with f-number.
About the photos:
The photos were taken with a tripod at the f-numbers f/4, f/5.6, f/8 and f/11 in A mode. Distance was set to infinity using AF and then fixed by switching to MF. ISO was set to ISO 200, and a focal length of about 35 mm (equiv.) was used.
The images below are 100% sections. Click the images to download or view the photos in full size.
f/11 (maximum f-number)
Note: Here are some more photos that can also be used for this purpose. They were taken with focus at infinity to be compared with photos where distance was set to the hyperfocal distance: f/5.6, f/8, f/11.
My basic conclusion from this test is that I will not use an aperture value of higher than f/8 on the Sony RX100 M1. The deterioration at f/11 is visible, when I view the test photos in full size on the computer screen.