[dms]

With a 1.5 cropped sensor (would be exact if was 1.414 cropped sensor--but a trivial difference) if one keeps the same FL the DOF are the same if the cropped sensor aperture is one stop smaller (e.g., f/8 on FF is equivalent to f/11 on an APS-C). Put it this way: you need to enlarge the image more on the cropped sensor and thus less DOF at same aperture.**

If you are not very experienced I think it is best to first work out the equivalence--as described above. Then you can, for example, close an additional stop for large prints; and based on your results you may decide to change by 2 stops, or whatever; but I think it is a good idea to first make the adjustment for sensor size. This way you are not changing two variables at the same time.
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** If that seems counterintuitive, on the APS-C camera, if one chose a wider FL to get the same field of view, and kept the same f stop, the DOF would be greater.

---------- Post added 11-10-20 at 07:44 PM ----------

Depth of field depends on the focus distance, focal lenght and the aperture you use. ... The problem of those markings is, that they are usually meant for analog/film photography. Depending on your camera (Sensor/MP) your resolution with DSLRs is usually higher than the resolution of film, therefore the actuall depth of field is smaller than indicated on the lens.

If you are interested in hyperfocal distance shooting and the like, it is probably better to use a distance calculator in the internet where you can also input sensor size and resolution

The DOF only depends on the print size or viewing size, not the sensor resolution. You may choose to print larger, so in the field, when you may need to get an image fast, use the DOF markings on the lens (e.g., for hyperfocal distance), and then close a stop (or whatever) depending on print size and cropping. (I actually remember hyperfocal distances for my most used FL and aperture, so I can set it quickly.)

Also (to answer another post), checking the 15mm ltd, I see it has: focused at infinity a DOF from infinity to 3 feet, at f/8. This matches DOF Master website for APS-C, while FF would be same at f/5.6. So presumably the DA LTD's are properly marked for APS-C.

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Last edited by dms; 11-11-2020 at 12:14 PM. Reason: Forgot to say f/8 on APS-C. Fixed typo--should be infinity, not zero, in last paragraph.

[leekil]

Comparing an M 20mm to a DA 21, there is a smaller depth of field on the scale for f/22 on the DA21than the 20mm lens. And the extent of rotation of the lenses are very similar from the closest to the farthest focus, but the depth-of-field scale printed on the DA21 takes up about half the length on the top of the DA21 (maybe it's really 1/1.5?) than on the 20mm, which seems to further indicate that the scale is accurate for the APS-C sensor.