Originally posted by Class A No.
There is no difference between "DOF f-stop" and "light gathering f-stop".
Falk has answered this one already, but maybe not directly enough to be noticed.
I have to disagree.
That statement considers only the total amount of light entering the lens, not the light intensity at the sensor needed for a given exposure which is how the concept of f-stop is used by photographers. With the same subject, perspective, light level, sensor sensitivity, shutter speed, and f stop, you will get equivalent exposures regardless of sensor size. That's why the rules for exposure are the same for all formats. There is no format setting that needs to be taken into account on an external exposure meter.
If what you state is the case, then if you took any camera and lens and aperture/shutter/ISO settings, with a given Ev, and the same grey card subject at a given distance, and take a "correct" exposure with the full sensor, then mask off the sensor so 1/13 of the sensor area is exposed, you'd have to increase shutter speed or ISO by about 5.5 stops to get the same exposure on the masked sensor, and that's just not true. The exposures for the exposed area on the masked sensor and the same area of the unmasked sensor would be the same with the same shutter speed.
f-stop is the ratio of the entrance aperture diameter to the FL of the lens. Film or sensor format does not enter into the equation.
Scott