[boondaburrah]

It is, but when you take cropping into account it's like this: If I shoot 2 photos, one with a 50mm lens at f/2 on 35mm film, and one with a 35mm lens on APS-C, I need f/1.4 to achieve the same depth of field, because everything is smaller. The image will however be brighter, because I shot at f/1.4 (assuming ISO and shutter speed are constant).

It takes less light to illuminate a smaller sensor using a smaller lens (because the image projected on the sensor is smaller), so I need to open the aperture less to get the same f-stop number, but I have achieved less bokeh (more depth of field) at what is the equivalent f-stop of a larger lens in doing so. The bigger you need to blow up the image to fill the sensor, the dimmer it gets, so more open aperture to get the same f-stop, but your DoF is shrinking when you do so.

It took me a long time to wrap my head around it this far, let me know if I'm making sense. I'm rambling a bit because I've not had to put this into words before, and could be way off base.