rocketride Loc: Upstate NY

If you mean "Is the intensity at a given place on the sensor the same for all those lenses at the same f#?", then yes. If you have a patch of, say a wall, in each lens' field of view, each lens will gather an amount of light from it proportional to the square (area) of its aperture, and each will focus that light into a patch of a size proportional to its focal length. The area of that patch will vary with the square of its linear size. So, a 100mm f/2 lens will gather 4x as much light from that patch as a 50mm f/2 lens would and then will spread it into a patch 4x the area on the sensor as the smaller lens would-- the intensity of the light within the two patches on the sensor would be the same. (I'm ignoring the effects of manufacturing variation in actual focal length, difference in transmission, etc.)

If you mean something else, then maybe not.

DJO

The Answer is yes.

Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga

Actually, that is not correct. Reason being, as I stated before, the T stop factor may be different even though the F stop is the same. Add to that manufacturing variations ( lenses are made to a range of tolerances, same applies to focal lengths, while a lens may be stamped as 200 mm, it's actual FL may be 199.5 mm) Thus there can be differences between one F2 lens & another, even within the same manufacturer lens line...

rocketride Loc: Upstate NY

Unless there's something wildly outside the usual specification tolerance, the difference in T-number between two lenses of similar F-number and 'vintage' isn't going to amount to a big difference in shutter speed needed to correctly expose in a given illumination. Big differences in the number of elements (i.e. prime vs zoom), a big difference in age (resulting in one lens having better AR coatings than the other), or the glasses used in a design can make a bigger difference in T-number, though.