On Sun, 18 Aug 2002 20:25:03 GMT, info@internet-real-estate.com wrote:
>In article <3d609a3b.2919303@newsstand.cit.cornell.edu>, d_ruether@hotmail.com wrote:

>> The physical size of the lens has little to do with
>> "light gathering". The widest relative aperture
>> ("f-stop") available indicates the "speed" of the
>> lens, not its size...

>You've never used telescopes much, have you. The bigger the objective
>lens, the more light gathering ability.

Different issues...
With essentially parallel rays through the lens (long
teles), there is some association of lens front size and
"light gathering" ability - though the actual f-stop (the
most relevant measure) is still related to both diameter
*and* FL; with short FL lenses, there is little reasonable
correlation between lens front diameter and its "speed"...

>A pair of binoculars with 70mm objectives will be MUCH brighter than the
>less expensive ones with 35mm objective lenses.

Well, yes, unless the 70mm objectives are twice the
FL (magnification) of the 35mms, in which case, they
will have the same brightness, all else being equal...
(10X70 and 5X35 binoculars will have the same
brightness...).

>Two cameras ... both set at f4 for example, but one with a much larger
>objective lens ... WILL be much brighter.

????????????
I don't think so................! ;-)
The relative aperture (all else being equal, like
transmission efficiency, illumination evenness,
accuracy of opening, etc.) determines the brightness
of the light passing through, regardless of front
size or FL (but depending on their relationship...).