Re: PHOTO-3D digest 1293

[P3D Michael Kersenbrock <michaelk@xxxxxxxxxxx>]

> The added speed? If f/2.7 is truly the speed of the lens, it would be about 2/3 
> of a stop faster (f/2.5 being a full stop from f/3.5?). I suspect it is not, as 
> I think it would be hard to stretch a triplet this far without major 
> abberations... as I said in a previous post, perhaps an attempt at a marketing 
> differentiation, which clearly worked! (Someone replied that the public was/is 
> too savy to fall for such a ploy, which I say is dead wrong, the public falls 
> for junk like this all the time, then and now.)

Could they have been playing games with specs vs. coatings?  What I mean is
the relationship between light transmission and f/stop not being one to one
due to other factors like lens coatings.

So.... *if* in that timeframe, lenses were often non-coated or only partially
coated such that a more fully coated Wollensak lens transmitted 2/3'rds
of an f/stop more than a non-coated 3.5 lens, then maybe their marketting
department's f2.7 spec is an "equivalency" spec, meaning that it would take
a non-coated lens of f2.7 to have the same light transmission of their lens,
and therefore it "is" a f2.7 lens.  In marketting-speak.  :-)

I'm just guessing.... giving the cynical among us more food to stew on.  :-)

Mike K.


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