Is the Panasonic 25mm a real f/1.4 lens?

Started Feb 17, 2014 | Discussions thread
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Paul De Bra
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A general discussion of F versus T stop would indeed be interesting.
In reply to Pixnat2, Feb 18, 2014

But of course the topic has come up several times already. There are still many people who think that the F stop really and truly corresponds to the amount of light a lens lets through whereas it is just about the dimension of the aperture. The F-stop also defines the maximum number the T-stop can be. But each lens element potentially absorbs some light so complex lenses will always have a T-stop that is measurably lower than their corresponding F-stop, perhaps more so with zoom lenses than with primes (although not "necessarily" so).

I can understand that it is confusing for consumers especially since the F-stop is published and the T-stop is not. People think that they will capture more light with an f/1.4 lens than with an f/1.8 lens but the definition of the F-stop does not imply that at all.

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