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| p.1 #10 · Does format size reduce lens brightness??? |
Alf Beharie wrote:
I was reading a review for the Tamron SP 300mm f2.8 LD IF (60B) (Which I already have BTW) when I spotted this rather unsettling sentence:
"The big question is, how does it compare to a comparable ZD 4/3rds lens? Remember that all versions of this Tamron 300mm lens are designed for film cameras so its image circle is sized for a 35mm film frame. With a 4/3rds camera, only half that diameter is used and, as a result, you can expect the image to be slightly less bright compared to a lens that focuses all of its light onto a 4/3rds image sensor at the same f-stop."
Is this true..If I use a full frame lens on a crop format sensor camera do I actually lose f-stops of brightness at the sensor for the same f-stop on the lens?
I hope not as it would mean that when my 60B is wide open on my 1.7x crop camera it would in fact only be as bright as it is at about f4.5-f5 on a full frame sensor or film camera!
I also have a M645 80mm f2.8 N, made for much larger format sensors/film...If the above is true, how bright would that actually be when wide open on my crop format camera?
Before I read the above quote I thought that the brightness of the light in the lenses image circle stays constant per lens f-stop no matter how small the sensor format is, but now I'm confused...What do you guys think?
Doesn't make sense to me FWIW