Photons Missing In Action

Started Nov 24, 2009 | Discussions thread
Jim Keye Senior Member • Posts: 2,182
Re: @ Marianne Oelund: Lens brighter than announced !?!

binary_eye wrote:

JP Scherrer wrote:

I must ADD 0.7 EV to have a properly exposed image ! ...I tried the 3 metering systems and all apertures/shutter-speed combinations: same effect everytime ! So, it seems that the lens is indeed BRIGHTER than f/4 !!!

Why would the need to apply positive exposure compensation suggest the lens is brighter than advertised? If anything, it suggests your subject is brighter than middle gray.

It seems to suggest the lens is 2/3s of a stop slower than advertised, regardless of subject.

metering is done through the lens (TTL), so differences in transmission vs. nominal aperture are accounted for.

Well...not always. First, sometimes metering is done externally. Also, there are a great many instances when people use manual exposure. When you switch lenses you have to change exposure also. Sort of a PITA when you're in a hurry, not to mention you have to decide between changing ISO, shutter, and f-stop to achieve the correct exposure again. Each affect things differently, especially if you're using a flash or a flash-ambient mixture, have the flash set on manual mode, etc. etc.

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