Photons Missing In Action

Started Nov 24, 2009 | Discussions thread
OP Marianne Oelund Veteran Member • Posts: 7,749
Metering anomaly
1

JP Scherrer wrote:

Now... I bought a 300mm. f/4 AF-s a few weeks ago (and enjoy it thouroughly BTW)... I noticed one thing: it's the ONLY lens to which I have to use the Exposure Compensation Button on my D700 ! So, it seems that the lens is indeed BRIGHTER than f/4 !!!

That does not follow. What you are observing, is only a metering problem; by adding the -0.7EV, you are correcting the error.

You can confirm this by photographing a blank wall that's evenly illuminated, with your 300/4, and then another f/4 lens wide open (note: 200-400/4 VR is not recommended for this comparison), keeping all camera settings manual and unchanged. Then compare the histograms (reading the furthest-right values shown, since the dimmer values are due to vignetting, which varies between lens models).

How do you explain this ?

I've never used the 300 f/4, so I do not have any experience which I could offer as explanation. I have noticed, however, that exposure metering can be affected greatly by the optics used.

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