Mike Halliwell 
, Feb 02, 2012; 07:29 a.m.
Following on from a previous thread topic, I thought the newer Nikon DSLRs had a lens specific exposure compensation correction similar to AF Fine Tune. Not sure why I thought this, 'cos they don't!! (or if they do..How Do You Do It?)
Looking back through various posts it seems many people need to apply Exposure Compensation on a lens specific basis EVERY time they mount that lens. ie My D700 always needs -0.7EV with my 70-200 AFS VR, but is fine with all my other 8 lenses etc...
How hard would it be to add this to the lens' profile? After-all, the aperture mechanism doesn't have/use physical stops as such, it needs to be locked at it's lowest eg f22, and the camera drives it to where it wants. In G lenses this is even more a remote process.
Matt Laur 
, Feb 02, 2012; 08:33 a.m.
I can see why that might be handy ... but have you considered just having Nikon adjust your 70-200/2.8's behavior if it's that consistently wrong? That's much too nice a lens to have to keep messing with it like that.
Mike Halliwell , Feb 02, 2012; 09:30 a.m.
Hi Matt, is it a case of re-programming the lens chip? It's not such a problem, as I'm usually using this for event horses and rarely need to change over on the day. It would be nice to tweek some of the others just a little!
I initially thought on a G lens that the aperture was moved electronically from within the lens itself so couldn't be subject to misalignment as such, but see it is still infact a physical mechanism unlike the AF> AFS difference. Electronically actuated apertures must be next? I imagine that's a point of no return though...:-) . Built in Legacy support no doubt!
But you're right about the nice glass, it cost more than my car!
Phil Evans , Feb 02, 2012; 09:58 a.m.
Jim Momary 
, Feb 02, 2012; 10:09 a.m.
On something like the Nikon D7000, could this issue be addressed by making one of the two "U" settings have an EV offset? So, in essence, U1 or U2 would become a user profile for that particular lens that Mike mentions... twist a dial and yer done.
Jim
Michael Bradtke , Feb 02, 2012; 10:21 a.m.
Sounds like a sticky aperture to me. I have friends who use the 70-200 to shoot equestrian events. One of them has had to send his back ti Nikon twice to have the aperture fixed. Both times it was sticking and giving him over exposed images.
Using TTL metering I would not expect to have to use exposure compensation when switching from one lens to another.
BeBu Lamar , Feb 02, 2012; 10:27 a.m.
First it's not a case of f/stop vs T/stop because the meter is thru the lens and would compensate for any such differences.
Second a fixed amount of exposure compensation I don't think will correct the problem because at max aperture there should be no error. The error is there is in in the amount of diaphram movement and if it is then it would be a different amount of error for each stop.
Mike Halliwell , Feb 02, 2012; 10:30 a.m.
People seem to be in love with t-stops at the moment!
Am I odd in wanting all my lenses to give pretty much the same exposure? (for given settings)
Light meters give 'settings' to reproduce 18% grey etc. etc... I set those settings on my lens and expect the image results to be fairly close, within 1/5 stop. The amount of difference people are experiencing is sometimes as much as a WHOLE STOP. If it's messing up peoples ability to compare two different 10-20mm lenses, there's a problem somewhere.
The reason I am persuing this is that people who have this problem have it with one or two lenses in particular. I fully understand the difference between f & t stops, but this seems to be either a case of v.bad calibration or lens-body communication failures.
Consistency should be very easy to ensure with Lens Specific Exposure Compensation, if this means making f stops and t stops, err.. the 'same', that's OK! Afterall, a mathematically derived number ie the f is pretty pointless!
Jim, Yup, I guess it could. It would seem to be easier just to add this 'correction' in just the same way as an AF correction in Fine Tune is stored for each CPU'd lens.
The camera ID's which lens it is, knows it's gotta focus 2% closer and correct the exposure by -0.7EV. That cannot be hard?
Mike Halliwell , Feb 02, 2012; 10:38 a.m.
TTL will not help with Manual Exposure differences. If it can be corrected with normal camera based exposure correction, then equally it can with 'saved lens specific data'. These differences are when comparing new lenses from different manufacturers.
I'm not sure if the aperture error will be different for each setting, that would imply very bad design/construction/wear problems etc.
To anyone who is curious as to where this started, its here..
http://photo.net/nikon-camera-forum/00ZxBG
Brooks Gelfand , Feb 02, 2012; 01:19 p.m.
I think Phil is correct. Since the OP is shooting in manual exposure, this does sound like the f/stop vs t/stop problem.
The 70-200 has many element and by the laws of physics will transmit less light than a lens with fewer elements. Thus to get the same light to the sensor using the 70-200, one must open the lens more than a lens with fewer elements. In any mode other than manual, the TTL meter would perform the compensation for you.
By applying a -0.7 EV, you have arrived at your own t/stop compensation factor.
Since t/stop is used mostly in cinematography and since more and more DSLR cameras have movie capability, perhaps camera manufacturers will include a t/stop calibration feature in future cameras.
