D lens data screws up TTL BL direct flash

Started Dec 4, 2012 | Discussions thread
WFulton
Senior MemberPosts: 2,596
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Re: No EXIF
In reply to _sem_, Dec 7, 2012

_sem_ wrote:

I believe encoders in the majority of lenses works fine, otherwise we'd witness more complaints. Maybe certain climate makes the encoders fail even sooner than fungus shows up on glass. The contacts look gold-plated and some sort of contact grease is used, but that may not last forever.

A service manual probably would be interesting, but I don't find any. Sites claiming to have several to many seem to have nothing. If you can point to one that shows anything, it would be appreciated.

I feel sure CPU communication output needs an encoder, but that part seems to work OK. Aperture and zoom seem well reported, without error. Just distance is crap. I think that is the input.

Lenses do not know distance. Someone can calibrate them, and make a mark, and say This spot of rotation is 5 feet. But all the lens does is rotate, and in many cases, focus rotates to a very different spot at wide zoom or narrow zoom. And it acts as if it only has one set of a few markings for all zooms. I cannot imagine that repair is going to do it. My 12-24 lens has already been rebuilt by Nikon (replaced body housing as way to repair filter threads), and they must test a few things. But this 16-85 is still as shipped. And the other lenses are not prizes. It all seems pretty crude, yet it can affect the default TTL BL direct flash.

And I'm sure Nikon wouldn't bother installing them into lenses if there were no advantages. AFAIK it has sth to do with delivering a suitable amount of flash power for a certain distance rather that using a straight TTL formula with the aim of avoiding making black (white) dogs middle-grey.

I think it is because TTL direct flash in front of open backgrounds typically tends to overexpose, trying to brighten a dark background. Instead of watching clipping, they try to watch distance, which might be elegant, if they simply knew the distance.

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