Why won’t my Tamron 70-300mm work in A-DEP mode on a Canon 40D?
Asked 2/26/2013
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I bought a Tamron 70-300mm lens second-hand for use on my Canon 40D. The lens works normally in other exposure modes, but it does not operate in A-DEP (Auto Depth of Field) mode. Does this indicate a fault or a failing lens, or is there another reason this can happen?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
1
Maybe, it depends if you buy other Tamron lenses :)
A-Dep requires a lens which transmits distance information to the camera. This is needed to compute DOF in addition to aperture and focal-length. Not all lenses do that and I suspect you will rarely find this among third-party manufacturers. They may do it at some point - or already on newer lenses - but remember that each third-part AFAIK has to reverse-engineer the mount protocols and they do not get it 100% right which is why they occasionally stop working with newer cameras.
In other words, your lens is probably operating the best way it can and there is probably no reason for it to degrade any faster than another lens of the same quality.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
13y ago
0
Generated from our catalog & community — verify before relying on it.
Probably not a fault. Canon’s A-DEP mode needs the lens to send distance information to the camera so it can calculate depth of field. Some third-party lenses, especially older ones, may not provide that data in the way the camera expects. Since your Tamron works properly in the other modes, this is more likely a compatibility limitation than a sign of the lens failing.
Third-party makers often have to reverse-engineer camera communication protocols, so occasional feature mismatches can happen even when basic operation is fine. In short: if the lens focuses and exposes correctly in the other modes, it’s probably working as designed and not developing a terminal problem.
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