Exposure issues with 5D MK IV and Tamron 150-600

[SSipple]

I seem to be experiencing e posture issues with my 5D MK IV when using my Tamron 150-600.    I did send the Tamron for the latest firmware update.   I took the camera and lens on a trip and was shooting with auto ISO and shutter priority.   All of a sudden, the exposures were dark.    I switched to my Canon 24-105, and then everything was dark.  Called Canon and they had me reset the camera settings.  Appears to have corrected the 24-105 issues.    For the most part, the 150-600 is working, but at the 150 range appears to randomly underexposed.   I looked and the auto ISO is being set to a very low ISO.    I was using evaluative metering.

called Canon and they basically told me I was using an inferior lens and that was the problem.   This has been working fine until now.  Not sure whether to send the camera to Canon, he lens to Tamron.   I used partial spot metering and the exposures seemed better.

[SSipple]

Perhaps you missed the party where the lens had worked perfectly fine with the camera until the camera started underexposing everything regardless of lens. After they reset, the Tamron still appears to be having a problem. To me , that means the issue can still be either. The camera is already on the way to Canon to look at. Tamron will also be getting a call. I cannot afford to be waiting for one then the other. I assume they will both blame each other

[TTMartin]

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@SSipple wrote:
Perhaps you missed the party where the lens had worked perfectly fine with the camera until the camera started underexposing everything regardless of lens. After they reset, the Tamron still appears to be having a problem. To me , that means the issue can still be either. The camera is already on the way to Canon to look at. Tamron will also be getting a call. I cannot afford to be waiting for one then the other. I assume they will both blame each other

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No I didn't miss that part. It just indicates to me that the TAMRON lens is the problem. So much of a problem it may have tweaked up your camera's programing with other lenses too.

[TCampbell]

Are the metal pins that conect to the gold contacts on the lens mount all looking undamaged and sprinigng in & out nicely when you press on them?

The light meter is up in the viewfinder area.  

While the camera does meter with the lens at "wide open" aperture, what "wide open" means varies depending on lens model & focal length.  So if the camera doesn't know what lens is attached then it wont be able to meter accurately.  This is leading me to suspect that the camera doesn't know what lens is attached.  

If you take a shot with the Tamron (or with any lens) and read the details in the EXIF data it should indicate which lens, focal length, and aperture were used... do you see that data or is it missing from your image?

Regards,

Tim

[TTMartin]

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@TCampbell wrote:

While the camera does meter with the lens at "wide open" aperture, what "wide open" means varies depending on lens model & focal length.  So if the camera doesn't know what lens is attached then it wont be able to meter accurately.

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Tamron relies on 'spoofing' the camera into believing it is a f/5.6 lens when it is really an f/6.3 lens. This misinformation is used to allow lenses like the 150-600 to AF on camera bodies that wont focus using lenses with a smaller maximum aperture than f/5.6. Since a simple camera reset corrected the problem with all lenses except the Tamron. The OP really needs to be looking at the lens as the issue rather than the camera. My guess is the OP will get the camera back from Canon with no issues found. 

[SSipple]

TTMartin, I appreciate your comments and your opinion.   However, I have had this lens for many years and used it with no issues.    I also used it with no issues up until last week.     At this point, I do not believe either the camera or lens can be ruled out as the culprit here.    As stated, the camera is already on it's way to Canon and I spoke with Tamron this morning and the lens is on the way back to them.

I was in Florida, and it was very wet and rainy this trip.    I suspect that the humidity and dampness caused some potential issue. 

[TTMartin]

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@SSipple wrote:

TTMartin, I appreciate your comments and your opinion.   However, I have had this lens for many years and used it with no issues.    I also used it with no issues up until last week.     At this point, I do not believe either the camera or lens can be ruled out as the culprit here.    As stated, the camera is already on it's way to Canon and I spoke with Tamron this morning and the lens is on the way back to them.

I was in Florida, and it was very wet and rainy this trip.    I suspect that the humidity and dampness caused some potential issue. 

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How long you have owned the lens is of no importance.

How long you have been using the lens with a 5D Mk IV is what is important.

Each camera Canon releases is compatible with the EOS standard. Only Canon knows what the EOS standard is. 3rd party lens makers do their best to reverse engineer Canon EOS to make their lenses compatible with it. However, Canon makes no guarantee that new cameras will work with 3rd party lenses, only that they will work with the appropriate Canon EOS lenses.

Tamron, Tokina, and Sigma lenses worked for years on Canon EOS film cameras. Then Canon made a change with EOS digital cameras and those lenses that had worked for years, would not work with the new Canon dSLRs. Some of the 3rd party lens makers came out with new chips that could be put into the old lenses to make them work, some didn't. 

When you buy a 3rd party lens and you take your chances with compatibility with future/new cameras like the 5D Mk IV.

[ebiggs1]

Again some of that is wrong.

 The big Tamron AF's at f5, not f6.3.  However, the part about it not working on a 5D Mk IV could be true.  This would be true if the firmware in the lens is not updated to include the Mk IV.  That is why I mentioned I have used that lens on many bodies but not on a 5D Mk IV.  Tamron does have a firmware update and you probably need to do that whether it is the lens or not.

Secondly, if you use DPP to read EXIF it may not show the Tamron.  You need another, not Canon, software to do that.  LR and PS both do and have no problem applying lens correction data. DPP will not.

It could be either the camera or the lens.  You are on the right track sending the Mk IV to Canon and contacting Tamron.  If the lens once worked as it should it is not the lens.  It is simply ridiculous to think that lens will not work.  It will.

[TTMartin]

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@ebiggs1 wrote:

 The big Tamron AF's at f5, not f6.3.  

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The lens AFs at the maximum aperture for the focal length used. The Tamron 150-600 is a variable aperture lens that varies from f/5 at the wide end to f/6.3 at the long end. In order for the lens to AF on all Canon cameras at the long end it has to misreport it's maximum aperture to the camera as f/5.6 instead of f/6.3. Since the lens intentionally misreports its maximum aperture at the long end, it could also incorrectly be misreporting its maximum aperture at the wide end resulting in an incorrect exposure.

To the OP do you recall zooming the lens from long end to the narrow end when you've experienced the underexposure problem?  

[SSipple]

No, I did not do that.  The issues are occurring more often when I am at the short end (150).  If you review the I Ges I posted, they were both at about the same focal length

[SSipple]

I had the firmware updated prior to purchasing the camera.   There are no additional updates available.