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.

[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.

[ebiggs1]

"I had the firmware updated prior to purchasing the camera."

Not the firmware of the camera but the firmware of the lens?  DId you have it updated?  Canon will not include instructions on the Tamron lens in their firmware.  You need to have Tamrom update the lenses firmware.  You can't do it yourself.

Regaurdless of the negative posts, the Tamron will work.  You are on the right path to have Canon check out the Mk IV and have Tamron check out the lens.  If you are a review reader, seems to be the thing here, you will see the Tamron is a highly reguarded lens.  I have two of them.  One for Canon and a brand-N version.  They both work very well.

The G2 is even better!

[SSipple]

Yes, the firmware upgrade was done through Tamron.   My camera salesperson made me aware of thiis need when purchasing the camera, so I sent the lens for the update while I was waiting for my camera to arrive.

i love my Tamron lens.    As I mentioned, I had the version one of the Canon 100-400 and the Tamron was far superior.   My 100-400 sat in the bag collecting dust until I traded it when purchasing the Mark IV

[TTMartin]

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@SSipple wrote:

i love my Tamron lens.    As I mentioned, I had the version one of the Canon 100-400 and the Tamron was far superior.   My 100-400 sat in the bag collecting dust until I traded it when purchasing the Mark IV

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The EF 100-400 L IS II is a much better lens than either the EF 100-400 L IS or the Tamron 150-600. As I've said even with a 1.4X TC III it is sharper than the Tamron.

Canon 7D Mk II with EF 100-400 L IS II + 1.4X TC III - 560mm, 1/1250, f/8, ISO 500

[ebiggs1]

"i love my Tamron lens."

I like mine too. Obviously since I bought it twice.   Just like Canon saw the need to upgrade the 100-400, Tamron saw fit to upgrade the 150-600 super zoom.  The G2 is noticeably better in both IQ and AF. The thing is, if you need and want 600mm one of these super zooms is the way to go.  Most people don't want to or don't like fiddling around with tele converters.  f-stop penalty and IQ loss.  I know I don't.  I like the native 600mm better.

Of the current crop of lenses in this range I actually prefer the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens.  But you need to stick to your plan and have both checked out.  I am really concerned about the auto ISO.  I can see it as the culprit.

[kvbarkley]

Dumb question, but I don't think I saw it addressed.

Could you have accidently dialed in exposure compensation with the QCD? I just did that with my Rebel.

[TTMartin]

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@kvbarkley wrote:

Dumb question, but I don't think I saw it addressed.

Could you have accidentally dialed in exposure compensation with the QCD? I just did that with my Rebel.

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I think that was half the problem. The half that affected their Canon lens and was corrected by resetting the camera.

The other half with the occasional under exposure at the wide end of the Tamron 150-600 is most likely a lens issue. 

[SSipple]

TTMartin, that is a very nice image, but it is no better than what I have shot with the Tamron 150-600.   I see absolutely no reason to purchase the Canon lens to replace what is an already excellent lens.  There is an issue with either the camera or lens that needs to be addressed and then everything will be fine.   The below image was shot while on a moving vehicle.