Canon 90D with Sigma 70-200 overexposes all pictures taken through the viewfinder (live view ok!)

[philippelang]

Hi,

I'm the happy owner of a Canon 90D. I have just bought a Sigma 70-200 lense, and I noticed that all pictures taken through the viewfinder are overexposed, no matter what I do. If I want to have a picture that is close to reality, I have to compensate the exposition with -2/-3. Tha't's a lot, not just "fine-tuning". With the other lenses, I never had this problem: Sigma 18-35mm f1.8, Canon 50mm f1.8...

Is that Sigma firmware problem? 90D firmware problem?

[kvbarkley]

Since Sigma has to reverse engineer the lens mount to get it to work, it must be a Sigma issue.

Is the aperture wide open when measuring the exposure? Try the depth of field preview button to see if the viewfinder lightens and darkens.

[philippelang]

Yes, I've been taking test pictures at aperture wide open: f2.8.

And apprently the depth of field preview button works just fine: when I press on it the viewfinder darkens when I increase the aperture f-number. And depth of field increases in the same time.

Someone mentioned having the same problem years ago with another Sigma lense, and that it was solved with a Canon 90D firmware update.. Could that be a body firmware has to be updated in order to offer support for lenses that appeared after the firmware release?

[jrhoffman75]

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@philippelang wrote:

Yes, I've been taking test pictures at aperture wide open: f2.8.

And apprently the depth of field preview button works just fine: when I press on it the viewfinder darkens when I increase the aperture f-number. And depth of field increases in the same time.

Someone mentioned having the same problem years ago with another Sigma lense, and that it was solved with a Canon 90D firmware update.. Could that be a body firmware has to be updated in order to offer support for lenses that appeared after the firmware release?

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Go to the Sigma support site.

[shadowsports]

Bravo John!

@phillipeliang, you'll need a Sigma USB dock.  Great investment if you own one or more of Sigma's Global vision lenses.

[philippelang]

I love this USB dock, and I have used it a lot for the past weeks, for calibrating my Sigma lenses. A great investment, yes!

[philippelang]

I found the culprit: it's the 90D body. A test with another 90D body shows the lens works great. I guess some hardware must be faulty, because cleaning configuration and even re-flashing the same 1.1.1 firmware did not help.

But still, that's strange: other lenses have no problem on this 90D body, only the 70-200.

[philippelang]

Maybe the problem is not a hardware problem on one of my 90Ds. I took the time to make tests, with two 90Ds and 3 lenses:

Sigma 70-200

Canon 50

Sigma 18-35

It shows the problem is Sigma-specific, when taking pictures through the viewfinder. And apparently not all 90Ds are equal: some overexpose more than others. It really looks like a complex Sigma firmware bug.

[ebiggs1]

"It really looks like a complex Sigma firmware bug."

I can't tell you any useful info about using the Siggy lens on a 90D since I don't own one but I can tell you the Sigma 70-200mm f2.8 zoom lens works perfectly on both my 1D Mk IV and 1DX. 

You might want to reset your 90D back to factory default.  You could have a setting incorrectly set and not be aware of it. Make sure you clear all "custom" settings when you do the reset.  That is probably where the error might be.

[philippelang]

I did a reset, and even a firmware reinstallation. I checked all menu configurations one by one between both 90Ds, but nothing that explains this behaviour on my second 90D.

It's really strange... Either it's a Sigma firmware bug with 90Ds or one of my 90Ds is faulty in my humble opinion.