90D and Canon 300mm f4 L IS USM inconsistencies in exposure

[Wandalynn]

I wanted to see if (1) anyone else has had this problem and (2) if there are any fixes. First, let me say that my Canon 300mm lens has worked perfectly on my 70D, my 6Dii, and my R cameras. Add to that that all of my other Canon lenses perform perfectly with the 90D. I almost exclusively shoot in AV mode, mostly nature closeups, and mostly use evaluative metering, sometimes spot.  Taking pictures with the 90D + 300 through the VF, almost all of them are severely underexposed, almost black. Taking pictures with same lens using Live View, the exposure is fine. Again, that never happens with my other lenses on this camera, and I have no problems with this lens on my other cameras. Input appreciated.

[Chris_N]

I am glad to hear you solved the problem. What was the actual solution? To turn off auto iso or to change the metering mode?

Kind regards

Chris

[Wandalynn]

Chris_N, I'm not sure--LOL--but restoring to factory defaults and shooting per ebiggs' instructions the lens worked perfectly using the VF. Apparently I had some setting (yet to be discovered) that was causing a conflict. I'll definitely be mindful of the settings I make. Thanks.

[timmyleeturner]

I can certainly relate to this issue... I've taken hundreds of thousands of photos on my 70D's using the same 

Canon EF 75-300mm f/4-5.6 IS USM in outdoor, bright and sunny days and I recently upgraded to 90D.  I've spent the first 4000 photos trying to deal with overexposure.  I'm adding a CPL filter today, but I've already lowered the default brightness by 3 notches and my settings are extreme to keep from overexposing compared to my other cameras.  Probably sending the camera back. I have adjusted metering modes, ISO (which I MUST keep on 100 with this camera) Setting the camera on Auto fully overexposes every photo.

[Wandalynn]

@timmyleeturner, my lens performance greatly improved after I made the last firmware update, although my specific issue wasn't shown in the description of the update so if you haven't updated that, try it first. Some of my photos show up a little dark but not nearly as frequently or severely as before. The 90D has so many improvements over the 70D though that I hope you won't have to return yours. Wanda

[Waddizzle]

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@timmyleeturner wrote:

I can certainly relate to this issue... I've taken hundreds of thousands of photos on my 70D's using the same 

Canon EF 75-300mm f/4-5.6 IS USM in outdoor, bright and sunny days and I recently upgraded to 90D.  I've spent the first 4000 photos trying to deal with overexposure.  I'm adding a CPL filter today, but I've already lowered the default brightness by 3 notches and my settings are extreme to keep from overexposing compared to my other cameras.  Probably sending the camera back. I have adjusted metering modes, ISO (which I MUST keep on 100 with this camera) Setting the camera on Auto fully overexposes every photo.

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What is the aperture setting for the overexposed images?  Maybe you have a stuck aperture. 

You can do a quick test of the automatic aperture by using the DOF preview button.  The camera tries to focus at the maximum aperture setting, which allows the most light to enter the camera for focusing and metering.  So, dial in an aperture setting of f/16, which should create a significant change in the image when you press the DOF Preview Button.

[EDIT] While you are checking settings, check your exposure compensation setting, too.  Also, try to reset the camera back to the factory defaults.

[Chris_N]

In addition to upgrading the firmware on the 90D try upgrading the firmware on the EF 75.300 lens.

I have exactly the same problem when using my Yongnuo YN14EX ring flash. The camera will overexpose flash pictures by 3 stops and I need to keep the iso on 100 to avoid further overexposure. The flash worked fine on the 550D. Of course its not a Canon flash and Canon are not obliged to fix the problem. Yongnuo don't have a firmware upgrade for this flash. 

But as you are experiencing similar problems with a Canon lens on the 90D it does make me wonder if upgrading the lens firmware might fix the problem. I would try that first before sending the camera back.

Kind regards

Chris

[timmyleeturner]

I'll see if there are any updated firmware for the camera, I don't know how you'd update firmware on a Lens? I found a special running on camera, lens calibration... I"m gonna try that.

[Chris_N]

The latest 90D firmware is 1.1.1. I checked and there is no available firmware update for the 300mm f4 L IS USM. (Sorry, my mistake)

https://www.canon.co.uk/support/consumer_products/products/cameras/ef_lenses/is/ef_300mm_f4l_is_usm....

The only other thing to check is if the contacts are good and the aperture is working properly. You might also test the lens on another 90D body if you can get hold of one. Maybe, you could also have both the body and the lens checked at a camera service centre. 

I hope the programe you found can help to tune the equipment and you can solve the problem. It can be very frustrating when expensive, state of the art equipment doesn't behave as it should. 

Please let us know how you get on.

Kind regards

Chris

[timmyleeturner]

I will post back, pretty much have a problem with over exposure and tak focus..  But if you set this camera to auto, you have to edit the picture quite a bit, if you can even use it.

[Wandalynn]

@timmyleeturner Updating the firmware is very easy because Canon gives you complete instructions in the zipped folder that you download from the Canon site. I prefer to use the SD card method. Go to the 90D page on Canon and then to the Firmware tab. There are all sorts of instructional videos out there about updating firmware but I HIGHLY recommend using Canon's instructions, they are EASY TO FOLLOW, with pictures of the screens, etc.