RF 100-500 on R7 AUTO ISO issue. Is it normal?

[kepAE1]

I purchased the Canon RF 100-500mm lens last week. I have had several days now trying to get used to it with my Canon R7. (Was using the Tamron 100-600). I have an issue that am not sure it is a defect or normal.

When using AUTO ISO in any mode (NOTE: that I always shoot in manual), when I change the zoom and refocus, the ISO setting becomes frozen at some apparently random number. I have to reset AUTO ISO (done easily via the ISO button), to force camera/lens back to AUTO ISO function. In the instruction manual it mentions that you will likely need to refocus after changing zoom, but there is no mention about AUTO ISO. Kind of a pain when trying to capture fast moving wildlife.

Any help?

[kvbarkley]

Is the exposure correct?

[kepAE1]

Yes.   Except for ISO, which is stuck on a level that is too low. View Finder still says that I am in AUTO ISO mode, but the camera is not changing the ISO.  Moving the camera and refocusing does not force the AUTO ISO to correct.  When I press the ISO button to reestablish AUTO ISO, it starts working again.  I also just discovered that if I do nothing, AUTO ISO will start working in about 10 seconds.

[kvbarkley]

If the ISO is "too low" than the exposure is not correct.

[kepAE1]

Not sure what you are asking.  Define Exposure.  Yes the exposure is not right because the AUTO ISO is not adjusting based upon the set aperture and speed, which is the problem.  When the AUTO ISO is working (with the same set aperture and speed), then the exposure is correct.

[kvbarkley]

Do the pictures come out OK when the ISO is too low.

[kepAE1]

No, the photos are not exposed correctly when the AUTO ISO is "stuck".

Hope this clarifies the issue. Here are some real scenarios. All photos taken in manual mode, 1/3200 f9, Auto Iso. Changing only the zoom level on th same subject.

1) At 100mm, photos exposure was correct. Auto ISO was 2500.
2) Zoomed to 500 and set AF. This time Auto ISO became stuck at ISO 10000, Photos was over exposed.
3) Waited for 10-15 secs, and Auto ISO kicked in and AUTO ISO was corrrectly set to 1250. Photos exposure was fine.

I then selected another subject.
1) At 100mm, photo exposre was correct. Auto ISO was 1500.
2) Zoomed to 500 and set AF. Auto ISO became stuck at ISO 500, Photos was under exposed.
3) Waited for 10-15 secs, and Auto ISO kicked in and AUTO ISO was corrrectly set to 1000. Photos exposure was fine.

Similar occurances happnen when changing zoom from 500 to 100 in between.

Appears that for some reason the R7 with the rf100-500 is often VERY slow in setting the correct ISO exposure and while it is "thinking" the actual setting is randomly set and stuck at some level.

I do not experience this issue with my Tamrom 100-600 or my Canon EFS 55-250. Do not think it is an issue with the rf18-150.

[kepAE1]

FYI. Both camera and lens have the latest firmware.

[kvbarkley]

I suggest you call Canon about it, since the lens is under warranty. Their support staff have the equipment there so you can troubleshoot in real time.

[kepAE1]

Thanks.  I may try resetting the R7 first.