Screen brightness goes up momentarily when half-pressing (Live View)

Wikzo

EOS M50
Apr 23, 2020
26
11
When I half-press on my R6, especially when the AF point is on a darker spot, sometimes the screen momentarily gets brighter before going back to the correct exposure.

It's difficult to search on Google for this, but I think it's related to how Live View mode works on cameras (vs. DSLRs). I found this regarding the EOS 7D, which might be related:

If you point the camera in a different direction, it might throw off the Live View image's correct brightness momentarily. Wait until the brightness level stabilizes before shooting.

It's not related to Exposure Simulation, since it happens even while turned off.

My guess is that the AF system sometimes need to increase the exposure in order to obtain focus, similar to the AF-assist beam. But I am curious to know what exactly is going on and why it only seem to happen in Manual mode.
 
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Wikzo

EOS M50
Apr 23, 2020
26
11
Yeah, it's a bit strange. I would like to know if this is inherent to Live View (aka mirrorless cameras).
 

Joules

doom
CR Pro
Jul 16, 2017
1,664
2,015
Hamburg, Germany
Originally I would have guessed it's the lens opening fully since Canon does AF wide open. But if you say it is especially noticeable with dark subjects, than it makes no sense to me that the aperture would be closed in the first place.

Could it be that Canon simply injects the frame they take for AF acquisition into the display stream instead of missing one? If so, they trade a short lag in the display against this spike in brightness. It would certainly explain why a darker subject provokes the effect more clearly.

However, it is one of these things we're I would think they could just adjust the ISO for that frame to offset the exposure time. But maybe that's just not a capability of their likely hardware based image pipeline.
 

Act444

EOS R
May 4, 2011
1,133
203
This happens with my RP (and on every press). Also occurs when using the EVF. Interesting that it hasn't been fixed on the R5/R6 yet...