Exposure changing while shooting High Speed Continuous and Servo Focus with the R6

[kevinbarre]

I can shoot a static subject in static light using the High Speed Continuous drive mode on the R6, and the first two frames will be correctly exposed, but all subsequent frames will be overexposed. 

Trying to figure out if there is a setting to keep the exposure automatically locked. I have it set for Center-weighted Average metering, and I have "AE lock metering after focus" set to locked, but this doesn’t seem to actually keep it locked when using Servo focus. Also, it's odd that it always jumps up in exposure and will stay there as long as I hold down the shutter. 

I'm using Aperture priority and Auto ISO. For a static shot using High Speed Continuous drive mode and mechanical shutter, I get the following frame stats:

Frame 1: 1/320 F2.5 ISO 2500

Frame 2: 1/320 F2.5 ISO 2500

Frame 3: 1/250 F2.5 ISO 4000

Frame 4: 1/320 F2.5 ISO 5000

Frame 5 (and all subsequent frames): 1/320 F2.5 ISO 5000

I get it that it's an Auto ISO issue, but this does not occur if I set the focus to One Shot. It will hold the exact same exposure for as long as I hold the shutter. Wondering if there's a way to lock the exposure for as long as I have the shutter button held.

I'm not interested in using the AE Lock button to hold exposure as I shoot, even though this DOES fix the problem. I'm wondering if there is a menu setting that will accomplish the same thing for as long as I hold the shutter.

[Waddizzle]

“…. I get it that it's an Auto ISO issue, but this does not occur if I set the focus to One Shot. …”

How did you come to that conclusion?  You have not stated which AF points, what Exposure Mode, which Shooting Mode, or which lens that you are using.  The devil is in the details.

[kevinbarre]

I said that it was in Aperture priority. I said that it only occurred when set to Servo focus. Failed to mention face detection—so ALL focus points. It does not occur when I have One Shot focus, on Spot, using the center AF point. 

[Waddizzle]

I did not bother to read the entire post.  Way too many unknowns are in play here.  What lens are you using?  [Full stop].  What metering mode are you using?

Are you panning, or is the shot static? Your number one problem is allowing the camera to control more than one leg of the Exposure Triangle at the same time.

[kevinbarre]

Maybe it would be helpful if you did read my full post. I previously mentioned that I was using Center-weighted Average metering while shooting a "static subject in static light."

It happens with my Canon 50/1.2, Canon 85/1.2, Sigma 35/1.4 Art, Sigma 24-70/2.8 Art—all of my lenses. All mounted with the Canon Control Ring Mount Adapter EF-EOS R.

Literally the only change that occurs in settings between it locking exposure correctly and bouncing up after two shots is the focus servo mode.

I use Aperture Priority and Auto ISO as I'm a high-paced wedding shooter who frequently works in drastically changing light conditions, utilizing the wheel to dial in +/- exposure on the go. Using these exact settings with 5DII, 5DIV, and 6D bodies all work as expected. It's only on the R6 with High Speed Continuous and Servo focus that I'm having the issue.

I get it—you're a Legend here—but I would expect you to at least read my post in its entirety before telling me there are too many unknowns in play. I'm a 30-year wedding pro who shoots 450k+ images a year. I'm no newbie. I've eliminated just about every variable I can think of.

[Waddizzle]

I think your issue is with Center Weighted Average metering mode, which will always use the area around center AF point to meter the scene. I recommend that you use Evaluative Metering, and make sure that you have an active, locked AF point when the shutter fires.

[kevinbarre]

I tried it using Evaluative Metering—still happens. I've already established that it goes away when I use a locked AF point. Specifically, I'm trying to figure out why it's happening in Servo mode—which, to be frank—is the raison d'être for the R6. 

[Waddizzle]

One Shot AF locks exposure when focus is locked, which usually occurs before the shutter fires..  AI Servo also locks exposure when focus is locked, which usually occurs when the shutter fires.

Again, use Evaluative Metering.  Most the rationale people offer up for using another metering mode are actually very good reasons to use Evaluative Metering mode.  

Evaluative Metering locks exposure at the locked AF point.  Every other mode will lock exposure relative to the center AF point.  In other words, you are focusing here and metering over there.

[kevinbarre]

Just tried it—again—using Evaluative, since you were so insistent. Still happens.

Simple shot of my desk. No moving subject, no changing light.

Frame 1: 1/250 F2.5 ISO 1250

Frame 2: 1/250 F2.5 ISO 1250

Frame 3 (and all subsequent frames): 1/320 F2.5 ISO 4000

[Waddizzle]

“What exposure mode are you using?”   I wanted to know what rationale you had for using Center Weighted Average when you are not using the Center AF point(s).

What frame rates are you using?  You say “high speed” continuous, but how fast are you using?  None of your lenses can focus much faster than 10-12 fps, if that fast.  EF lenses have limits.

Have you used DPP or a LR plug-in to see where your locked AF point actually is when the shutter fired?  If you do not have a locked AF point in Evaluative Mode, then the metering will be similar to Center Weighted Average.