Weird Variable Exposure Problems with Canon T3i

[KingBloobie]

I’ve been sucessfully using my Canon T3i for years in Shutter Priority or Program mode, with single-point focus. Recently, the exposure has varied wildly when I’m taking multiple shots at once (“spray and pray”). Any idea as to how to fix this? Thank you!

[stevet1 · Accepted solution]

KingBloobie,

You have provided 4 photos. For convenience sake, I am going to number these pictures, 1,2,3, and 4 running from top to bottom.

Pictures 1 and 2 are taken within the same time frame, and pictures 3 and are also taken within close proximity to each other, but from a different time frame.

According to the little box of information you provided with each picture, Picture# 1 has an aperture of f/8 and a shutter speed of 1/250th of a second. Because of the smaller aperture, and the faster shutter speed, this will result in a darker picture.

Picture# 2 has an aperture of f/5.6 and a shutter speed of 1/125th of a second. With a wider aperture letting in more light, and the sensor being exposed to that light for a longer period of time, this will result in a brighter picture.

Since pictures 1 and 2 were taken within 1 second of each other, that is too short a period of time for you to have made any adjustments manually. This means you have must have been in P (or Program) mode.

The same situation exists for photos 3 and 4.

In the little information box, across from the camera model, it shows a little WB icon. I think that is White Balance, and it might indicate a Cloudy White Balance. Next to it is a little black dot, and I suspect that, as others have suggested, you have been in Spot Metering.

If you have been using a Program Shooting Mode, and Spot Metering, your camera is going to set an exposure almost instantaneously at whatever that center point is aimed at.

As others have suggested, you might try putting your camera in Evaluative Metering. This will meter off your whole frame, and not just one tiny area.

Just for the heck of it, try putting your camera in Av (or aperture priority) mode and use Auto ISO for the time being. Pick an Aperture that will satisfy your depth of field requirements, like f/7.1 or f/8, and let your camera pick your shutter speed. With people walking this slowly, it shouldn't have any trouble keeping up.

There is no need to "spray and pray". Slow down and take your time. I think you'll be happier with your results.

Steve Thomas

[KingBloobie]

KVBarkley, your advice struck me as the best (and easiest for me to understand) hypothesis for solving my problem. And lo, when I went into my settings I discovered that the metering mode was indeed on Spot metering. I've changed it to Evaluative – I'm looking forward to testing your idea and hopefully turning it into THE SOLUTION!

Considering that the camera was also set on single-point focus with continuous shooting, it now seems like a recipe for the exposure problem I've been experiencing. (Weird, though, that I've been shooting like this for over a decade without experiencing this issue.) Thank you and the others who took the time to offer me help; I never expected such a generous response. I'll return here with my results...

[KingBloobie]

Tronhard, thanks for your advice! I think the Evaluative exposure setting might be the solution (I had it set on Spot metering). I'll report back here with the results. 

I wasn't able to get a shutter count on my T3i, even with the EOS app on my Mac. But I'm guessing it's about 20,000.

Re: my highly sophisticated "spray and pray" technique, I work with a state senator, a mayor and city councilmembers, often in situations that are spontaneous and unpredictable. The subjects are usually absorbed in their activities and not playing to the camera. So to maximize the odds of getting a decent shot with everyone looking respectable, I resort to that rapid-fire method.

[KingBloobie]

Steve, thanks for your input! I'm currently testing out the Spot vs. Evaluative metering hypothesis, which I'm somewhat optimistic about. I'll report back here.

[KingBloobie · Accepted solution]

Thank you all for your input! Evaluative metering saved the day. (It's always like "duh!" after you find out the solution!)