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!

[kvbarkley · Accepted solution]

Using this EV calculator:

https://www.omnicalculator.com/other/exposure

Your dark images have an EV of 14. "Good for taking photos on a bright day"

Your light images have an EV of 12-12.4 "EV ~12 is suitable for taking photos of the sunset, during sunset, and just before the sun sets." Which is a little lower than I would think for this shot.

What mode are you shooting in? The camera info shot shows Tv, but your shutter speed is varying in the sample images.

Either all the sand is fooling the camera - which used to be a big issue, or as Trevor suggests, it is your metering mode. If you are using the same mode as in the camera settings above you are using spot metering which would explain the discrepancy. Use Evaluative.

In this case, for the lower two images, the dark one is exposing on the sand between the subjects and for the light one it is exposing on the man's shirt.

[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

[stevet1]

KingBloobie,

Do you possibly have your exposure compensation bracketing turned on, by any chance?

Steve Thomas

[KingBloobie]

Thanks for the suggestion, Steve! Exposure Compensation is always set to 0. The resulting exposures vary widely from shot to shot, even if they're taken milliseconds apart. 

[kvbarkley]

Are these indoors? Could be flickering lights

Does the EXIF data concur with a "wildly varying" exposure?

Does it happen on more than one lens? It could be a sticking Aperture.

[KingBloobie]

Excellent questions! I'm gonna research them and get back to you. Thanks for taking the time to respond!

[Tronhard]

Hi and welcome to the forum:

Please excuse some, what might seem obvious, questions:
What lens or lenses do you shoot with?
Does this happen with every lens or just one?
Have you changed anything at all recently about the camera?  New card, new lens, a new or different front filter, new battery?
What kind of environment do you shoot in - indoor sports, wildlife, fashion, concert etc.?

What is the shutter count of the camera - if you have it on the default settings for numbering, which is continuous and have not reset the card numbering, or put in a card that has been used elsewhere and not formatted clean, then the number will be the file name ###-#### where 102-2658 would be the equivalent of 23,658.

Thank you

[KingBloobie]

Trevor, wow, good info. Some of it is above my pay grade, but I'll research and get answers. Your input is very much appreciated!

[KingBloobie]

While I'm doing my research to answer your suggestions, here are a couple of recent examples of the exposure variations, both variations within one second of each other. Photo info is included.

    

[Tronhard]

My first reaction, looking at these images is that I am confused why you are using what you describe as a 'spray and prey' technique, which is not a great technique.  It is clear that of the images you shared, some are in focus and some not, and it looks like your ISO is locked down to 100.

My first thought is that it is how the camera is being used that is the issue.  You are using Canon EF-S 18-135 STM lens, which is quite a good lens, so unless the camera or lens have been damaged, it is more likely the setting or your technique.
I would be interested to know what exposure system the camera is set to - which is different from the focusing system.  The default is Evaluative, which considers the whole visual area and averages out the exposure.  Setting the camera to high speed frame rates is not necessarily the best for this kind of social photography.   My feeling is you need to slow down and take more time to get a fewer, better images.

If you want multiple exposure, set the frame rate to a lower value and give the camera more time to do its exposure control.

Can I suggest the following as a test.
Set the ISO to Auto
Set the camera to P mode and take some photos of the same static point being careful with your focus.
check the results.
Point the camera at several different types of subject some darker, some lighter and some between.  How do they come out.

[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.