Indoor pictures intermittently dark

[annhackler]

I have a T6i that is just over a year old.  I shoot inside in normal room light often, using the auto setting.  Recently the shots are intermittently dark and the level of darkness varies.  Sometimes you can barely tell there is any image, other times you can make it out.   When it starts happening, there will be maybe three dark shots in a row then all of a sudden a perfectly lit shot.

[diverhank]

Wow...there is not enough data in your description to do more than hazarding a guess but I'll do it anyways.  Since you described that everything used to work fine and now sometimes the pictures are too dark and sometimes perfect and your flash is also acting up...like buzzing and flashing in burst...

What mode are you shooting with?  Is it the green square or P when you mentioned Auto?

My wild guess would be that somehow you have inadvertently set your ISO from Auto to a fixed setting.  The camera sets itself to the correct lighting conditions by varying 3 things: speed, aperture and ISO.  With Auto ISO, the camera will auto adjust to the varying conditions using all 3 things and for something modern like a T6i, it can handle most of the lighting conditions.  If you set the ISO to a fixed value...the auto mode can only adjust 2 things: the speed and aperture to a certain values and the camera would literally runs out of light without being able to vary the ISO.  That might explain why sometimes your pictures are too dark and then OK (depending on available light).  When the camera runs out of light. one problem would be trying to focus by using the flash as the focus assist...

First thing you should check is to see the ISO is not set to Auto.  As I said, this is a wild guess.

[Waddizzle]

It sounds like flickering indoor lighting to me.  The flicker is normal, and too fast for the human eye to see.

[ScottyP]

I think either:

1.). Wadizzle is right and you have flickering fluorescent lights fooling the cameras meter, or

2.). Your well lit shots are with flash and the dark ones were taken without the flash firing, before the flash could charge or recharge up. 

Does it it happen outside in sunlight or only indoors?  Does it happen indoors in other places with different lights or just in the one house?

[annhackler]

Thanks so much for getting back to me so quickly. I'll be checking this out tonight!

[annhackler]

Thanks so much, will be checking this out tonight. We did just replace all our bulbs this year with LEDs, though it is happening in the house as well where we did not do that. (I am shooting in a barn) I'll let you know what I find out later. Thanks again.

[Waddizzle]

---

@annhackler wrote:
Thanks so much, will be checking this out tonight. We did just replace all our bulbs this year with LEDs, though it is happening in the house as well where we did not do that. (I am shooting in a barn) I'll let you know what I find out later. Thanks again.

---

Solid state lighting, like LEDs, flickers too fast for the eye to see, but the speed of a camera shutter can.  Some of the high end Canon cameras have smarts built into them to detect flickering light sources and time the shutter being released for an exposure at the highest light output.

[annhackler]

The problem only happens inside. And it only happens when the flash is supposed to be working--to compensate I have been shooting either in "sports" or with the "flash off" setting inside. Diver hank suggested that the problem might be that I had moved the ISO to a fixed setting from auto and he is right, I did do that. I've moved the ISO back to auto, so I'll see if that solves the problem.  But I more often than not shoot in Intelligent Scene Auto--so there is no option on the ISO---and the problem remains.  It seems that about every third shot is dark.

[annhackler]

I did have a fixed setting in the P setting, so I switched that.  But normally I am shooting in Scene Intelligent Auto.  It's almost as if the flash is firing late sometimes.  

[diverhank · Accepted solution]

---

@annhackler wrote:

The problem only happens inside. And it only happens when the flash is supposed to be working--to compensate I have been shooting either in "sports" or with the "flash off" setting inside. Diver hank suggested that the problem might be that I had moved the ISO to a fixed setting from auto and he is right, I did do that. I've moved the ISO back to auto, so I'll see if that solves the problem.  But I more often than not shoot in Intelligent Scene Auto--so there is no option on the ISO---and the problem remains.  It seems that about every third shot is dark.

---

As others have suggested, there is a high possibility that you are under the flickering effect of the LED lights.  Luckily the T6i has the "Anti-Flickering" option so you should activate that.  While there is no guarantee that it will fix the problem, it will 1. lessen it and 2. it will tell you that there's a flickering problem (FLICKER! is shown on the viewfinder).