I have a Canon 550D ( T2i ) when on auto mode my pictures come out dark. I'm using three different lens and all are the same dark. I have an 18-55, 28-125 and a 70-300. Have to go to manual mode and play with F-stop and shutter speed. There are times when I would Just like to use auto mode but it's like the color depth gets too dark no matter what setting on the lens. I have stabilizer on and AF setting on with all lens. Pictures I'm taking are outside and without flash.
I noticed that you're using "AI FOCUS" mode. That mode doesn't work very well. Change to "ONE SHOT", and leave it there, If you're shooting moving subjects in continuous shooting drive mode, then switch to "AI SERVO" mode. Those are starting points, not hard rules. Just never use "AI FOCUS" mode.
Your posted shot wouldn't expose properly because of the light source. Can you post one of your bad photos, with the EXIF data still intact? Post one of the JPEGs that comes straight from the camera, if you can. Should we assume that the onboard flash isn't popping up, and flashing?
I deleted them, I will take some on auto mode and post them, the flash does pop up on auto mode and will change to one shot.
If you switch to "ONE SHOT" mode, the camera must lock focus before it will allow the shutter to activate. Unless you disabled the feature, the camera should beep and flash the AF point that locks focus.
If your camera doesn't beep, and lock focus, then the shutter button will refuse to take a picture. Also, note where the indicator is sitting on the exposure scale in the viewfinder.