5D Mark III Sometimes Not Allow Me to Shoot

My 5D Mark III sometimes do not "allow" me to shoot. I press the shutter release but it would not take the shot, ... no click.

It happens mostly with the 24-105mm f4L but happens less frequently with the 70-200mm f2.8L IS (ver 1). Sometimes if I waited 15-20 seconds, or point the lens towards the ground for a couple of seconds and return aim to the subject it would take the shot and a few more. The battery charge is not an issue, it is full or quite full in these instances. Also, this happens after I upgraded FW to 1.2.1

Not sure why, what are some of the settings I should check?

Are you getting focus confirmation?

On AF only? If so, likely not seeing enough light/contrast to achieve focus. In the viewfinder the should be a blinking icon on the far right indicating an AF problem.

Andy may be right. If you are closer to the subject than the Minimum Focusing Distace for your lens, the camera will not focus and not let you take the shot. That is one possible reason for your issue, but in general if you do not get a focus lock (dot in the viewfinder and/or beep tone), the camera will not trip the shutter.

Thanks everyone. I will check my AF so see if I get a lock.

Is it buffering? I know if I use my SD card, instead of my CF, it's crazy slow, and it will not fire.

UKseagull wrote in post #15991204
Are you getting focus confirmation?

This is my first question.

Too close? Too dark? Lack of contrast for AF to lock on? Any of these will cause the AF to not lock, hence no shot.

Next time it happens, switch from One Shot AF to Servo AF. Servo will let you take a photo even if there is no focus lock.

I've had the same thing on mine and I think you might have got it set on Focus Priority on the second pink menu setting. It makes the camera attain focus before it allows the shot to fire which has stopped me a few times from getting the shot but if the shot was blurred anyway what would be the point.

Thanks everyone. Mine is already on AI Servo.

As for the Pink Menu: on the second menu, I've set both to "equal priority" ,on the third menu: I've set the One-Shot AF release prior to "Release". Yes, I am aware that I might get more OOF shots as a result of this change. But I've missed so many shots -- even ones that were fairly well-focussed as a result of having it set to "Focus".

"It happens mostly with the 24-105mm f4L but happens less frequently with the 70-200mm f2.8L."

Significant difference in lighting levels. Bump the ISO up and see if the issue diminish.

The handful of times it's happened to me is it was simply too dark to get focus. I don't recall if I bumped the ISO or simply moved closer to the subject to get better lighting. Typically, I shoot with the 24-105 f4L, but other times with an 80-200 f2.8L. Never had the problem with the 135 f2L, though. Bottom line...it's all about light.

John from PA wrote in post #15993190
"It happens mostly with the 24-105mm f4L but happens less frequently with the 70-200mm f2.8L."

Significant difference in lighting levels. Bump the ISO up and see if the issue diminish.

bratkinson wrote in post #15997904
The handful of times it's happened to me is it was simply too dark to get focus. I don't recall if I bumped the ISO or simply moved closer to the subject to get better lighting. Typically, I shoot with the 24-105 f4L, but other times with an 80-200 f2.8L. Never had the problem with the 135 f2L, though. Bottom line...it's all about light.

I'm struggling with the concept of higher ISO improving AF performance - I don't believe it can. Can you explain this to me please?

I don't think increasing the ISO will help. That only increases sensor sensitivity, not the amount of light the phase detect AF sensors can "see". The only way i can see that could help is if one is using live view AF which uses the sensor.

JohnB57 wrote in post #15997946
I'm struggling with the concept of higher ISO improving AF performance - I don't believe it can. Can you explain this to me please?

+1 to this.