5D3 vs 6D focusing in low light and wide aperture

[Kit Lens Jockey]

I found a good deal on a used 5D3 recently, and I was hoping that it would give me better focusing abilities in low light at wide apertures than my 6D. If nothing else, it's got a lot more cross points, which helps because trying to focus and re-compose when taking photos of fast action (music performances) at wide apertures (1.4) does not work well. The person I've focused on has already moved out of the depth of field if I focus and re-compose at 1.4. (For reference, I'm using a sigma 50mm 1.4 art lens. And stopping down past 1.4 isn't really an option due to the lack of light.)

I'm using one shot focus because, even though it's fast action, at least with the 6D, AI servo was always just a little too slow to keep up with people moving around to nail the focus at 1.4. It was just always hunting around and too slow to really keep up with what was going on.

Anyway, trying the 5D3 has, surprisingly, not even given me as good results as the 6D did. The 5D seems a lot more trigger happy and releases the shutter a lot faster than the 6D did, but it seems to prioritize taking the photo over actually getting the focus right. And, before anyone suggests this, I've already got the one shot AF priority set to focus priority. This makes it even more surprising that the 5D3 seems to blow the focus so much more than the 6D did. The 6D frustrated me at times because it struggled to achieve focus and release the shutter, but at least when it did get focus and take the photo, it was really in focus.

Does anyone else have any experience with autofocus performance between the two cameras? Should I give AI servo another try with the 5D3 since it's probably better at it than the 6D? Am I completely off my rocker for thinking that the 6D AF performance in these conditions is actually better than the 5D? I'm really dismayed because I thought the 5D would be the be all end all as far as autofocus goes, but after using it once, I find myself more drawn towards the way the 6D behaved.

 

[beagle100]

I found a good deal on a used 5D3 recently, and I was hoping that it would give me better focusing abilities in low light at wide apertures than my 6D. If nothing else, it's got a lot more cross points, which helps because trying to focus and re-compose when taking photos of fast action (music performances) at wide apertures (1.4) does not work well. The person I've focused on has already moved out of the depth of field if I focus and re-compose at 1.4. (For reference, I'm using a sigma 50mm 1.4 art lens. And stopping down past 1.4 isn't really an option due to the lack of light.)

I'm using one shot focus because, even though it's fast action, at least with the 6D, AI servo was always just a little too slow to keep up with people moving around to nail the focus at 1.4. It was just always hunting around and too slow to really keep up with what was going on.
Anyway, trying the 5D3 has, surprisingly, not even given me as good results as the 6D did. The 5D seems a lot more trigger happy and releases the shutter a lot faster than the 6D did, but it seems to prioritize taking the photo over actually getting the focus right. And, before anyone suggests this, I've already got the one shot AF priority set to focus priority. This makes it even more surprising that the 5D3 seems to blow the focus so much more than the 6D did. The 6D frustrated me at times because it struggled to achieve focus and release the shutter, but at least when it did get focus and take the photo, it was really in focus.
Does anyone else have any experience with autofocus performance between the two cameras? Should I give AI servo another try with the 5D3 since it's probably better at it than the 6D? Am I completely off my rocker for thinking that the 6D AF performance in these conditions is actually better than the 5D? I'm really dismayed because I thought the 5D would be the be all end all as far as autofocus goes, but after using it once, I find myself more drawn towards the way the 6D behaved.

no experience here with the cameras but if the 5D3 "blows the focus" perhaps you're better off getting a refurbished 6D

 

[Kit Lens Jockey]

As I said, I already have a 6D, but thought the 5D might give better focus speed and accuracy, not to mention the additional AF points. It does certainly seem faster, but only because it doesn't seem to be taking the time to really get the focus right. I'm just wondering if this is the same impression others have gotten that have used both cameras at low apertures.

 

[bratkinson]

Rule #1: If it moves, or is capable of moving while the shutter is open, AI SERVO...NO EXCEPTIONS! Before I learned that rule with my 60D, I had a lot of blurred human subjects that even while they were standing still, will move in the 1/60th or 1/125th second the shutter is open. I shoot almost exclusively with no flash on indoor subjects (people, mostly), and shooting at 1/125th and slower will increase your subject motion blur. My 5Diii is ALWAYS in AI SERVO mode to keep focus despite their movement before the shutter opens. The times I photograph buildings, bridges, parked cars or stopped trains is minimal, and I usually forget to switch it over to ONE SHOT.

I also keep my camera set to single, center point focus. I sometimes use focus and recompose, but usually keep my subject(s) dead center. As I wear my glasses while shooting, I end up shooting 10-15% 'too wide' on every thing due to not being close in to the eyepiece. Shooting wide gives me more latitude to recompose during post, when I have time to think about it, rather than in the heat of the moment.

As far as shooting at f1.4 goes, I often resort to the highest ISO speeds, 6400 & up, even 25,600 when needed, to keep shutter speed preferably at 1/250 (to absolutely freeze subject and my motion) and aperture at f4 to f5 or so for DOF considerations. Surprisingly, large JPEGs SOOC at high ISOs come out quite noise free, and saves me a lot of time editing the RAW to get the same result. Below 10000, I'll use the RAW image for editing.

Also, perform microfocus adjustment on your lenses on the 5Diii. For my lenses, after doing MF, the sharpness jumped noticeably. As most of my photos are shot from 30-50 feet away, I used a slanted ruler microfocus tool from about 40 feet away. For my zoom lenses, the 5Diii provides independent microfocusing at both ends of the zoom.

 

[goodguy]

Not a Canon guy so cant help you with the AF but if you can afford it maybe the new 5D IV, its got a new AF which is supposedly be very, very good.

 

[beagle100]

As I said, I already have a 6D, but thought the 5D might give better focus speed and accuracy, not to mention the additional AF points. It does certainly seem faster, but only because it doesn't seem to be taking the time to really get the focus right. I'm just wondering if this is the same impression others have gotten that have used both cameras at low apertures.

sure, a 5D3 and 5D4 will give you more focus points and probably speed and accuracy
an older original 1DX and /or 1Ds 3 also is better for sports or action