5D3 + AF assist beam = slower focus

[Carerra911]

Hello All,

While I am new on these forums I have been on the Canon Rumors Forums for a few years now, 

I really wanted to bring this too the attention of you and Canon as it is simply a highly important problem, those of you that don't know, the 5D3 suffers serious focus locking issues when a Canon speedite is attached in Low light, the AF assist beam causes lag with the AF from the 5D3, this makes it virtually impossible to achieve focus in low light when the speedlite is attached, I wanted to bring the topic to this forum, so I have pasted a link to all the discussion we have already had about this problem at Canon Rumors.com - see below

http://www.canonrumors.com/forum/index.php?topic=10275.0

Please help in letting Canon know this is a very serious problem and effects the cameras performance in most working environments when a speedlite is attached and working in low light, conferences, nightclub work, weddings etc, and can stop the photographer completing the job or task.

Regards

Louis

[Carerra911]

Some tests been done by Michael

http://www.canonrumors.com/forum/index.php?topic=11566.0

"Had several requests to measure the focusing speed of the 6D vs 5Diii vs 5Dii using a Speedlite (in this case 600ex) in low light conditions. Its a redo of the other focusing test I did this week, only this time using the red-af assist light. 

Target 1 Evenly exposed at 1/60, 2.8 ISO 400, about 20 feet away
Target 2 Underexposed about 7 stops with the same settings, about 4 feet away

I ran each camera through 30 focus locks back and forth. 

Interesting results:

Canon 5Dii - 45 seconds
Canon 6D - 52 seconds
Canon 5Diii - 70 seconds

 I should note 2 things: the 6D does very well even without the AF assist beam. The 6D & 5Diii both feel as if there are 2 stages of focus, a larger followed by a smaller step. The 5Dii seems to lack this. "

[dll1477]

Can you explain these test results please -- is 70 seconds the amount of time required for one exposure attempt to acheive focus?  is this the mean (average) of 30 attempts?  the sum of 30 attempts?  the median value of the 30 attempts

[digital]

Actully I have been testing the full press and I seem to be getting in focus shots. I stated seem to as I need to test this more to  be sure.

Post #23

http://www.canonrumors.com/forum/index.php?topic=11566.msg206887#msg206887

[ScottyP]

The time is the total time it took him to achieve 30 focus locks.  So the 5D3 was 2.33 seconds average per lock.   The 6D was 1.7 seconds average.  The 5D2 was 1.5 seconds.

[ScottyP]

Note this was actually an easy test. High contrast black tape on white wall. And not moving. Some say it is worse in real shooting.

[echelonphoto]

So we have been duped? All I heard about the mark 3 was how much better the af was than the mk2

[marcdegroot]

interesting results.

bench tests are no good, they need to be field tested like they should have been before they released the camera.

[Carerra911]

I agree, this should of been testing in the field, it makes you wonder if these are tested in all scenarios,  I hope for a fix,  Im not sure if its possible, and Im not sure what to do with the camera if things dont change

[MichaelTheMaven]

Hi Mike- 

I can confirm there is something strange going on with the 5Diii in low light.

I posted 2 targets, Target 1 at 20 feet (evenly exposed at 1.60, f2.8 ISO 400- I believe close to EV7), Target 2 at 4 feet underexposed 7 Stops on the same settings, and then focused back and forth 30 times with 3 different Canon bodies using a Canon 600 Ex Speedlite AF for focus assist.

Camera/Total Time through 30 focus locks (Target 1 is always faster BTW)

Canon 5Dii - 45 seconds

Canon 6D - 52 seconds

Canon 5Diii - 70 seconds

1. Im using a 24-70 2.8 L II lens, all shots were taken at 70mm

2. The underexposed Target 2 was 4 feet away, this is where it struggles.

3. Center Focus square

Michael

[MichaelTheMaven]

I should probably add a note about why I am going back and forth between the 2 differnent targets at different distances; Target 1 serves mainly to defocus. If im just aiming at target 2 and focusing over and over, its not a good measurement of the cameras ability to get that initial focus. 

Another point is that the average focus times for each shot work out to:

5Dii - 1.5s

6D - 1.7s

5Diii- 2.33s

But this is not what is happening. The focus lock on Target 1 (in good light) is always very quick, almost instantaneous. 

Focusing on Target 2 is taking longer than these average times. In fact, most of the time is spent on Target 2. 

Unless I had someone watching me with a stop watch it would be hard to know exactly (maybe we have to just video tape this whole event).

But I would say the times are closer to:

5Dii - 2.2s

6D- 2.5s

5Diii - 3.5s

I was planning on doing some more tests this weekend. If you guys want me to try something specific let me know. Ive gotten some good recommendations.

M 

PS- If it makes anyone feel better, the Nikon D600 cannot focus at all on target 2 without it's focus light on. 😉