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Author Topic: Autofocus in AI-Servo performance in low light  (Read 1100 times)


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Autofocus in AI-Servo performance in low light
« on: February 09, 2013, 04:36:46 PM »
So this half-way goes here, half-way goes in the 3rd party lenses section, but I figure this section gets more traffic.

As my post subject implies, I'm looking for some information on the Autofocus performance in AI-Servo, specifically on a 5d3, of 24-70 f/2.8 lenses. I've been highly tempted to get the Tamron 24-70 f/2.8 VC because of the lower price than the Canon v2, pretty good sharpness/IQ, and image stabilization. Just rented it for the second time, and in very poor lighting conditions both times. Most of the time it was doing just fine, getting decent to good focus, but there were quite a number of times when it just wasn't getting the focus. I was using Case 6, as this was a dance performance.

As I said, it was very poor lighting conditions, and I've attached a sample image where it didn't follow them and keep them in focus. I checked in DPP, and no AF point had focus, and the shots immediately preceding this one were a bit wider, and it was actually 5 shots previously that was the last time it had focus lock. I was in Zone, and with the center 9 AF points as the active points. Most of the time I had the AF running, even if not actually taking a photo.

So, anyone using the Canon 24-70 f/2.8 v2 or other 24-70 f/2.8 lenses that has been using it it for something similar, with difficult lighting, very active subjects? I'm trying to determine if it's more the Tamron lens than my 5d3, or if the Tamron is not able to keep up with the 5d3. I am thinking I'll rent the Canon v2 for the next performance in April, which will likely have pretty similar lighting, so I'll be able to test it in pretty similar conditions.
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Re: Autofocus in AI-Servo performance in low light
« Reply #1 on: February 09, 2013, 07:46:17 PM »
Do not use AI Servo in low light 
It has little to do with the lens.  Its very difficult for a camera to find focus in low light and takes a second or two.  No way can it AF continuously in very low light.
Just use one shot and center point if the light is very low.