Help with focusing system on 5DIII

shaylou

shaylou

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Shayne
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Hi all, I am turning to the experts for some help on using my focusing in this situation. I am shooting bumble bees in flight, well I am trying to anyway. I thought I understood my camera pretty well but I seem to be missing something here. I have my camera set like this. AI servo, back button focus (for tracking) shutter speed from 1000 - 4000, high speed shutter continuous. I have tried everything from single point af (wrong) to all 61 point af. I have tried tracking modes, (case 4 "accelerate decelerate quickly"), (case 5 erratic moving), and (case 2 ignoring possible obstacles). I have stuck with 61 points because I figure all the points need to be active in order to track. One of the problems I have come across is that while using 61 points it is hard to lock focus on the bee and not the flower. Oh, and I have stopped the lens down to try to grab more area in focus. With all that I still am not getting much luck at capturing the guys. I got a couple but the focus was not perfect at all. Can you please tell me if I am missing anything here. Also, any tips on the method of shooting would be appreciated as well. Thanks in advance.

:canon::exit:
 
gary996 said:
What lens you using?
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Is the correct question. Have a look in the camera manual and it explains which lens has which facility - not all have the same capabilities with the AF points - see page 79 onwards. Which AF mode are you using AI servo? Remember it uses the manually selected focus point first before tracking across all 61 points.

As for Cases? I've just left mine in case 1, tried the other modes and didn't really get on with them at sport so stuck to what worked for me. Would you not want Case 2, track and ignore others?
 
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in a situation like that i would try manually focusing on an area where you predict the bee is going to be and use a tripod especially if your using a macro lens like the 100mm L macro
my experience with that lens is it's not the best lens for tracking fast moving objects
 
I'll reiterate Gary's question and also ask if you have any extension tubes available?

Bob
 
I mostly use a 70-200II but have tried a 100L 2.8. as I said I am using AI servo as well. Can you please give me more detail on how this works. " remember it uses the manually selected focus points first before tracking across all 61 points".
 
The use of extension tubes wasn't a proposal to increase magnification but to limit maximum focus distance. Try sticking a short tube behind the lens, select the focus limiter for the longest option and then position yourself so that the background is just out of focus when the lens is set to infinity. The actual magnification shouldn't change if you're shooting from about the same distance.

Bob
 
Canon Bob said:
The use of extension tubes wasn't a proposal to increase magnification but to limit maximum focus distance. Try sticking a short tube behind the lens, select the focus limiter for the longest option and then position yourself so that the background is just out of focus when the lens is set to infinity. The actual magnification shouldn't change if you're shooting from about the same distance.

Bob
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I think I did something that would accomplish the same thing. I eliminated the possibility of missing focus do to depth of field by stopping down the lens. I made sure that I had a deep depth of field to keep everything in focus. Unless I'm not understanding you, this is the reason that you want me to try extension tubes.
 
Not quite Shayne. The lens will always focus wide open so it won't help at the AF stage. Putting a tube behind the lens will prevent the possibility of anything in the background ever being in focus (assuming that you follow the guideline in my previous post). You'll also be working in the area of the lens where there's less rotation (focus) per distance change.

Bob
 
Canon Bob said:
Not quite Shayne. The lens will always focus wide open so it won't help at the AF stage. Putting a tube behind the lens will prevent the possibility of anything in the background ever being in focus (assuming that you follow the guideline in my previous post). You'll also be working in the area of the lens where there's less rotation (focus) per distance change.

Bob
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I don't think I understand what you mean by the lens will always focus wide open. Do you mean that the auto focus will always lock on the closest target? If I were to put a tube on to keep anything in the background from being in focus wouldn't that be the same as opening the lens wide to produce a shallow depth of field. I think I have eliminated the issue of having to shallow of depth of field. The issue I have seems to be more of a tracking issue. I will get focus on the bee and wait for it to fly, when it does I attempt to track it while taking shots. At this point the shots of the bee in flight are seldom in focus. More often than not they are completely out of focus.
 
It doesn't matter what aperture you're shooting at, focus is achieved with the lens at maximum aperture and it stops down just before the shutter opens. When you put an extension tube behind a lens the lens will no longer focus at infinity...the whole range from minimum to infinity is compressed (MFD shortens too but that won't help you).
So stick a tube behind the lens and then set the lens to infinity and position yourself at a suitable distance so that the flower is blurred.....ie, it's beyond the "new infinity". When the bee flies in front of the flower the lens can no longer focus on the flower so the AF system has more chance of keeping your bee in focus.

Bob
 
I was thinking that with the level of equipment and my understanding of it that I should be able to get these bees in flight with a little luck. I was thinking that I must be overlooking something in my technique or setting. The last thing I was considering was adding more equipment although it is worth a try if I can't find anything else I am doing wrong.
 
A little luck will always be helpful but you can stack the odds a bit too.

Bob
 
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