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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 24 Jan 2013 (Thursday) 02:08
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AI Focus question

 
Plumtreelad
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Jan 24, 2013 02:08 |  #1

I have been using AI focus for almost a year now when shooting sports photography (field hockey) and after all this time I have a basic question that I need an answer to. I shoot a 7D and a 5DmkIII with a 300m 2.8IS. Shutter speeds are always at least 1/800 and more usually 1/1000. Aperture when indoors is 2.8 but narrower when outdoors. I use a monopod.

My keeper rate is not very high because I do not always get pin sharp images that I am seeking.

The question is this. With AI servo is it still better to keep the camera still when taking shots rather than move it as you follow the play? If the shutter speed is 1/1000 I would not have thought that camera movement would have any impact on sharpness - but I would like that confirming.


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Jan 24, 2013 03:37 |  #2

Plumtreelad wrote in post #15527117 (external link)
I have been using AI focus for almost a year now when shooting sports photography (field hockey) and after all this time I have a basic question that I need an answer to. I shoot a 7D and a 5DmkIII with a 300m 2.8IS. Shutter speeds are always at least 1/800 and more usually 1/1000. Aperture when indoors is 2.8 but narrower when outdoors. I use a monopod.

My keeper rate is not very high because I do not always get pin sharp images that I am seeking.

The question is this. With AI servo is it still better to keep the camera still when taking shots rather than move it as you follow the play? If the shutter speed is 1/1000 I would not have thought that camera movement would have any impact on sharpness - but I would like that confirming.

Images from an outdoor sport that resembles field hockey.

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
Byte size: ZERO | Content warning: NOT AN IMAGE

Focal Length: 110.0mm
Aperture: f/5.6
Exposure Time: 0.0003 s (1/3200)
ISO equiv: 800
Exposure Bias: none
Metering Mode: Matrix
Exposure: shutter priority (semi-auto)
White Balance: Auto
Flash Fired: No (enforced)
Orientation: Normal
Color Space: sRGB

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
Byte size: ZERO | Content warning: NOT AN IMAGE


Focal Length: 130.0mm
Aperture: f/6.3
Exposure Time: 0.0003 s (1/3200)
ISO equiv: 1250
Exposure Bias: none
Metering Mode: Matrix
Exposure: shutter priority (semi-auto)
White Balance: Auto
Flash Fired: No (enforced)
Orientation: Normal
Color Space: sRGB

IMAGE NOT FOUND
IMAGE IS A REDIRECT OR MISSING!
Byte size: ZERO | Content warning: NOT AN IMAGE


Focal Length: 140.0mm
Aperture: f/6.3
Exposure Time: 0.0003 s (1/3200)
ISO equiv: 1600
Exposure Bias: none
Metering Mode: Matrix
Exposure: shutter priority (semi-auto)
White Balance: Auto
Flash Fired: No (enforced)
Orientation: Normal
Color Space: sRGB

One solution is not aperture or camera movement or focus mode, it's shutter speed. The quicker the action and the greater the need to stop motion, the faster the shutter speed will need to be. For some cameras, which often have a 1/4000 minimum. it may take the fastest shutter speed available.

If a sport's action moves, then the camera must move to track that motion. Accurate and decisive tracking can minimize motion blur. However, sometimes that blur can not be eliminated. It's part of action photography. That's one reason to expose several frames in sequence for each play, to improve the chances of getting one useful frame in a dynamic and uncontrollable situation.



  
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Kolor-Pikker
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Jan 24, 2013 03:37 |  #3

AI focus or AI servo? AI focus is that mode which automatically switches between One Shot and AI Servo automatically... I don't really use it, because if I want tracking I just set the camera to plain AI Servo and be done with it, it's accurate enough for single-shot purposes if the subject isn't moving, so I don't use other modes as much.

Obviously you should always follow the vector of the action as you shoot regardless, you can get away with lower acceptable shutter speeds, and if you're good enough, you can get some directional blur in the shot for effect. Personally I'm not a huge fan of freezing action with very high shutter speeds. YMMV.


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tonylong
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Jan 24, 2013 04:45 |  #4

Your shutter speed should be high enough. Spend some time shooting in AI Servo, keeping your shutter button pressed half-way, and see how your "keeper rate" goes.


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Kolor-Pikker
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Jan 24, 2013 05:36 |  #5

IMO, servo works best with back-button focus, with the AF-ON button working the focus. This allows you to continually focus, whether or not you're ready to take a shot or burst, half-depressing the shutter isn't always comfortable. Just saying.


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PhotosGuy
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Jan 24, 2013 09:28 |  #6

tonylong wrote in post #15527282 (external link)
Your shutter speed should be high enough. Spend some time shooting in AI Servo, keeping your shutter button pressed half-way, and see how your "keeper rate" goes.

I agree. I can't remember how long it's been since I last used AI Focus.

The question is this. With AI servo is it still better to keep the camera still when taking shots rather than move it as you follow the play?

NO! This is what AI Servo is made for!

If the shutter speed is 1/1000 I would not have thought that camera movement would have any impact on sharpness - but I would like that confirming.

There will be some impact on sharpness. It's just so small that you don't see it at 1/1000 sec. To some degree, this is what's happening as the shutter moves across the frame: "Pre-Cruise" at 1/15 seconds - 7/28/12

And I agree with Kolor-Pikker about not freezing everything in the frame. (Obviously!) ; )


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Plumtreelad
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Jan 24, 2013 17:07 |  #7

Kolor-Pikker wrote in post #15527208 (external link)
Personally I'm not a huge fan of freezing action with very high shutter speeds. YMMV.

But you would still want the main subject to be in sharp focus or am I expecting too much from a fast moving sport. Many of the sports images I see are very crisp and to me that suggests they are using fast shutter speeds that do freeze the action. So the question is "to freeze or not to freeze" and I suspect that there is no right or wrong answer.


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chauncey
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Jan 24, 2013 18:40 as a reply to  @ Plumtreelad's post |  #8

"to freeze or not to freeze"

Cranking up the shutter speed is a better way to get the entire scene crisp and is realively easy, while on the other hand, panning is more artistically correct and is waay more difficult to achieve. ;)


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AI Focus question
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