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Thread started 03 Jul 2010 (Saturday) 12:16
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50D & Ai Servo - my 1st attempt

 
lensmen
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Jul 03, 2010 12:16 |  #1

I tried the Ai Servo today, using the 70-300 USM tracking after eagles over the seaside, in good afternoon light. The focus was set to center point only.

Seems that when I looked thru the photos on the big screen, it appears to have missed the focus by about 60%. The composition and time was acceptable, but that minor OOF is enough for me to delete the shots.

It is my 1st time relying on this mode. Perhaps I misunderstood how to use it ?

Appreciate feedback


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James ­ Wheeler
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Jul 03, 2010 13:47 |  #2

The 70-300 is known to be soft at the 300 end, try bringing it back a little to like, 290 or something. Or, use your 100-400 :)

Did you have the shutter speed high enough?


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mnaz
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Jul 03, 2010 14:16 as a reply to  @ James Wheeler's post |  #3

Also did you move your focus to one of your back buttons? I couldn't imagine trying to track something in servo using the shutter button.


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James ­ Wheeler
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Jul 04, 2010 03:23 |  #4

mnaz wrote in post #10472038 (external link)
Also did you move your focus to one of your back buttons? I couldn't imagine trying to track something in servo using the shutter button.

What a poor imagination you have... :) It really is no leap of conciousness.

I am trying the back button focusing for the first time and am undecided on it. The advantages it supplies don't seem to outweigh the disadvantages for me so far (less steady grip of camera) but I am trying it for longer so I can get used to it.


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apersson850
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Jul 04, 2010 04:36 as a reply to  @ James Wheeler's post |  #5

I hold the camera just as steady, since my thumb is very close to the AF-ON button anyway.
The advantage of the rear button focus isn't that much obvious when tracking birds. At least if they aren't too low down, there are no obstructions by bushes between you and the bird and so on.
When tracking things moving on the ground that happens much more often, and then the advantage of AF-ON for focus is that you can stop focusing but continue shooting, since the trigger doesn't focus.

But something up in the air you can just keep tracking.


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tom ­ s
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Jul 04, 2010 14:11 |  #6

70-300 f/4-5.6 has micromotor USM, not the real USM.
With real USM there's no problem.


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Jul 05, 2010 09:00 |  #7

apersson850 wrote in post #10474530 (external link)
I hold the camera just as steady, since my thumb is very close to the AF-ON button anyway.
The advantage of the rear button focus isn't that much obvious when tracking birds. At least if they aren't too low down, there are no obstructions by bushes between you and the bird and so on.
When tracking things moving on the ground that happens much more often, and then the advantage of AF-ON for focus is that you can stop focusing but continue shooting, since the trigger doesn't focus.

But something up in the air you can just keep tracking.

Do you use C.Fn-IV-I-2 or C.Fn-IV-I-3?


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Jul 05, 2010 09:33 as a reply to  @ pfpeter's post |  #8

On the 7D, it's C.Fn IV-1 which controls all assignments of functions to buttons.

For action, I set it like this:

  • Single point AF with expansion.
  • Servo AF.
  • Joystick to immediately move start point for AF.
  • Metering: Center weighted if using AE, otherwise partial.
  • Trigger button: Metering only
  • AF-ON: Focusing while pressed on selected AF point.
  • *: Focusing while pressed on registered (HP) AF point.
  • Orientation dependent AF point selection. This is true for the HP as well.
  • M-Fn: AE lock, should that be needed.
  • DOF preview: Modifications to AF tracking and interference handling, plus siwtch to Zone AF, if the subject comes too close to handle well with single point expanded AF.
To use automatic exposure or manual is something I decide upon depending upon the conditions. My subjects are usually on the ground, among bushes, trees, other people, shadows and sunlit areas, so both focusing and exposure is sometimes a bit too variable to be easy to handle...
The Home Point I store so that it's high up in the image. Thus I can always focus on a face, if I want to, by just using the * button instead of the AF-ON. The main point is often in the center, but I move it around as needed. These setups I store under the C1 and C2 locations on the mode dial. Very handy.

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lensmen
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Jul 05, 2010 10:23 |  #9

James Wheeler wrote in post #10471936 (external link)
The 70-300 is known to be soft at the 300 end, try bringing it back a little to like, 290 or something. Or, use your 100-400 :)

Did you have the shutter speed high enough?

The shutter was OK BUT the minor OOF is really irriating.


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lensmen
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Jul 05, 2010 10:26 |  #10

mnaz wrote in post #10472038 (external link)
Also did you move your focus to one of your back buttons? I couldn't imagine trying to track something in servo using the shutter button.

Huh ? Please tell me how to do this ?

I still do not understand the concept of this Ai Servo & Ai Focus.

Was it supposed to lock on the subject, and then track it continuously ? By the 1/2 press of the shutter button.


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Rubi ­ Jane
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Jul 05, 2010 10:30 |  #11

What was your aperture, did you have sufficient DOF.
Post a couple of examples of missed focus and acceptable focus.


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lensmen
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Jul 05, 2010 10:35 |  #12

tom s wrote in post #10476380 (external link)
70-300 f/4-5.6 has micromotor USM, not the real USM. With real USM there's no problem.

I had tried the Ai Focus with the 100-400mm L yesterday @ the airport on a blue skies Sunday.

http://www.facebook.co​m …id=725286714&l=​12b5240003 (external link)

There are a few times that I switched back to One-Shot mode as I could see that it was a minor OOF ! Somehow, most of the shots were ok on the big planes but it flatened my 2 batteries on the grip within the hour ! Wah....whats happening ? Is the Ai Servo working all the time, although I haven't 1/2 press the shutter button ?


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Genome
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Jul 05, 2010 10:38 |  #13

AI Servo tracks what is over your selected focus point. So if you are following birds in flight and using the centre point then make sure you keep a point of contrast of the bird over the centre point while half pressing the shutter (unless you use back button focusing in which case you hold that button instead) Its a good idea to let it track for a second or 2 before shooting to let it get its focus. It doesnt have a lock confirmation you see so its constantly adjusting. You should be able to get a decent keeper rate but the lens is an important factor as well. Some lenses focus a lot faster and more accurately than others.

Ai Focus mode is a combination of Si servo and single shot. It works as single shot does but if it detects the subject is moving it switches to Ai Servo type focusing. Personally i dont use it. I stick to single shot and servo modes.


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Jul 05, 2010 11:10 |  #14

Rubi Jane wrote in post #10480086 (external link)
What was your aperture, did you have sufficient DOF.
Post a couple of examples of missed focus and acceptable focus.

Shutter speed is about 1/500 and f stop about f7.1 range, shooting at P mode, auto ISO & cloudy WB

The photo album is here :

http://www.facebook.co​m …id=725286714&l=​eb69c69532 (external link)


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lensmen
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Jul 05, 2010 11:13 |  #15

Thanks Genome.

@ Ai Servo mode, is it possible to have the option of both the 1/2 shutter button & AF-ON button to activate this ?

I was hoping that the AF-ON can be pressed to tell the camera to instantly refocus at the focus point. Can this be done ?

I'd like to practice a lot on this. The camera has it and I should learn to use it more often.

Genome wrote in post #10480122 (external link)
AI Servo tracks what is over your selected focus point. So if you are following birds in flight and using the centre point then make sure you keep a point of contrast of the bird over the centre point while half pressing the shutter (unless you use back button focusing in which case you hold that button instead) Its a good idea to let it track for a second or 2 before shooting to let it get its focus. It doesnt have a lock confirmation you see so its constantly adjusting. You should be able to get a decent keeper rate but the lens is an important factor as well. Some lenses focus a lot faster and more accurately than others.

Ai Focus mode is a combination of Si servo and single shot. It works as single shot does but if it detects the subject is moving it switches to Ai Servo type focusing. Personally i dont use it. I stick to single shot and servo modes.


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50D & Ai Servo - my 1st attempt
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