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    Default Any tips on focusing?

    When I am shooting behind the court, I find that the net always gets in the way. The lens would focus on the net (the nearer object) rather than the players on the opposite side. Believe I am focusing incorrectly. Do you guys encounter the same problem as I do? Where should I aim then?
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    Is this the full photo or cropped?

    What AF mode?

    What focussing point do you use?

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    Administrator kwun's Avatar
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    the camera naturally look for contrasty objects to focus on. on the image example above, if your focus point is on the yellow shirt, going through the net, the camera will try to focus on the net because it has more contrast compared to the shirt.

    the solution is to put the focus point on part of the player which has more contrast, the face is a good candidate, or the border between the yellow shirt and the black short.

    however, camera AF are not perfect, sometimes they do miss focus.

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    Regular Member ctjcad's Avatar
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    Default Just want to add..

    ...in the Canon 40D, the camera i assume you were using, there are a few options for the AF. If i remember correctly, there are 3 types of AF mode; the ONE SHOT, AI FOCUS and AI SERVO. What you want to try to use, esp. for baddy pics, is either the AI FOCUS or the AI SERVO mode, esp. when shooting through the net. Basically, with the AI SERVO mode you'll be able to focus on your moving subjects and the subjects will be focused continuously, while you hold down the shutter button (halfway). With the AI FOCUS mode, the AF switches from the One Shot AF to AI SERVO AF.
    *More info should be in the manual.
    Of course, as mentioned by kwun, you want to pick the an area with more contrast, initially.

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    Quote Originally Posted by Cheung View Post
    Is this the full photo or cropped?

    What AF mode?

    What focussing point do you use?
    Its a cropped photo and the AF mode is One Shot. I believe I aimed at Nasir's face.

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    guys, many thanks for the advice!

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    Quote Originally Posted by Sealman View Post
    Its a cropped photo and the AF mode is One Shot. I believe I aimed at Nasir's face.
    Can you show the uncropped photo?

    How many AF points is your camera set to?

    We can give a full diagnosis once we got that explanation.

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    Regular Member ctjcad's Avatar
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    Default ^^Just like an MD...^^

    ...full diagnosis once everything is laid out...

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    Administrator kwun's Avatar
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    2 points.

    - the actual size of the focus sensor is larger than the little red box shown on the viewfinder. so give it a bit more space.

    - i noticed a few of your photos have mis-focused. i don't know if that is operating error or maybe the sensor/lens needs to be calibrated. i suggest doing a static focus test to check it out. i usually use a tripod, and then focus on flat paper with a pattern on it. everything should come out tack sharp if the focus is accurate.

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    I also noticed quite a few of Sealman's photos off focus. Once we get the uncropped photo, we can be pretty sure of the problem.

    Forgot to ask, what lens was used for this shot?

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    Administrator kwun's Avatar
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    Quote Originally Posted by Cheung View Post
    I also noticed quite a few of Sealman's photos off focus. Once we get the uncropped photo, we can be pretty sure of the problem.

    Forgot to ask, what lens was used for this shot?
    70-200/2.8IS:



    did you have IS turned on? were you panning a lot when you took the photo?

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    yeah IS was turned on... no panning

    ps. hmm isnt that uncle loh's photo?
    Last edited by Sealman; 06-19-2008 at 05:47 AM.

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    Quote Originally Posted by Cheung View Post
    I also noticed quite a few of Sealman's photos off focus. Once we get the uncropped photo, we can be pretty sure of the problem.
    I attach below two uncropped photos for your diagnosis:
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    Thansk for the photos.

    Three possibilities:

    1) You have the AF on 9 points. If so, it will focus on anywhere that an AF point can go. The highest contrast is the net so for these two pictures, you got the net. Solved by picking a single AF point.

    2) If you have the AF on centre single point, the AF point has overlapped with the net and the AF focuses on the top of the net (that's the highest contrast point). When you look through the camera viewfinder, the AF red dot area is actually larger. Solve by zooming closer - the top of the net will not be so close to the person's face in the viewfinder.

    3) If you are one shot mode, the camera picks up focus on thet net, then you move reframe the shot because teh subject has moved. But, the AF is already locked on the net. Solved by using AF-servo.

    For both your pictures, the key person in the image is a bit small and low contrast so the AF has picked on the net.

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    For the above image, I did very little cropping. I use AF servo with centre point focus. Of course I want Tony's eyes in focus but you can see the top of the net is very close to his face. What I did was aim the centre AF point towards the highest contrast point which is approximately vertically below his face. i.e. I aimed at the line of the white shirt and black shorts.
    Last edited by Cheung; 06-19-2008 at 08:47 AM.

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    Cheung, many thanks for your advice.

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