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Thread: Focus and recompose - aye or nay?

  1. #1
    The Stig's Avatar
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    Focus and recompose - aye or nay?

    I used to focus and recompose until I read somewhere (or someone told me - I can't remember) that it was a bad idea, as this shifts focus in relation to what you're shooting. As a consequence I've been using the different AF points (my camera has 11) when shooting stationary objects, and what Nikon calls Dynamic Tracking when shooting moving "targets". This has been something of a hit or miss affair, as the response is slow and sometimes erratic - especially in anything less then the midday sun.

    I understand the point about the focus shifting when you recompose after focus lock, but I'm curious as to the strength of the effect and how much of a problem it is in a real world scenario. I did a test on a close object with my 35 mm f/1.8 wide open. I was thinking that any adverse effects would be at its most visible under these conditions. I took a control photo using the sidemost AF point and a test using the focus/recompose technique. Frankly, I'm not able to see which photo is which. There is a small but noticeable difference in focus between the two images, but nothing that screams focus error. Besides, it's not like one image is drastically better then the other. Both photos are sharp with a shallow DOF, but a little bit different if you zoom in at 100 %.

    Should I just stop worrying and go out and take some pictures, or is there a less forgiving scenario I could try out that highlights the weakness of this approach?

    A Norwegian krone for your thoughts, ladies and gentlemen.

    Cheers,

  2. #2
    abhi's Avatar
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    Re: Focus and recompose - aye or nay?

    Hi Stig,

    I think you can use either approach. I personally use the AF points unless the light is low, in which case I have trouble focusing with any but the one in the center. If you focus and recompose, just try to move parallel to the plane of focus and the focus will stay the same. If in doubt, use the DOF preview button! Hope this helps. I am sure more informed and detailed opinions would soon follow

  3. #3
    jiro's Avatar
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    Willie or Jiro is fine by me.

    Re: Focus and recompose - aye or nay?

    I use an old DSLR, namely the Nikon D70. There's only a cross-type focus sensor on it and that is the one at the center. 5 focus sensors all in all 2 vertical on each side and 2 horizontal on the top and bottom. The best option for me would be to use the cross-type sensor at the middle so I aim and recompose 98% of the time. The remaining 2%?... when I am in continuous shooting mode and I have no idea when will the shutter release its hold and take the shot. Check your camera's manual and see where does the cross-type sensors are located and use it to your advantage, Stig. One more thing, try to spend more time knowing how your camera works on all focusing mode so you'll know what to use in every unique scenario. Hope this helps.

  4. #4
    Black Pearl's Avatar
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    Re: Focus and recompose - aye or nay?

    It tends to be a problem with very fast aperture lenses and longer ones at that where the DoF is tiny and small differences will have a dramatic effect on the sharpness.

    Your 35mm might just show it. Focus on a subjects eye with the eye in the middle of the shot - now re-frame so the eye is near the edge of the frame and take the shot. I think it should show the shift you have read about with the eye now being a little beyond the point of focus.

  5. #5
    Letrow's Avatar
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    Re: Focus and recompose - aye or nay?

    It would also show up of course in macro work, where DOF is limited anyway. My guess is that you don't do that and with a 35mm lens and subjects a few metres away you should be fine I assume.

  6. #6

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    Re: Focus and recompose - aye or nay?

    I've been known to use my auto focus lock button on a recomposure. As long as I don't move radically from the original plane or distance, I find it to hold true. If I do move, it takes but a millisecond to refocus. I think after seeing that both you and Rob use the 105 macro, that's my next move...though, I am now thinking Tokina as I understand they make the Nikkor lens for Nikon.

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