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Auto focus points not accurate, is this normal?

674 Views 6 Replies Latest reply: May 13, 2012 7:03 PM by karbru RSS
karbru Level 1 Level 1 (0 points)
Currently Being Moderated
May 13, 2012 3:38 PM

When I turn on "show focus points" in aperture, the focus point is not accurate. For example:  I took a photo of my daughter. I focused on her right eye, and then recomposed the shot.  When I checked the focus point in aperture, the focus point was to the side of her face instead of on her eye. If I do not recompose the shot, the focus point is accurate. Is this how the focus point works in aperture?  I have a Canon S95, and the issue occurs with that camera and aperture too.  I also tried different lenses on my DSLR, and got the same results.  The photos seem to be in focus, but I would like to know if this is normal for Aperture.

Thanks for any info.

Karen

iMac, iOS 5
  • Ernie Stamper Level 8 Level 8 (37,455 points)
    Currently Being Moderated
    May 13, 2012 4:05 PM (in response to karbru)

    The info Aperture is using is being read from the meta-data from the camera.  It is accurate within the matrix of the sensor, and it not based upon the final composition of the photo, in my opinion.  I would expect nothing else.

     

    Ernie

  • dbmoore Calculating status...

    Hi Karen

     

    Ernie is right on the matrix.  I have a canon mark III and it is off in focusing.  its a tad bit closer than the sensor. My camera however is adjustable but not all are.  Cheers

  • Kirby Krieger Level 6 Level 6 (11,585 points)
    Currently Being Moderated
    May 13, 2012 5:40 PM (in response to karbru)

    This needs, I think, a little more clarification.  The "focus point" to the camera, is which of the focus points was used.  _These have a fixed relationship to the sensor_, and thus a fixed position in relation to the flat rectangular array of data that we call a photograph.

     

    Karen -- you didn't actually focus on the eye.  You focused on the data that fell under one of the focus points of your camera.  Which of the focus points is used is recorded in the metadata and displayed by Aperture.  The camera -- and, perforce, Aperture -- does not "know" whether your daughter or the camera moved or was moved between the time focus was made and the time the exposure was made.  All Aperture is telling you is which focus point was used.  If your camera or subject moves, what is in focus in your photo will not correspond to the location of the focus point used.

     

    This has _nothing_ to do with front- and back-focusing, which is what dbmoore refers to.

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