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Curious AF failure

Discussion in 'Canon Conflab' started by PeteRob, Jan 29, 2020.

  1. PeteRob

    PeteRob Well-Known Member

    Curious one this. Discovered that the AF on my 5Ds completely fails to detect this horridly luminous lime green colour. Settles instantly on the white cord used to hang the central "heart" but as far as it is concerned the green piping itself doesn't exist. I've never come across this before. Until I experienced it I'd have thought these shapes the easiest thing in the world to focus on. No focus hunting or anything like that - just ignores them and goes to the background.

    [​IMG]274A1025.jpg by Pete, on Flickr
     
    daft_biker likes this.
  2. EightBitTony

    EightBitTony Well-Known Member

    Wonder if it works in live view?

    I don't know enough about phase detection to say if it wasn't able to separate the green from the background (which also has a lot of green?)
     
  3. Bazarchie

    Bazarchie Well-Known Member

    I will check my camera the next time I shoot luminous lime green hearts.
     
  4. PeteRob

    PeteRob Well-Known Member

    I’ve never used live-view so can’t answer.
     
  5. PeteRob

    PeteRob Well-Known Member

    :) We went to Attingham Park on the off-chance the snowdrops were out. They are, but probably better in a couple of weeks. There is a themed “love the planet/environment” installation, based on yarn-bombing the mile walk with green hearts. These few were particularly bright
     
  6. RogerMac

    RogerMac Well-Known Member

    It is quite possible that light from luminous objects is polarised and this might affect the AF. If you have polarised filters this would be easy to check.
     
    daft_biker likes this.
  7. Bazarchie

    Bazarchie Well-Known Member

    I will wait a few weeks before attempting snowdrops. Not an easy subject, at least not for me, but satisfying when you get it right. It has become a bit commercialised in the last few years with several places near us charging highest entry fees. Last year I found a churchyard covered with snowdrops and winter aconites but the results were not my best. Seems to be easier when they are not just at ground level.
     
  8. Learning

    Learning Ethelred the Ill-Named

    Snow drops are not difficult provided you reduce exposure so they don't burn out.
    I hope that I have been genuinely constructive. My initial thought was just to write "Should have gone to Nikon" but that would just have been a silly joke at the expense of a certain company that sells specs. A bit later in the year we will have wood anemones. Same problem only more so because of more advanced foliage on the trees. Both subjects are easily dealt with. Shoot raw with a camera with good dynamic range, develop in a 32 bit workspace so you can increase the shadows (exposure adjustment) without burning out the snowdrops, and then map your tones to fit 16 bit processing package format, and eventual 8 bit jpeg.
    A far more tricky subject will soon flower. Blue bells. Now getting bluebells right is a different matter. Even more difficult if you want them to look good on all of a more or less sRGB un-calibrated screen, an Adobe calibrated screen, and any printer of any sort. I don't think that it can be done. If anyone does know how then please tell us. Bluebells must be the ultimate test of end to end colour reproduction.
     
  9. Bazarchie

    Bazarchie Well-Known Member

    Interesting, I find bluebells easier than snowdrops and I have no problems with wood anemones.
     

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