Question Regarding DOF abd Long Glass

Discussion in 'General Discussion' started by jfenton, Sep 11, 2005.

  1. jfenton

    jfenton

    Jan 26, 2005
    Haverhill, MA
    Ladies and Gentlemen:

    I have always been perplexed when I see others shooting long glass at f4 and 5.6 on moving birds...big birds...and the entire bird is within the DOF from wingtip to wingtip.

    Most of the linked shots (from Fred Miranda) were shot with a 400 MM lens on a Canon body...not that the manufacturer makes a difference.

    How come when I'm shooting a 500 at f7.1 or 8 even (with no TC), there is no way in hell I could have the entire animal withing the DOF?

    Someone please explain this to me?????

    http://www.fredmiranda.com/forum/topic/278869
     
  2. Bob Coutant

    Bob Coutant Moderator Moderator

    May 17, 2005
    Pleasantville Ohio
    Jim -- How far away are you? At 40-50 yards, you should have enough DOF for a pretty big bird.

    DOF is a function of focus distance, amongst other things. At http://www.dofmaster.com, you can get a free program for generating charts of DOF that are specific for your camera/lens combination. [They also have an extensive tabulation of circle-of-confusion (coc) values for most cameras, including the D2X.]
     
    Last edited by a moderator: Sep 12, 2005
  3. Thanks for posting this question. I see this type of shot, especially of raptors in the British 'Bird Watching Magazine,' and wonder how the hell they can get such results.

    Best wishes

    Bob F
     
  4. MontyDog

    MontyDog

    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
     
  5. Wild guess...

    Could it be they manage to shoot at the lens' hyperfocal distance?
     
  6. Flew

    Flew

    994
    Jan 25, 2005
    Alabama
    Hey, I'm not Ron R (obviously), but depending on what figure one uses for the circle of confusion, at 500mm / f8, the DOF is between 36 and 46 inches (COC = 0.016 or 0.020). At 150 feet the values are 84 and 104 inches.

    I have a spreadsheet that gives a pretty good look at this at various apertures and cam-to-subject distances that I can send you if you like.
     
  7. Flew

    Flew

    994
    Jan 25, 2005
    Alabama
    The Hyperfocal distance for a 500mm lens at f8 is over 5,000 feet, so I doubt that this is how they are getting good DOF. :smile:
     
  8. I'm with Beezle here, hyper-focal distance would give you the greatest DOF for the bird itself. Selective sharpening is another way to gain apparent overall sharpness.
     
  9. Doh! Well, I would image that a bird at that distance would be a single pixel at best and probably very sharp! :rolleyes:

    Wild guess No. 2:

    Perhaps they are doing a lot of cropping? Seems to me a subject filling half the frame would be in a much larger DOF than a subject filling the frame. If that makes sense.
     
    Last edited by a moderator: Sep 12, 2005
  10. Flew

    Flew

    994
    Jan 25, 2005
    Alabama
    True. :biggrin:
     
  11. MontyDog

    MontyDog

    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
     
  12. MontyDog

    MontyDog

    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
     
  13. I would love a copy. I'll PM an email address.
     
  14. Flew

    Flew

    994
    Jan 25, 2005
    Alabama
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