Tele-Converter Question

Discussion in 'Photography Equipment & Products' started by firemedic0135, Jan 20, 2007.

  1. firemedic0135

    firemedic0135 TPF Noob!

    Joined:
    Jan 16, 2007
    Messages:
    503
    Likes Received:
    1
    Location:
    East Texas
    Can others edit my Photos:
    Photos OK to edit
    Hey guys another newbie question for you.I was looking at these teleconverters and had a question about the reaction to aperture size while using on.They said it decreases av by 2 stops..What would that be with a 1.7,or 4.0?
    any help is appreciated as always.:thumbup:
     
  2. tpe

    tpe TPF Noob!

    Joined:
    Nov 18, 2005
    Messages:
    964
    Likes Received:
    12
    Location:
    Copenhagen Denmark
    Can others edit my Photos:
    Photos OK to edit
    If that is from 1.7 then 1 stop would be 2.4 then the second would take it to 4.8? I think starting at 1.7 is a little odd as normally you would start from 1.4 hence the odd f stops.

    tim
     
  3. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

    Joined:
    Aug 25, 2003
    Messages:
    7,021
    Likes Received:
    34
    Location:
    Lawrence, KS
    Can others edit my Photos:
    Photos NOT OK to edit
    Doubling the f/# = 2 stops, so 2 stops less than f/1.7 would be f/3.4.

    Teleconverters effectively increase focal length. f/# = focal length divided by the actual size of the aperture. A x1.4 teleconverter reduces aperture 1 stop, and a x2 teleconverter 2 stops, no matter what aperture setting you are using.

    SLR lenses stay at their max aperture for focusing and framing, and then it closes down to the set aperture right before exposure. Many AF systems begin to fail when the max aperture gets to f/8 or smaller (higher number). This is why teleconverters affect the AF with zooms with a max aperture of f/5.6. It turns them into f/8 or f/11 zooms.
     

Share This Page