A&P does a larger maximum aperture offer any advantages other than smaller dof/more light

Discussion in 'Lifestyle' started by White Stormy, Feb 3, 2009.

  1. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    like, if I'm using a 50/1.4, but taking a photo at f/1.8, does the lens use the 1.4 aperture for a more accurate/faster autofocus or anything before dropping to f/1.8 for the pic?

    if not.. then doesn't the difference between like a 70-200/2.8 and 70-200/4 really only become noticeable (ignoring for now that they might have a diff number of elements, etc) at an aperture on the 2.8L larger than f/4? depth of field at that focal length can get crazy small even on a f/4.. many people may not ever need the 2.8
     
  2. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    my point is that if it doesn't use the max aperture for something else.. the retardedly shallow dof at a long focal length may mean that you don't ever use the higher aperture at all

    30D + 200/4 + 30ft subject = 1.02ft dof
    30D + 200/2.8 + 30ft subject = .72ft dof
     
  3. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    I just realized a flaw in my logic.. dof grows more than I expected at longer subject distances.. but my question was really just if the max aperture is used by the lens for stuff even when using an aperture other than the max.
     
  4. Mutombo

    Mutombo New Member

    Joined:
    May 31, 2006
    Messages:
    5,289
    Likes Received:
    0
    Location:
    San Francisco
    The camera will focus using the maximum aperture of the lens. Some AF sensors are more sensitive at larger apertures, so the AF can be more accurate with a f2.8 lens than with a f4 lens on certain bodies.
     
  5. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    :-D thanks

    that's what I thought/hoped, but wasn't really sure
     
  6. alexromo

    alexromo New Member

    Joined:
    Jul 10, 2005
    Messages:
    4,571
    Likes Received:
    0
    Location:
    Wahiawa
    i would say the ability to use a faster shutter speed
     
  7. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    ..you mean slower?
     
  8. alexromo

    alexromo New Member

    Joined:
    Jul 10, 2005
    Messages:
    4,571
    Likes Received:
    0
    Location:
    Wahiawa
    instead of shooting 1/250, i shoot 1/500 or sometimes 1/1000
    with a larger maximum aperture
    :)
     
  9. White Stormy

    White Stormy Take that, subspace!

    Joined:
    Sep 17, 2002
    Messages:
    85,486
    Likes Received:
    69
    Location:
    Sparkopolis
    I've been dealing with banks and credit card companies all day. apparently my head's on backwards. :uh:
     
  10. xenon supra

    xenon supra OT Supporter

    Joined:
    Feb 3, 2005
    Messages:
    33,675
    Likes Received:
    0
    Location:
    San Diego, CA
    faster glass usually means higher quality which usually means better IQ.
     
  11. Spurious

    Spurious New Member

    Joined:
    Jan 15, 2006
    Messages:
    27,219
    Likes Received:
    0
    Location:
    Houston, Texas Bans: 5
    This.

    Lenses are usually somewhat soft at their maximum aperture and gain sharpness the higher you go. A lens that is F/1.8 will be sharper at 4.0 than an F/4.0 lens at 4.0.
     
  12. mobbarley

    mobbarley Active Member

    Joined:
    Mar 4, 2005
    Messages:
    9,256
    Likes Received:
    2
    Location:
    Sydney
    and they contain more glass so they are heavier - making them better weapons.
     
  13. xenon supra

    xenon supra OT Supporter

    Joined:
    Feb 3, 2005
    Messages:
    33,675
    Likes Received:
    0
    Location:
    San Diego, CA
    the beast ftw.
     
  14. Mutombo

    Mutombo New Member

    Joined:
    May 31, 2006
    Messages:
    5,289
    Likes Received:
    0
    Location:
    San Francisco
    the brick > the beast
     
  15. xenon supra

    xenon supra OT Supporter

    Joined:
    Feb 3, 2005
    Messages:
    33,675
    Likes Received:
    0
    Location:
    San Diego, CA
    :squint:
     
  16. Sympathy

    Sympathy OT Supporter

    Joined:
    Mar 18, 2006
    Messages:
    31,010
    Likes Received:
    79
    you also get softer bokeh with a wider aperture
    [​IMG]
     

Share This Page