Home News Buyers Guide About Advertising
 
 
 
   
Page 1 of 19 12311 ... LastLast
Results 1 to 10 of 183

Thread: Apature

  1. #1
    Join Date
    Jun 2007
    Posts
    79

    Apature

    So heres another nubbish question from me :P ... So i was wondering if lets say i have a 70-200mm f/2.8 lens what exactally does the appature on the camera do? isnt it fixed at f/2.8? thanks

  2. #2
    Join Date
    Aug 2007
    Location
    Brisbane, CA
    Posts
    3,591
    You're right, that is newbish! f/2.8 is the max aperture which is available throughout the focal range. If you see something like f/3.5-5.6 then that means the max aperture is 3.5 at the wide angle end with a max of 5.6 at the telephoto end of the focal range.
    Lukas

    Camera: Anonymous
    I could tell you but I wouldn't want you to get all pissy if it's the wrong brand

    Flickr

  3. #3
    Join Date
    Mar 2007
    Posts
    1,923
    No, it isn't fixed at f/2.8, it's just the maximum aperture remains f/2.8. You can still "stop down" to smaller apertures (larger f/numbers).

    Edit: Wengler beat me to it. And I was quick, I thought!
    Last edited by fionndruinne; 10-22-2007 at 10:55 PM.
    Nikon D40 + kit lens

    Nikkor 50mm f/1.8 D AF(...or not)

  4. #4
    Join Date
    Dec 2006
    Location
    So Calif
    Posts
    3,226
    First off, the word is "aperture".

    The aperture is the hole formed by the blades of the diaphragm of the lens. The actual size of the aperture is calculated by dividing the focal length by the f-number. The smaller the f-number, the larger the aperture and the more light it can let in at any given shutter speed. Depending on the lens, the maximum aperture can stay constant, or change to a larger f-number as the focal length increases. Large aperture/constant aperture lenses are the more expensiv versions.
    Pentax K20D/K5/15/21/40/70/10-17/12-24, Sigma 17-70 2.8-4.5/150-500, Tamron 90 Macro/70-200 2.8, Canon SX20 IS/Elph 500HS
    (formerly Pentax 50 1.4/50-200/55-300/K100D, Sigma 18-50 2.8/70-300 APO, Tamron 28-75, Viv 800, Tele-Tokina 800, Canon S3 IS, Samsung L210)
    http://s133.photobucket.com/albums/q78/KylePix/

  5. #5
    Join Date
    Jun 2007
    Posts
    79
    So... You mean like for the 17-70 sigma... its F/2.8-4.5 which means at 17ish its maxed at 2.8 and 70 its maxed at 4.5? so it cant go below 4.5 at 70 but like the 70-200 F/4 COULD go to f/4 at 70 AND 200? so its just the max? and its not fixed and can be shrunk? thanks BTW those were fast replies!

  6. #6
    Join Date
    Aug 2007
    Location
    Brisbane, CA
    Posts
    3,591
    Quote Originally Posted by Zeva View Post
    So... You mean like for the 17-70 sigma... its F/2.8-4.5 which means at 17ish its maxed at 2.8 and 70 its maxed at 4.5? so it cant go below 4.5 at 70 but like the 70-200 F/4 COULD go to f/4 at 70 AND 200? so its just the max? and its not fixed and can be shrunk? thanks BTW those were fast replies!
    Yep, you got it.
    Lukas

    Camera: Anonymous
    I could tell you but I wouldn't want you to get all pissy if it's the wrong brand

    Flickr

  7. #7
    Join Date
    Jun 2007
    Posts
    79
    haha ty for help w/ nubbish question

  8. #8
    Join Date
    Oct 2006
    Posts
    461
    Quote Originally Posted by Zeva View Post
    So... You mean like for the 17-70 sigma... its F/2.8-4.5 which means at 17ish its maxed at 2.8 and 70 its maxed at 4.5?
    Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
    The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.

  9. #9
    Join Date
    Mar 2007
    Posts
    1,923
    Uh... only at f/4.5, Razr. Not at f/2.8.
    Nikon D40 + kit lens

    Nikkor 50mm f/1.8 D AF(...or not)

  10. #10
    Join Date
    Oct 2006
    Location
    Taipei, Taiwan/from Canada
    Posts
    1,313
    Quote Originally Posted by Razr View Post
    Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
    The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.
    Maybe I misread your post here but I think you are wrong. If you are in Av or M mode with a f/2.8-f4.5 lens on your camera and your Aperture is set at f/2.8, as you zoom the aperture will not stay at f/2.8, it cannot. It will change to match the max aperture to that specific focal length. So the sigma 17-70 f/2.8-4.5 has a max aperture of f/2.8 only at 17mm and a max aperture of f/4.5 at 70mm.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •