A&P apeture and image sharpness

Discussion in 'Lifestyle' started by sex_xer, Mar 30, 2005.

  1. sex_xer

    sex_xer fuck you 2by2!

    Joined:
    Apr 3, 2002
    Messages:
    268
    Likes Received:
    0
    Location:
    #houston
    is there a formula that can be used to figure out what objects will be sharp in certain aperture by distance?

    what do you guys do? take several shots in an several aperture size and increase or decrease the size accordingly to get the desired effect? is there a general consensus?
     
  2. Nick

    Nick Guest

    I'm assuming you are talking about depth of field? If so, an SLR usually has a dof preview button so you can see what will be in focus. On a POS, the lens is typically so small that you'll pretty much have a huge dof all the time and anything near your focus point will be in focus.
     
  3. sex_xer

    sex_xer fuck you 2by2!

    Joined:
    Apr 3, 2002
    Messages:
    268
    Likes Received:
    0
    Location:
    #houston
    yeah its dof. i have a 20D and i used the dof preview button, on the left side of the lens barrel if i remember correctly. from the view finder it blurs a little but i dont see how it predicts dof. what am i suppose to be looking for?
     
  4. vizual

    vizual → 190½ ЯBI ←

    Joined:
    Oct 23, 2001
    Messages:
    13,086
    Likes Received:
    0
    Location:
    Gouge Eye, Ca
    The blurring would be caused to a decreased depth of field. If you have a lens like a 50mm f/1.8 and you open it to 1.8 you can have a smaller area of the picture infocus, whether it be something in the foreground/background/etc and the rest fall out of focus. If you look in this thread http://forums.offtopic.com/showthread.php?t=1694309 you'll see examples of depth of field and how it blurs and makes the infocus part of the picture really seperated from the background.
     
  5. Nick

    Nick Guest

    Let's say you are trying to take the picture in the thread vizual linked, with the boy on the right and the Buzz Lightyear toy on the left. You want the boy and the toy in focus and the background out of focus. Focus on the boy, compose your shot and hold the dof preview button. If the toy is out of focus, close down the aperture some and hit the dof preview again until it is in focus. If you have the opposite problem and the background is in focus, open the aperture some and hit the dof preview again until the background is out of focus. There aren't really any formulas or rules that I know of, but as you take more pictures you'll get a feel for it. Just make sure you are focused on your main subject before hitting dof preview or it won't help at all.
     
  6. Nick

    Nick Guest

    :eek3:
    Someone must have spent ages making that. Seems almost useless for practical applications though. :dunno:
     
  7. chlywly

    chlywly Active Member

    Joined:
    Dec 15, 2000
    Messages:
    18,745
    Likes Received:
    1
    Location:
    Toronto
    Well most SLR lenses are sharpest at about f8-10
     
  8. sex_xer

    sex_xer fuck you 2by2!

    Joined:
    Apr 3, 2002
    Messages:
    268
    Likes Received:
    0
    Location:
    #houston
    thanks for the inputs guys
     
  9. mojito

    mojito New Member

    Joined:
    Mar 8, 2003
    Messages:
    62,877
    Likes Received:
    0
    Almost always the lens will be sharpest at 2 stops from wide open, so say F/4 on a F/2 lens. DOF will increase but overall sharpness will not. After F/16-22, you will start to lose sharpness from the aperature blades causing distortion
     
  10. in for later
     
  11. Fucker

    Fucker out of the fast lane, bitches

    Joined:
    Jan 28, 2005
    Messages:
    11,538
    Likes Received:
    0
    Location:
    The Left Coast
    Truth, but sharpness isn't dof.
     

Share This Page