Focal length affect focusing distance

Discussion in 'Photography Beginners' Forum' started by jamesino, Apr 20, 2008.

  1. jamesino

    jamesino TPF Noob!

    Joined:
    Dec 9, 2007
    Messages:
    115
    Likes Received:
    0
    Can others edit my Photos:
    Photos OK to edit
    Does zooming in with a lens affect its minimum focusing distance? For example, suppose if I have a 100-200mm lens with a minimum focus distance of 1m. Does that mean regardless of which focal length i'm zoomed in to, the minimum focusing distance will always be 1m? Therefore, the "macro-est" shots should be taken at the 200mm end at 1m away?
     
  2. JimmyO

    JimmyO TPF Noob!

    Joined:
    Feb 3, 2008
    Messages:
    2,132
    Likes Received:
    0
    Location:
    NJ
    Can others edit my Photos:
    Photos NOT OK to edit
    it does not affect it im pretty sure. Shouldnt be hard to just experiment.
     
  3. christopher walrath

    christopher walrath No longer a newbie, moving up!

    Joined:
    Mar 19, 2008
    Messages:
    1,265
    Likes Received:
    23
    Location:
    In a darkroom far, far away...
    Can others edit my Photos:
    Photos NOT OK to edit
    This is an excerpt from a piece I am working on.

    Focusing a lens is rather simple. There is a focusing ring around the outside of the lens. When this ring is turned to the right it focuses the lens closer to the camera. When it is turned to the left then the focus is extended away from the camera. No matter how far away from the camera the lens is focused there will always be a certain area of the space before and after that point that will be in acceptable focus. This is referred to as depth of focus. An area of space in front of the lens that will appear to be reasonably sharp exists from in front of the point of focus to past it. The area in front of the point of focus is usually around one half the amount of space behind the point of focus that is in reasonably sharp focus. This actual spatial distance is called the hyperfocal distance and changes depth as the aperture is changed. A larger aperture causes a shorter depth of focus because it gathers from a larger spatial area this shortening depth of focus. A smaller aperture has a much greater depth of focus due to drawing light from a much smaller spatial area.

    In answer to your direct question, the lens is fabricated with the ability to focus down to a certain imnimum distance and, though the depth of focus is affected, the minimum focusing distance is not.
     
  4. Helen B

    Helen B TPF Noob!

    Joined:
    Sep 16, 2007
    Messages:
    3,296
    Likes Received:
    465
    Location:
    Hell's Kitchen, New York
    Can others edit my Photos:
    Photos NOT OK to edit
    Whether or not the minimum focus distance varies with focal length depends on the lens. There are some zooms that are able to focus much closer when zoomed out than when zoomed in.

    Chris,

    Not all lenses focus the same way. For example Leica and Nikon work in opposite directions.

    You are referring to depth of field, not depth of focus. Depth of focus is the equivalent of depth of field but in the image plane rather than the object plane.

    The depth of field in front of the focused plane (the near depth of field) is not always half of the depth of field behind the focused plane (the far depth of field).

    When a lens is focused on the hyperfocal distance for the working aperture, the far depth of field extends to infinity. That's what hyperfocal distance means.

    Best,
    Helen
     
  5. dEARlEADER

    dEARlEADER TPF Noob!

    Joined:
    Apr 9, 2008
    Messages:
    1,312
    Likes Received:
    1
    Location:
    Canada
    Can others edit my Photos:
    Photos OK to edit
    snap
     
  6. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    I have a 28-70mm Tokina lens from way back when which would not allow you to get anywhere near the closest focusing distance unless it was zoomed all the way out. It was a strange beast in that it's 1:3.5 "macro" was achieved at the wide end not when zoomed in.
     

Share This Page

Search tags for this page
does distance effect focus
,
does focal length affect focus?
,

focus and focal length

,
focus distance varies from focal length
,
how camera focal length affects zoom and focus
,
how does distance affect focal length
,
how does focal lenght affect focus
,
how does focal length affect focus
,

how does focal length affect minium distance

,
how focal length affects minimum focus distance