Results 1 to 3 of 3

Thread: determining point focused on from bellows extension

  1. #1

    determining point focused on from bellows extension

    I can I tell what point I am focused on from my bellows extension. The only len s I have is a 150MM. It appears that I need to know this to use any of the dept h of field tables

  2. #2

    Join Date
    Mar 1999
    Posts
    69

    determining point focused on from bellows extension

    Are you trying to determine focus distance using bellows extension as a yardstick? That can be tough; it's usually easier to measure with a tape measure (at closer distances) or guesstimate (at greater distances) the distance to the portion of the subject that's in focus.

    Perhaps you could rephrase the question? The "I can I tell" phrase is particularly mysterious. . . .

  3. #3

    determining point focused on from bellows extension

    I have answerd my own question. The formula I was looking for is: 1/focal length = (1/object distance) + (1/image distance)

    object distance is the lens plane to real world object length

    image distance is the lens plane to film plane distance (in other words the bellows extension

    Thus with a 150mm lens and the bellows extended approximatly 6.3" you are focused at 10'

Similar Threads

  1. Bellows Extension calculation
    By Jonathan Brewer in forum Style & Technique
    Replies: 15
    Last Post: 20-Jun-2010, 14:21
  2. Bellows Extension Design
    By Bruce E. Rathbun in forum Cameras & Camera Accessories
    Replies: 10
    Last Post: 9-Aug-2005, 19:04
  3. Setting minimum bellows extension
    By Carl Schofield in forum Style & Technique
    Replies: 4
    Last Post: 17-Nov-2003, 17:39
  4. Bellows extension, portrait capability.
    By Bill Ballhorn in forum Lenses & Lens Accessories
    Replies: 4
    Last Post: 9-Apr-2001, 20:49
  5. Compensating exposure for bellows extension
    By Robert Ruderman in forum Style & Technique
    Replies: 9
    Last Post: 21-Aug-1999, 21:55

Bookmarks

Posting Permissions

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