Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,760   Posts: 1,516,081   Online: 889
      
Page 7 of 9 FirstFirst 123456789 LastLast
Results 61 to 70 of 81
  1. #61

    Join Date
    Jul 2007
    Location
    Netherlands
    Shooter
    Medium Format
    Posts
    5,686
    Quote Originally Posted by John Koehrer View Post
    IMO Greg's got the easiest solution and is more or less what I use.
    My method(?) goes like this:
    With a 150mm/6" lens,
    infinity=0,
    275mm/9"=1 stop,
    300mm/12"=2 stops.
    Halfway between gets half the correction 1/3 gets 1/3 the correction. Plus or minus depending which side you're measuring from.
    With my hand, 9" is the spread from thumb to little finger whilst hanging ten.
    Your "275mm/9"=1 stop" is off target by as much as 0.75 stops (should be 1.75 stops).
    1 stop would be at 212 (and a bit) mm.

  2. #62

    Join Date
    Nov 2009
    Shooter
    35mm
    Posts
    173
    Quote Originally Posted by Terry Bowyer View Post
    http://www.youtube.com/watch?v=vwfRA615Mx8

    I just came across this video on youtube that kind of explains bellows extension compensation. Thanks jason Brunner. Hope this helps someone else.
    I just had to see it again. Jason is really good at doing those videos, they are both fun and educative.

  3. #63

    Join Date
    Aug 2006
    Location
    Hamilton, Ont, Canada
    Shooter
    Large Format
    Posts
    991
    perhaps he meant 225mm
    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

    Regards
    Bill

  4. #64
    hcm
    hcm is offline

    Join Date
    Apr 2010
    Shooter
    4x5 Format
    Posts
    3
    As the lens gets further from the film the light passing though the lens is spread over a wider area and proportionately less falls on any given area. The proportion is based on the square of the change in distance. Thus if the lens were twice as far away the light would be diffused over an area twice as high and twice as wide so the adjustment would be based on one quarter of the light hitting any area of film and the adjustment would be 2 f stops.

  5. #65
    stradibarrius's Avatar
    Join Date
    Jan 2009
    Location
    Monroe, GA
    Shooter
    Medium Format
    Posts
    1,382
    Images
    163
    I .tried measuring my bellows extension for this shot the bellows from the film plane to the lensboard is 16". My lens is 180mm. If I square the extension and divid by the square of my lens length I come up with 5 stop bellows factor??? Is this right?
    Obviously this is a very close up shot. This is the total extension of the bellows.
    "Generalizations are made because they are generally true"
    Flicker http://www.flickr.com/photos/stradibarrius
    website: http://www.dudleyviolins.com
    Barry
    Monroe, GA

  6. #66
    rmolson's Avatar
    Join Date
    Feb 2006
    Location
    Mansfield Ohio
    Shooter
    Medium Format
    Posts
    307
    The Kodak Master Photoguide has a very comprehensive f number computer and simple way of determining exposure correction I have one taped to the back of my view camera glass cover.That and a pocket tape measure and you can figure the correction in seconds with out all the math. If I have a 6 inch lens 8 inches from the film plane my exposure should be increased by one stop.

  7. #67
    Bruce Osgood's Avatar
    Join Date
    Sep 2002
    Location
    Brooklyn, N.Y. USA
    Shooter
    Multi Format
    Posts
    2,415
    Images
    43
    Strad,

    I did the math and keep a copy in my bag


    FILTER FACTOR & STOPS

    FACTOR.. ..STOPS
    1 0.0
    1.5 0.6
    2 1.0
    2.5 1.3
    3 1.6
    3.5 1.8
    4 2.0
    4.5 2.2
    5 2.3
    5.5 2.5
    6 2.6
    6.5 2.7
    7 2.8
    7.5 2.9
    8 3.0
    8.5 3.1
    9 3.2

  8. #68
    Bruce Osgood's Avatar
    Join Date
    Sep 2002
    Location
    Brooklyn, N.Y. USA
    Shooter
    Multi Format
    Posts
    2,415
    Images
    43
    OOP'S

    the format did not hold up.

    The FACTOR should read as a number and decimal point, IE: factor of 1 is 1.0, 1-1/2 is 1.5.
    The STOP numbers are one decimal point also, IE: STOP of 1 is 0, STOP of 1.5 is 0.6

    Sorry the column spacing between the numbers didn't work.

  9. #69
    Bruce Osgood's Avatar
    Join Date
    Sep 2002
    Location
    Brooklyn, N.Y. USA
    Shooter
    Multi Format
    Posts
    2,415
    Images
    43
    John, I agree.

    I made the all to common mistake of answering the wrong question.

    I was addressing filter factors and not bellows extension.

  10. #70
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    the villages .centralflorida,USA and Germany
    Shooter
    Multi Format
    Posts
    6,344
    Images
    1
    Quote Originally Posted by Terry Bowyer View Post
    Is anyone out there able to give me an easy to understand explanation of this 'bellows extension compensation' that I have been hearing about. Just bought my first 4x5 camera (Zone VI) with a 210mm and 80mm lens. I haven't taken any photos yet, but like to be prepared for when I do.
    try thisand start on pge 192!
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin