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Thread: 90 inch bellows - what is exposure?

  1. #31

    Join Date
    Apr 2015
    Location
    Vermont, USA
    Posts
    2

    Re: 90 inch bellows - what is exposure?

    Um.. what about the "no shutter" part of the description? A fractional shutter speed is going to be a challenge using the lens cap..

    - JasOn

  2. #32

    Re: 90 inch bellows - what is exposure?

    In retrospect the photographer has three critical areas in this objective that need certainty because in 20x24 format mistakes are very costly. First he needs to verify the correct base exposure which seems anomalous to me as stated. Spot meter caucasian skin and place on zone 6. The second driver in this instance is he has a barrel lens and needs longer exposure times he can manage properly. I would shoot for about one second because that is the baseline for this application. Maybe someone has skill to pull off a half second with a barrel lens -then I tip my hat to them figuratively speaking. Lastly as I previously stated reading an easily seen square wafer at the plane of focus with a proper scale on the ground glass is uniquely simplistic and takes all of the "though" gymnastics out of the process. The scale immediately tells the photographer the bellows correction that is optically in play - any lens, any camera, and any magnification. Been using this for years on 8x10, 11x14 and 8x20 and it has never let me down. If there is one thing I have learned with ULF and that massive expanse of ground glass that needs considerable time to ensure it is all dialed in is "keep it simple" because while the images it produces are the reason we go down this road, the chances for little errors that can muck up an image increase proportionally with format size.

    Hoping the photographer was able to get his shot.

  3. #33

    Join Date
    Aug 2019
    Posts
    23

    Re: 90 inch bellows - what is exposure?

    Hi Rich,

    I recently bought a Korona view 11x14" / refurbished

    As I am very new to all of this. And i Have no films yet. Only reading and learning

    I also still wonder how to calculate the right shutter speed accordingly the how much I extend my lens away from the "film level"

    In your formula you wrote:

    the length of the bellow ...measured from where to where? Lens ground plate to the Film? I measure in cm

    Divided by the lens focal length. I use a Schneider Kreuznach Symmar S 360mm f6.8 . ... so i stick to 360mm in the calculation? or will these mm change soon as move the bellow?

    ALSO: if my lens starts with f6.8 my first stop would start with f6.8 then instead of 2, 4, 8, ... up to f90 ? do i get this right?
    1 stop = 2x.
    2 stops = 4x.
    3 stops = 8x.
    4 stops = 16x.

    how do I involve the ISO with the whole calculation... also for later on with wet plates?

    Filmes I will get for the first go's will have ISO50

    thanks for helping

    farid

  4. #34

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,744

    Re: 90 inch bellows - what is exposure?

    2x magnification requires 4 stop additional exposure. So 1/60th.

  5. #35

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    7,570

    Re: 90 inch bellows - what is exposure?

    Farid, I've already suggested that you buy and study a copy of Lester Lefkowitz' book The Manual of Close-up Photography. It has the answers to your questions about extension, and more.

    Your later question suggests that you're not acquainted with the idea "light meter." You need one. You need to know how to use it.

    In other words, learn the basics so that you'll be able to think for yourself. I think I gave you a link to the list. It has a section on books on LF photography that are often recommended to beginners. Buy one of them and study it.

  6. #36

    Join Date
    Aug 2019
    Posts
    23

    Re: 90 inch bellows - what is exposure?

    hi Dan, let me check again thanks... i found that list.. but where to start

    thanks
    farid

  7. #37

    Join Date
    Aug 2019
    Posts
    23

    Re: 90 inch bellows - what is exposure?

    Quote Originally Posted by Dan Fromm View Post
    It has a section on books on LF photography that are often recommended to beginners. Buy one of them and study it.
    which one would you get if you were me? I live in switzerland so it will be a foreign book store order...

    cheers
    farid

  8. #38

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,744

    Re: 90 inch bellows - what is exposure?

    Rather then worrying about focal length, bellows extension it is much easier to learn about magnification.

    ½ lifesize - open 1 stop.
    1:1 lifesize - open 2 stops.
    2:1 twice lifesize open 4 stops.

    To make it easy put a ruler in the scene by the subject and measure an increment on the gg.

  9. #39

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    7,570

    Re: 90 inch bellows - what is exposure?

    Quote Originally Posted by Farid View Post
    which one would you get if you were me? I live in switzerland so it will be a foreign book store order...

    cheers
    farid
    The ones recommended are all good. I have Stroebel. Look for sellers on abebooks.com, alibris.com, amazon.com, bn.com, ... Also try Amazon sites in the EU, e.g., amazon.de.

  10. #40

    Join Date
    Aug 2019
    Posts
    23

    Re: 90 inch bellows - what is exposure?

    Hi Dan
    just ordered one from .. Lebowitz or similar.. i also got a german one from a swiss guy called Peter Michel "Kollodium" . very precise lots of different kollodium recipies temperature calculations etc.. will start reading today. https://www.fotokultur.ch/shop/das-kollodium/ her also does courses and workshops. Will attend to join in october if i manage.

    thanks

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