Shooting Provia 100 without bellows extension

Discussion in 'Color: Film, Paper, and Chemistry' started by colrehogan, Mar 27, 2006.

  1. colrehogan

    colrehogan Member

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    I asked this on the LF forum too, but though I'd ask here to see if anyone had any ideas.

    This weekend, a friend of mine wanted to test his new lighting equipment. I took my 8x10 to his house to shoot some pics, but left my expo disc at home (duh!) I am fairly sure I needed some sort of bellows compensation. I was shooting Provia 100 (metered and exposed for ISO 100), with a 19 in. APO Artar lens.

    My question is, should I have the lab push these sheets by a stop since I didn't compensate for bellows extension before hand (or can I do anything about it in the developing stage)?

    I took some snow shots last week on a couple of sheets of Provia (metered and exposed for ISO 100). Would pushing a stop help these images?
     
  2. mark

    mark Member

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    How did you meter the snow? I assume you are saying that you made no exposure compensation at all, right? Either way it depends on how you metered. But, in general, I have found that to get a good snow exposure on Provia you have to open up 1.5 stops. A one stop push will get you close but the snow will still be pretty grey.

    Do you have any idea how far your bellows was racked out past infinity on the lighting shoot? A simple guess will help.

    Provia, my film of choice, washes out real quick with too much exposure. Pushing the film past what your compensation should have been will make for an ugly tansparency. If you want to be safe, maybe they can only push it half a stop.
     
  3. colrehogan

    colrehogan Member

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    On the snow shots, I think I did open up thinking that it would need it as it not only because of the snow but also, it was an overcast day. I'll have to check my notes at home.

    It was the studio shots that I didn't compensate for. As for how far the bellows was racked out for the studio shots, I haven't a clue.
     
  4. BradS

    BradS Subscriber

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    Hi Dianne,

    With respect to the bellows factor, you say you were shooting a 19inch lens. How far away was your subject? Given this info, we can calculate the image distance - that is, the distance from the lens to the film - the length of the bellows if you will.

    Once we know the image distance, the bellows factor is given by:

    factor = ( image distance / focal length ) ^2


    Let's suppose for example that you were focussed on a subject about 36 inches away. With a 19 inch lens, you'd need about 40 inches of bellows (very rough). With 40 inches of bellows and a 19 inch lens, the bellows adjustment would be:

    bellows factor = (40 / 19) ^2 = (40/19)*(40/19) = 4.5

    or, a little more than two stops.

    Brad.
     
  5. colrehogan

    colrehogan Member

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    Well, my camera only has 29 inches of bellows and it was not overly stretched for the studio shot (nor for any other shot I've taken with it). I would guess that the subject in the studio was probably about 6-8 ft away from the lens plane.
     
  6. BradS

    BradS Subscriber

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    OK, Let's assume the worst case. You were focussed at 6 feet. With a 19 inch lens, that would require 25.8 inches of lens-to-film distance. The bellows factor in that case would be:

    factor = (25.8 / 19) ^2 = 1.84 or, about one stop (actually, 0.88 stops but...close enough)

    so, asking your lab to push process these between two thirds to one stop seems entirely reasonable.
     
  7. colrehogan

    colrehogan Member

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    Thanks to all who have replied. I'll try and have my act together next time and remember to do the bellows compensation.