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Thread: Studio exposure/development test for black and white film illuminated with strobes

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    Peter De Smidt's Avatar
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    Studio exposure/development test for black and white film illuminated with strobes

    I've been concentrating lately on studio work with strobes. At first, I tried the old "just do it" method, but I wanted to get a little more systematic. I'm not an expert, but I've been exposing and developing film for a long time, and so hopefully I'm not too off base. If I am, please correct me!

    We all know that exposure predominately effects the darker areas of the scene, whereas development mainly effects the brighter areas. In landscape photography, you can use a spot meter to place detailed shadows on Zone III, which should lead to bright areas falling on Zone VIII for a normal scene, and you use the exposure and development that'll give you the appropriate film densities for your intended use. If you have a non-normal scene, you adjust exposure and development to compensate. (You don't _have_ to have the bright areas fall on Zone VIII. You can adjust exposure and development to give the overall look that you're after. I regularly let the bright areas fall higher than Zone VIII. Many current films have a very straight line response to more exposure.)

    If I had a spot meter that worked with flash, I'd be all set, as I could do the same thing I do for a landscape with a subject in the studio. But I don't have one. I only have incident flash meters.

    So the procedure for landscapes with incident meters is to meter sun and shade to find the subject illumination range. You then set the meter to twice the film speed and take a shade reading. That's the exposure, and then you develop according what's indicated by your subject illumination range. (This incident stuff is all Phil Davis Beyond the Zone System.)(See Ken Lee's excellent "The Myth of the 18% Gray Card" at: http://www.kenleegallery.com/html/tech/index.php)

    So in the studio, fill light = shade, and fill light + main light = sun, as the brightest parts of the image will receive light from both the fill light and the main light, whereas the shadowed areas will only receive light from the fill.

    I did the following test. I set up two MacBeth Colorcheckers on a black flag. Between them, and perpendicular to to the first flag, I added another flag. I placed the main light on the right such that it'd only illuminate the right color checker. I placed the fill light right above the camera, such that it would light both color checkers. I entered twice the normal rating on the meter. For Acros, I knew that the real EI was at least 100, and so I entered 200 on the meter. I then adjusted the lights to give a two stop difference. In this case the fill side got f/5.6 and 1/2 and the other side read f/11.5. That's a standard "low contrast" ratio. I set the camera on f/5.6 and took a picture. I took three more picture, closing down 1/3 stop each.

    For the next series, I upped the main light one stop. (3-stop difference.)

    Finally, for the last series, I upped it one more. (4 stop difference.)

    After I developed the film, I read it with a densitometer.

    My EI in each case was 125. (The black square of the chart read at least 0.10 above film base plus fog.) I read the white square on the main light side to check high light density. In the future, I'll set exposure for flash in the studio by setting my meter at 250 and set exposure according to the level of the fill light, trying to remember to apply bellows extension correction if needed. There will be a different development time for each lighting ratio. Thus we're back to the "meter the shadows for exposure and develop for the highlights" maxim.
    "Why can't we all just get along?" President Dale, Mars Attacks

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    ic-racer's Avatar
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    Re: Studio exposure/development test for black and white film illuminated with strobe

    "We all know that exposure predominately effects the darker areas of the scene, "

    Exposure change affects the mid areas the most. Toe and shoulder least.

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    Re: Studio exposure/development test for black and white film illuminated with strobe

    Sounds overly complicated. While I've never seen anyone use that method of metering, if it works, it works.
    Lighting with strobes becomes a lot easier with a dslr.

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    Peter De Smidt's Avatar
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    Re: Studio exposure/development test for black and white film illuminated with strobe

    It took me about 2 hours total to do the test, which includes driving to the studio, developing the film... That isn't much longer than a standard Zone System test. I now know the film speeds and development times for 4 different ratios, the most common ones I'll use, and I can extrapolate to others if needed.
    "Why can't we all just get along?" President Dale, Mars Attacks

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    Re: Studio exposure/development test for black and white film illuminated with strobe

    Agreed with Vinny.

    I too, am happy that this particular Methodology worked for you (at this time).
    But, it most certainly is not what *I* would call an 'empirical' method.
    --
    Peter, what now happens on an actual 'Shoot'...
    When your Subject Brightness Range is different than that of the Macbeth ColorChecker?

    Perhaps, this is now... 'Food for further Thought?'

    Best regards, -Tim.

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    Peter De Smidt's Avatar
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    Re: Studio exposure/development test for black and white film illuminated with strobe

    I have spent a couple weeks doing actual "shoots". I want'd to get more predictable results with varying lighting setups then given by the "try something and see" approach, just as one does with zone system testing for landscapes. In addition, I've been scanning the results of these shoots, and I'm investigating what negative density range produces the best results with my Cezanne. To do that it helps to be able produce specific densities....

    I only used the Macbeth ColorCheckers because, first, they were sitting right in the drawer. Second, they have a nice matte black patch and matte white patch. I only used the black patch on the chart illuminated on by the fill light and the white patch illuminated by both lights. Any matte black or white would've been fine.

    I have info now for a number of SBRs. So what's the problem again?
    "Why can't we all just get along?" President Dale, Mars Attacks

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    Re: Studio exposure/development test for black and white film illuminated with strobe

    >> I then adjusted the lights to give a two stop difference. In this case the fill side got f/5.6 and 1/2 and the other side read f/11.5. That's a standard "low contrast" ratio. I set the camera on f/5.6 and took a picture. I took three more picture, closing down 1/3 stop each.

    >> For the next series, I upped the main light one stop. (3-stop difference.)
    >> Finally, for the last series, I upped it one more. (4 stop difference.)

    Peter, as per above... You have now only changed your 'Lighting Ratios'.
    --
    Therefore, let's proceed with this 'thought' experiment further -- Okay?

    Pretend, that instead of photographed the ColorCheckers...
    You are now photographing 'say' two (2) Black Cats sitting 'side by side' on separate pieces of Black Velvet -- Each illuminated by their own 'lit' white candles (as per above).

    What would your results be?

    Why did your results change? Did your 'Lighting Ratios' change? (No).
    You have simply... Just proceeded with your testing once again -- As per above.

    Therefore what has now changed? Your Subject Brightness Range has now changed!
    (*Reflective Flash Meter readings... Would of course indicate this).
    Last edited by Taija71A; 31-Jul-2015 at 23:28.

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    Peter De Smidt's Avatar
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    Re: Studio exposure/development test for black and white film illuminated with strobe

    On one side, we'd have, in effect, a black cat in shade. On the other side we'd have a black cat in sun.
    The sbr depends on the subject, and also on the illumination.
    As far as I can tell, you don't like incident metering. That's fine, but it's what I'm going to use.
    "Why can't we all just get along?" President Dale, Mars Attacks

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    Re: Studio exposure/development test for black and white film illuminated with strobe

    What I don't understand here is if you change your lighting ratios, and then change the development to bring them back to "normal", hasn't the modified development essentially unchanged the lighting ratios and you're back where you started, except with possibly damaged local contrast because of less overall development?

    I'm not a big zone system fan anyway--the guy I worked for in high school had a string on his key light and one on his fill. That's how he set both the exposure and the ratios. I do the same thing now, but without the string. :-)

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    Re: Studio exposure/development test for black and white film illuminated with strobe

    Quote Originally Posted by Peter J. De Smidt View Post
    If I had a spot meter that worked with flash, I'd be all set, as I could do the same thing I do for a landscape with a subject in the studio. But I don't have one. I only have incident flash meters.
    No problem. An 'Incident' Flash Meter is just fine Peter!
    There is definitely no need to acquire a different Light Meter.


    Quote Originally Posted by Peter J. De Smidt View Post
    As far as I can tell, you don't like incident metering.
    I can 'happily' work with either a Flash Meter in 'Incident Mode' or 'Reflective Mode'.
    I have no real preference...
    --
    As long as you understand 'Lighting and Metering'... Nobody really cares how you choose to Meter -- Do they? All that really matters is:

    1). That your Light Meter is 'Accurate and Consistent'.

    2). That you are aware of the 'inherit' limitations in using an Incident Light Meter.
    (*Whether this be with Ambient and/or Electronic Flash)

    3). That you know how to interpret the results.

    and of course...

    4). The final RESULTS!!!

    Have Fun!

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