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Thread: Multiple exposures / reciprocity with Velvia 100F

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    Apicomplexan DrPablo's Avatar
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    Multiple exposures / reciprocity with Velvia 100F

    I'd like to reproduce a very interesting photo that I took digitally.

    It requires 5-7 separate exposures of about 30 seconds each. I quite laboriously combined them in PS when I shot it with my DSLR. Now I'd like to do the same thing with my 4x5 using multiple exposures on a single sheet film.

    I have oodles of Velvia 100F lying around, and I think it would work very well for this kind of shot. But we're talking about a total exposure time of 3-5 minutes. So calculating exposure will be tricky, and I worry that I'll run into color shifts.

    Do you think this is reasonable to try with Velvia 100F, or is there a better film for this purpose? And how will I calculate the exposure -- if I plan on, say, 8 exposures, do I just meter in Tv mode for 4 minutes and divide it into 8 separate shots?

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    Re: Multiple exposures / reciprocity with Velvia 100F

    Astia needs no correction for reciprocity up to two minutes.

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    Kirk Gittings's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    My experience from years of doing multiple exposures seems to indicate that reciprocity is not cumulative. For instance the reciprocity correction for 4 one second exposures is not the correction for a four second exposure.
    Thanks,
    Kirk

    "When did photography become a desk job?" Kirk Gittings 2009

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    Apicomplexan DrPablo's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    But if even a 30-second exposure can have reciprocity failure, then what about several 30-second exposures?

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    Kirk Gittings's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    Say 4/30 second exposures. Each 30 second exposure has a calculated RF. But it is different than calculating the RF of a 120 second exposure.


    The real difference comes into play with the marginal exposures (where RF just starts to come into play with a given film). A film may have no reciprocity failure problems at 10 seconds say, but big problems at 60 seconds. In this scenario 6/10 second exposures will still have NO RF, because RF is NOT cumulative, even though the total exposure is 60 seconds. Does this make any sense? This has been my experience that has guided me for many years in this sitution with many films.
    Last edited by Kirk Gittings; 17-Aug-2006 at 16:33.
    Thanks,
    Kirk

    "When did photography become a desk job?" Kirk Gittings 2009

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    Apicomplexan DrPablo's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    Yeah, that makes sense.

    So say I calculate exposure for 8 30-second shots; i.e. 4 minutes of exposure time will be a proper exposure, aggregated over 8 separate clicks of the shutter.

    It would then be fair to assume that reciprocity would only be an issue insofar as it might happen in 30 seconds, rather than 4 minutes?

  7. #7

    Re: Multiple exposures / reciprocity with Velvia 100F

    I think what Kirk is trying to say is that RF does not have a linear behavior, if I am correct then he is right. In simple terms light needs to have enough energy to remove electrons from the silver crystal, when we find ourselves in the recirpcity area what is happening is that the light does not have enough energy to "push" the electron. The electron gets exited, but immediately falls back to it's energy level, thus we need to give the light more time to keep "pushing" the electron out of the energy level. The lower energy the light has, the more time we need to give it to push the electrons so that they dont fall back, as I said this is not a linear relationship.

    In these situations what needs to be done is to calculate the RF for the TOTAL exposure time and then if you wish you can break it up in parts. For example if you have an exposure that requires 4 minutes, and then when you add RF it turns out it needs 15 minutes, you can break the exposure in 3 five minute exposures. You cannot say I will make 4 one minute exposures and calculate the RF for a 1 minute exposure, you will get an underexposed sheet.

  8. #8
    Robert M Teague
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    Re: Multiple exposures / reciprocity with Velvia 100F

    Here is the datasheet for Velvia 100F: http://www.fujifilmusa.com/JSP/fuji/...AF3-148E_1.pdf

    No compensation is needed to 1 minute, with less than one stop loss to 8 minutes.
    Robert M. Teague
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  9. #9
    Kirk Gittings's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    Jorge, sort of. Lets say at 4 sec there is no RF on a film. 4 exposures at 4 sec will still not have RF.
    Thanks,
    Kirk

    "When did photography become a desk job?" Kirk Gittings 2009

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  10. #10
    Kirk Gittings's Avatar
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    Re: Multiple exposures / reciprocity with Velvia 100F

    what is happening is that the light does not have enough energy to "push" the electron. The electron gets exited, but immediately falls back to it's energy level, thus we need to give the light more time to keep "pushing" the electron out of the energy level.
    I believe this phenomena repeats itself anew with each separate multiple exposure with no memory or cumulative RF affect. I have used this approach successfully for years on daylight chromes of all types (EPP EPN Velvia Velvia 100F etc.).
    Thanks,
    Kirk

    "When did photography become a desk job?" Kirk Gittings 2009

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