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Thread: Reciprocity Timer 1.0

  1. #11
    Do or do not. There is no try.
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    Jan 2007
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    733

    Re: Reciprocity Timer 1.0

    Hi Stef,

    The times you list in the "Metered Exposure" column differ slightly from those that you'd read off a light meter dial, for example 15sec instead of 16sec. How did you choose the times?

  2. #12

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    Jan 2009
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    Re: Reciprocity Timer 1.0

    I think the "bell" at the end is WAY too loud- the iphone volume doesn't lower it. I'm embarrassed to use it in public. Please either drop it or make it user-controllable.

  3. #13

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    Re: Reciprocity Timer 1.0

    Does anyone have a table of verified reciprocity times for various films (e.g. TMY2)?

    I have not yet downloaded the app because it does not include my primary film. I wonder if it could include user programmable tables that feed the controls/dials on the app?

  4. #14

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    Feb 2011
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    Re: Reciprocity Timer 1.0

    Thanks for all the suggested improvements guys. I will certainly take those suggestions on board and make some changes. You can expect an update soon.
    The times I selected for metered exposure were really just arbitrary so I will look at making them more closely match a spot meter.
    I'll turn down the bell. Sorry! I'm a bit deaf....
    I will also look at changing the slider to provide some finer control. I have a lee big-stopper. Hence the 10 stops...
    I did want to make it possible to add your table but this is complex and might be a while away.
    I will also try to add some more film types while I am doing an update. If anyone has reliable references for formulas I am keen to see them. One issue I have found is that there are many conflicting tables and formulas...
    Thanks for the feedback guys and thanks for trying it out. I'll see what I can do to address the suggestions!

  5. #15

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    Re: Reciprocity Timer 1.0

    I went ahead and downloaded the app. I think it has good potential.

    Apart from adding additional films, some additional features might include:

    A toggle switch to calibrate the slider in 1/10, 1/3, 1/2, 1 stop increments

    A link to tables with filter factors and stops including the math for combining filters

    A link to bellows compensation information, and perhaps a second slider for bellows extension adjustments that could be enabled/disabled.

    If it had Tmax films plus the above features I would be willing to pay more also.

  6. #16

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    Jul 2008
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    Re: Reciprocity Timer 1.0

    I bought the app too.

    What would be a great addition is the development compensation that matches the chosen exposure.
    ie: A 12 second metered exposure requires X time and -8% dev. etc.
    That would be perfect.


    I like Jeroldharter's idea about a bellows extension table.

    I think in North America, it has to have T-Max tables to fly, T-max really seems to the number once choice of film here.

    I agree the bell is a little loud if you are in a public place. I imagine shooting the interior of a cathedral.
    For now, you can hold the phone so the speaker rests on the tip of your baby finger and it cuts the noise by 80 percent.

  7. #17

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    Re: Reciprocity Timer 1.0

    Hi all. I have submitted an update to the app to Apple for approval. Hopefully it will hit your phones in the next week or so.

    I have added a bunch of films - including Kodak TMY, TMX, Velvia 100, and Efke. Among others. The maths for the black and white films is now largely based on the Gainer method as discussed here (thanks to SMBooth for putting me onto that article).

    The Efke calculations are based on adding 1/3 rd of a stop to 10 secs, 1/2 stop to 100 secs and 2/3 of a stop after that.

    I also messed with the Ilford math (splitting it out into separate films and using the Gainer method). The returned data for HP5+ is now a very close match to Ilfords published charts.

    Please be aware that I don't personally shoot all of these films so I have no way to verify the calculations will result in correct exposure or negative density. If the numbers you get don't meet your real-world experience please send me your data tables and I'll try to make the required adjustments.

    I have also added the ability to adjust the slider by 1/3, 1/2 or 1 Stop increments.

    I also tamed the loud bell and made sure it adjusts with the volume control as expected.

    I like the bellow extension suggestion - but I only shoot wide angle and have never needed to calculate it. If someone can give me a definitive reference I'll look into it.

    Thanks again for giving the app a try. And for all the great suggestions. Some of the more complex ones might take a little longer to implement but I have certainly taken them on board.

  8. #18

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    Re: Reciprocity Timer 1.0

    Those are excellent and quick updates.

    For extension factor:

    Bellows length squared/focal length squared=exposure factor

    Example:

    Extension = 300 mm
    Focal length = 210 mm
    Extension factor = 90000/44100=2.04

    So the extension factor is ~2, or 1 stop.

    A metered exposure of 1/4 sec would then be 1/2 second.

  9. #19

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    Re: Reciprocity Timer 1.0

    Thx! I have implemented 2 sliders. One for extension and one for focal length. This seems to work well but I am wondering what the highest values should be? I have implemented it with 10mm to 500mm range. Does that seem right?
    I can have this feature included in the current release which should then cover off on all the main requests so far.

  10. #20

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    Re: Reciprocity Timer 1.0

    For large format, 90 - 600 mm should cover. I think Olympus made a 35mm macro for 35mm film.

    So 35-600 should cover film based scenarios.

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