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  1. #1

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    Film speed testing question using waybeyond excel sheet

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ID:	63432Hi All,

    Need a little help here. I am using Ralph Lambrech's spread sheet to determine my film speed.

    A 21 step wedge was contact printed Hp5+ at f/8 .7 seconds in Xtol 1:1 @20c for the 4, 5.5, 11, and 16 minute intervals.

    Could someone who is familiar with this procedure look at my graphs and tell me what is wrong? I am thinking my exposure is still too short as I am missing too many data points in the shorter development times?

    I have a macbeth TD500 and I zeroed using the instruments light source. A calibrated step wedge indicates measurements are accurate.

    Any help would greatly be appreciated.

    Thanks


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    Last edited by padraigm; 01-31-2013 at 12:58 PM. Click to view previous post history.

  2. #2

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    Wow. When did photography become a freakin science project?

  3. #3

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    Quote Originally Posted by pawlowski6132 View Post
    Wow. When did photography become a freakin science project?
    Since 1890, when Hurter and Driffield invented sensitometry and densitometry.

  4. #4

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    I've not used the spreadsheet you have, but it looks to me that you don't have enought exposure on your 4 min time for the sheet to calculate a valid gradient. Note that the 4 min point on the time vs. gradient graph is way up above the over points off the graph. It looks like that point is calculated to equal 1.90 gradient. We all know it should be less than the 5.6 min gradient.

    I suggest rerunning the 4 min test and give the film about 4 stops more exposure to get more steps in the wedge to have usable density.

  5. #5
    Bill Burk's Avatar
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    Looks like your 8 minute time came reasonably close to what I call normal, the curve that most closely fits ASA specifications. Since the spreadsheet shows that near 0.62, that confirms your test is sane.

    As Kirk says, 4 stops more exposure would help for the 4 minute test. Next time you do a complete series, I would give 2 stops more exposure to all.

    Of course it would have been better if you could see all the data in the highlights. But for darkroom printing, you only need to see what exposures gives you highlight densities around 1.00 to 1.20. You have enough information to make informed decisions about how long to develop your film.

    Apart from the 4 minute test, the rest of the gradients look good.

  6. #6

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    Hmm. Someone forgot to tell 99% of the brilliant photographers past and present.

    The above is totally unnecessary.

  7. #7
    Stephen Benskin's Avatar
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    Quote Originally Posted by pawlowski6132 View Post
    Hmm. Someone forgot to tell 99% of the brilliant photographers past and present.

    The above is totally unnecessary.
    That's right people. You should know that by now. It's YOU push the button, KODAK does the rest. Duh.
    Last edited by Stephen Benskin; 02-01-2013 at 07:44 AM. Click to view previous post history.

  8. #8

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    Sorry

    Quote Originally Posted by Stephen Benskin View Post
    That's right people. You should know that by now. It's YOU push the button, KODAK does the rest. Duh.
    You're right. ,sorry people. Fluency in chemistry, sensitometry, electrochemistry, etc is a prerequisite to producing great photographic art.

    I'm so stupid. My apologies.

  9. #9

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    tl;dr: stfu, pawlowski

    Pawlowski, without people that treated photography as "a freakin science project", you would have NO materials with which to make your own images. No one is claiming that everyone needs fluency in all the scientific disciplines impinging on photography to create great photographic art. What is necessary for anyone to create great photographic art (or workaday snapshots) is that some practitioners have that fluency, to enable the production and improvement of materials.

  10. #10

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    Kirk, Bill and everyone else thank you. Even you pawlow, haters gonna hate. I figured that was the case with not enough info in the 4 min development data set. Smoothing out the curves helped. I am finding I need way more exposure that what has been typically posted to run tests like this. I must say it's quite easy and fast once you have an exposure that works. The data pretty much came in line with what I came up with prior to having a densitometer. It's nice to see the + and - also in one go. I am primarily going to use this for alternative printing in the future and want to have some sort of "quantification" so as not to waste expensive materials. Thanks again.

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