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  1. #81
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    Heroic work for us Mark.

    PE

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    Hi Mark - was thinking - are you able to share the curves Kodak sent you? It would be cool to see what characteristic curves actually look like when they come directly out of Kodak's lab.

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    Michael, they do post curves on-line, but geez, I've got a few here that I've never scanned in.

    Each division plotted them differently though, so it might surprise you to compare mine with the on-line curves to the ones sent to Mark.

    PE

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    PE, I mean the detailed, full curves that come out of their auto-densitometer or whatever they use nowadays, as opposed to the highly simplified stuff they post in the tech pubs.

    Edit: PE if you're ok posting some of the curves you have, I'd love to see them. As a fan of Kodak, Ilford etc. I've just always wondered what the "real deal" looks like (compared with the homemade stuff the rest of us come up with). What is the preferred scaling on the axes, preferred units etc.
    Last edited by Michael R 1974; 05-19-2013 at 03:26 PM. Click to view previous post history.

  5. #85

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    Michael,

    The best curve didn't have numbers on the X-axis, which would have been great for calibrating log-E.
    The other was a group of six or so curves, all superimposed, forming a band in which you could see variations from each other. It showed that Kodak's manufacturing was staying within reasonably tight tolerances, but that's still not what we want for comparing with our own work.
    Bottom line: I have no curves to post that would help us with our own measurements. But I can post what I got if you're still interested.

    Mark

  6. #86

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    Hi Mark - if it isn't too much trouble to post them I'd still be curious to see them.

    Michael

  7. #87
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    Quote Originally Posted by Michael R 1974 View Post
    Hi Mark - if it isn't too much trouble to post them I'd still be curious to see them.

    Michael
    I would also be curious to see them, Mark. Thank you!
    Shawn

  8. #88

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    That's two requests, and others are probably interested too, so here goes.
    The curves below show the lower- and upper-contrasts for all recent batches of TMY2. It's clear that nothing has changed in the last few months:

    Click image for larger version. 

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    And here are the curves of recent batches. They all fall within a reasonably close band, so once again, no problem:

    Click image for larger version. 

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    As a result of my query, Kodak pulled some sample films from storage, exposed and developed them, and plotted the above curves. I was hoping they would include samples purchased from the open market, but I'm guessing the curves above convinced them that everything is fine.

    Mark

  9. #89

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    Mark/PE - what increments do you suppose the tick marks are on the log exposure axis?

    While the curves all fall within a resonably close band, at least two of them appear to show the type of curve I got - ie a slight dip and then an increase in contrast (at around the same densities I observed).

    Again, nothing to worry about from a user standpoint, but I'm glad you posed these because they show us there will always be some variation in manufacturing - however small. Even the base fog density seems to move around slightly, and as long as Kodak is ok with it, I'm ok with it.

    I think this is important because there are people who try to calibrate their home testing to the n'th degree of precision, and they'd also call a slight change in curve shape catastrophic. These curves show that even disregarding all the variables and errors involved in home processing, there will still be some small degree of variability inherent in the manufacturing process. We might never know for sure on any given day precisely which curve we have, but they are all close enough.

  10. #90
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    Thanks for posting these, Mark!

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