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  1. #1
    Pastiche's Avatar
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    Densitometer + Dektol 1:9 + ERA 100 + Step Tablet

    What could these things possibly have in common? Me.

    I'm working through my first ... er.. attempt at using my densitometer (xrite 810) to get "perfect" development times.

    Here is where things take a left hand turn:

    I'm using Dektol. 1:9

    I'm also using an unknown film (ERA 100) - which, despite any fears I may have about their QC, I'm quite certain that there is less variation in THEIR process than in my own.. so if there ever were to be something wrong, I'd suspect myself first. (even though I'm a fairly meticulous lab tech)

    So... using a film + developer combo that is essentially "unknown" pushed me to pick up a densitometer.

    NOW. . . I had some issues copying the densitometer in camera (the light behind the tablet, even though being bounced from a diffuse white surface {card}, was not even. So, the steps are meaningless b/c the light seen through them is not constant)

    I've decided to try exposing the film to the Stouffer 21 step tablet in a contact print frame.

    I'll be putting a lens with a copal 1 shutter in the enlarger head, and metering the exposure via .. .

    Yeah.. via....

    That is where my questions are.

    how the hell do I meter this situation?

    Do I spot meter the step 10 (let's say, I put the tablet on a white card, spot meter step 10?)

    Do I take an ambient reading just above the contact frame? (I'd raise the enlarger head all the way up to give me the best chance of getting a reading where the thickness of the meter itself does not significantly change the distance of the film/light source when compared to the point metered/light source)

    Do I put the spot meter lens under step 10 and point it at the lens??

    er..

    yeah. What?

    Thanks for your thoughts on this.
    I'm not afraid of burning up some film - but I AM considering that what I might really need to do is to go back to the studio and set up the step tablet again and shoot it in camera (compensating for bellows extension... yes)

  2. #2

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    Quote Originally Posted by Pastiche View Post
    I'm working through my first ... er.. attempt at using my
    densitometer (xrite 810) to get "perfect" development times.
    For film I use an uniformly lighted large gray board. With
    camera in position I expose a number of frames at one
    stop increments. My Tobias TB+ does the reading.

    For paper, the step tablet as though a negative to be printed,
    is placed in the negative carrier. Dan

  3. #3
    Pastiche's Avatar
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    OK... so here are my first two curves.

    Film: ERA 100
    ISO used: 50
    Developer: Dektol, 1:9
    Jobo processed, CPP2, 20 degrees Centigrade (68F), 5min.

    One sheet of film was exposed for .3", the other for .1" under a condenser enlarger, in a contact frame.

    To determine exposure I did the following:

    Set the meter to 50ISO, f/1.
    opened up the enlarging lens all the way.
    focused the lens on the neg. carrier (which had no neg in it, used the edges of the carrier for focus)
    adjusted the height of the head until the meter told me to use 1/2" exposure time.
    The meter was held under the contact frame's sheet of glass while metering.
    Ambient metering mode.


    I actually did three sheets, one at .5", one at .3", and one at .1"
    Of the three, I only measured the last two, as they "looked best" . . . and they both had two or more "clear" steps after step 21 on the Stouffer tablet.

    It appears to me, from looking at these curves, that I need to dilute my chem out a little bit more (shouldn't that lower the slope of my curve? i.e. change my contrast index?)

    I'm still fuzzy on how to determine film speed from the curve, particularly as I'm fuzzy on how exactly to meter the *blipping* exposure to begin with.
    AND - I'm not sure that using the enlarger's timer at such short times is effective. In the future I think I'll try to stop down till I get the exposure time close to one second.

    Later on I'll measure and generate a curve for the third sheet of film, that one exposed to .5", which I have not included here.

    Ideas? Suggestions? What am I missing here?

  4. #4
    Pastiche's Avatar
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    Oh.. I forgot the mention a few things:

    a) my "film base plus fog" seems to be ... .20 NOT .10 as I've seen suggested as the "right" measure. Might this be because of the characteristics of Dektol? Would diluting the solution help lower FB + F ?

    b) the max values on my step wedges were : 1.94 for the one exposed to .3", and 1.75 for the one exposed to .1" ..... the FB+F numbers for both sheets were .01 apart, which I assume to mean they are virtually identical.

    Again, the meter told me to use .5" exposure, but that sheet looked WAY dense to my eye.... I'll grab the numbers from it latter on.

    Questions -

    The total range of densities seems to a) start high and b) end even higher.
    I've read that the "goal" is to push the tones around till they are separated by 1.30 units.
    I'm thinking that what I need to monkey with is the dilution & times... not the ISO.
    Does it seem like that to you as well?

  5. #5
    ic-racer's Avatar
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    Nice curves. It is perhaps futile to determine EI from H&D curves unless you have a calibrated sensitometer. The best exposure for the step wedge, in that case, is one that produces an acceptable range of values to plot. (Best way to get EI is just expose a frame to a uniform source at zone I and see that it is 0.1 log d).

    The gold standard for both exposure and development is a good looking print. So, I work back from that. I determine a development time that produces a good print by trial and error. Then I determine the contrast index of that setup (by making the curves, as you are doing). I use this contrast index as a starting point for my next 'unknown' film developer combination.

    So, again, you have what looks like appropriately constructed curves, but they don't mean anything until they are matched with good prints.

  6. #6
    Pastiche's Avatar
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    Thanks IC, for the input.

    Yeah.. part of my plotting these curves is that I want to know in which direction to take my process.... I'm using two unknowns, a paper developer as film developer, and a film that has virtually no process info available for it (besides some VERY broad guidelines).

    My prints have been a bit too contrasty, and much to my surprise, sort of lacking in the deepest shadow details (like... a black belt as it rounds off to the shadow side of the figure, even while shot outdoors in open shade) .. . .

    Plus, every time I make changes to my process I feel like I'm sort of driving around in the dark not knowing what to expect (or to what degree to expect it).

    And.. finally, I guess I'm one of those nerds who just needs to KNOW . .. does that make sense? I'm not a cabinet maker, but if I were to build cabinets, I'd want to really UNDERSTAND the construction process. I expect that in the long run I'll be able to pick up strange films & developers and get to the kinds of results I'm hoping for via a minimum of trial and error. Also - I'm hoping that once I know how to do these tests efficiently, I'll be able to minimize lost materials and time when "trying to find" a sweet spot in the film/developer/paper/developer processes.

    Idunno... maybe I'm just a control freak.
    I do follow you though - the finished product IS the gold standard.
    If I'm at point A with my process, and wish to get to point B (let's say, changing the contrast index, or reaching a particular contrast index), I'd like to learn how to do it in as few steps as possible (vs. trial & error).

    I've found a .pdf by Kodak that is over the top on sensitometry (at least for me, at this time).
    Here's the link to the publication titled Basic Photographic Sensitometry Workbook

    I've also found a page that describes development testing in this way, and includes a link to a spread sheet app. that takes in your density readings and spits out the curves I've been posting here. Also giving projected times for development at N +/- 1,2 & 3 Here

    Here is a screen grab of the curves I got from developing last night.
    [IMG][/IMG]

    I'm STILL a little lost on why my lowest readings are so high. .20 as the lowest density? I guess I'm not sure if I'm getting light going through even the darkest step on the Stouffer tablet, or if this is just an artifact of my developer's properties.... Next time I develop I'll include an unexposed sheet straight from the box and see what that gives me.

    In that Kodak pdf on sensitometry is states how to determine if the film has been "properly developed" . . .
    Now, caution about "technically correct" vs. artistically apropos aside, I'd like to know that I'm "technically" getting it right before I start wandering off into the wilderness of expressiveness. I'm not short on the latter, but I do need a known starting point from which to depart.

  7. #7
    Pastiche's Avatar
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    IC - I forgot to say: my densitometer is calibrated (from a step wedge, notated by Xrite)

  8. #8

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    Quote Originally Posted by Pastiche View Post
    Oh.. I forgot the mention a few things:

    a) my "film base plus fog" seems to be ... .20 NOT .10 as I've seen suggested as the "right" measure. Might this be because of the characteristics of Dektol? Would diluting the solution help lower FB + F ?

    ...?
    The film base + fog density can be anything. The confusion here is that the speed point for film is measured at a density of 0.1 above the film base + fog level. High fog is usually an indication that something is wrong, however. Sometimes it shows up with old film, and sometimes it indicates a mismatch between the film and developer. Sometimes it is OK.

  9. #9
    Pastiche's Avatar
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    Thanks nworth.

    I'll keep that in mind as I go on down the road of testing this combo that I have on hand.

  10. #10
    Stephen Benskin's Avatar
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    It looks to me like the gradient is around 1.00. You might want to adjust the processing some before settling on an exposure time.

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