Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,327   Posts: 1,536,985   Online: 1206
      
Page 5 of 7 FirstFirst 1234567 LastLast
Results 41 to 50 of 64
  1. #41

    Join Date
    Mar 2011
    Shooter
    Medium Format
    Posts
    27
    Quote Originally Posted by wiedzmin View Post
    Christoph, I hope that you do not mind that I'm using your thread.
    @Tomasz, no i don't mind...it is rather a very good opportunity to learn and understand quite some things about film testing, etc......so thank you and bill for your input and time invested in this thread...

    @Bill,...considering flare...isn't it that Ralph's test is taking that in account so that the results are more "real" when exposing the test films...like flare from the lens and camera you use...should be considered...because "out in the field" you are using that same equipment taking actual photographs...?!
    Last edited by qualsound; 12-15-2013 at 05:50 AM. Click to view previous post history.

  2. #42
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,226
    Images
    46
    FIRST AND MOST IMPORTANT... I SEE WHERE THE DISCREPANCY CAME IN.

    You manually overrode the Average Gradients that are properly calculated on "Input Data" page, when you got to each Curve page.

    Cell L 48 - on every page "Curve 1" "Curve 2" "Curve 3" "Curve 4" "Curve 5" does not match the calculated cell K 48.

    For specific example, Ralph calculated 0.59 for 11 minutes where I calculated 0.6 !!!!!

    Were you aware of this adjustment? Or does it contain default values from the published spreadsheet?

    If it contains default values from the published spreadsheet... Then my long-standing puzzle has been solved!!!


    Back to the test design...

    It's better science to eliminate variables from testing. Flare is a variable that can easily be eliminated from the experiment by placing the Stouffer scale in contact. But I didn't come here to harp on that.

    The bigger problem flare causes IN CAMERA TESTS... Is that you just can't get anything useful from the steps denser than 2.0

    I have another suggestion. Only take the results from steps with densities 1.60 and less. Make series' of exposures. One just as you did. Another shot with 4 stops more exposure. For the numbers you enter in the spreadsheet, only take the "top half results". Ignore any densitometer readings from the test film where the step wedge density was above 1.60 because you can't trust it. But because you have a high range and a low range, together you should have a full range test.

    ACTUALLY, YOU ALREADY HAVE THE LOW RANGE, BECAUSE YOU UNDEREXPOSED FOUR STOPS!...
    -Just put it together with another test where you expose for the High Range.

  3. #43

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    @Christoph - thank you

    @Bill, thank you for your help and your time. I really appreciate it.

    Cell L48 yes I made those changes , it is according to manual Ralph provided with his spreadsheet (I was trying to do everything exactly like in WBM book and link to pdf). http://www.waybeyondmonochrome.com/W...Evaluation.pdf page 5 right column in the middle. It looks like Christoph did the same.
    quote from the pdf:
    "Start by visualizing a smooth curve through the existing
    data points in fig.5a. Then, imagine an extension of that
    smooth curve all the way up to the right cross hair (Dmax).
    Now, adjust the average gradient value in cell ‘L48’ slightly,
    trying to improve its current position until it intersects with
    your visualization of that smooth extension. This may need
    a little practice, but as you will see, it does not have to be
    perfect to significant improve the following calculations."



    Is there any way you can contact print a step wedge?
    I have only 35mm and 120 step tablets. For contact printing, I'm guessing I would need 4x5 and maybe cut it in half and tape it so it will fit on roll film length wise? What light source should I use for exposure?
    For my tests I used something like that http://www.pentaconsix.com/C436_29.jpg, http://www.pentaconsix.com/C436_32.jpg but with Hasselblad 500cm. In addition I placed collapsible diffuser between camera and the flash.

    Back to the test design...

    It's better science to eliminate variables from testing. Flare is a variable that can easily be eliminated from the experiment by placing the Stouffer scale in contact. But I didn't come here to harp on that.

    The bigger problem flare causes IN CAMERA TESTS... Is that you just can't get anything useful from the steps denser than 2.0

    I have another suggestion. Only take the results from steps with densities 1.60 and less. Make series' of exposures. One just as you did. Another shot with 4 stops more exposure. For the numbers you enter in the spreadsheet, only take the "top half results". Ignore any densitometer readings from the test film where the step wedge density was above 1.60 because you can't trust it. But because you have a high range and a low range, together you should have a full range test.

    ACTUALLY, YOU ALREADY HAVE THE LOW RANGE, BECAUSE YOU UNDEREXPOSED FOUR STOPS!...
    -Just put it together with another test where you expose for the High Range.
    sorry it is my fault by using Christoph's thread but above suggestion is for Christoph's or my test?


    thank you
    Tomasz
    Last edited by wiedzmin; 12-15-2013 at 12:04 PM. Click to view previous post history.

  4. #44
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,226
    Images
    46
    OK so the adjustment caused the discrepancy.

    I also had to do some visualization on paper to get CI. You can see my dashed lines reaching up to the letter "C" in the right margin.
    But the "extensions" I drew were fairly short. You got the majority of the data needed to determine "CI".

    For now, I recommend trusting the Average Gradient as-is and not adjusting.

    Next tests when you have more data, you won't need to adjust Average Gradient.

    Since you went to the trouble to setup a camera according to Ralph's instructions, go ahead and keep using that setup.

    The one improvement from this thread I recommend going forward is to make two separate exposures, one with three stops more exposure than the other.

  5. #45
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,226
    Images
    46
    Tomasz,

    My comments regarding adjustment errors relate to Christoph's HP5 data that I graphed on paper.
    His figures were significantly different than mine, while the calculated results are very close.

    Your adjustments (HC 110 and Acros 100) are minor in comparison.

  6. #46

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    Quote Originally Posted by Bill Burk View Post
    Tomasz,

    My comments regarding adjustment errors relate to Christoph's HP5 data that I graphed on paper.
    His figures were significantly different than mine, while the calculated results are very close.

    Your adjustments (HC 110 and Acros 100) are minor in comparison.
    thank you,

    In my case do you recommend? :
    the one improvement from this thread I recommend going forward is to make two separate exposures, one with three stops more exposure than the other.
    Do you mean by that exposing 10 rolls of film?

  7. #47
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,226
    Images
    46
    Quote Originally Posted by wiedzmin View Post
    thank you,

    In my case do you recommend? :
    Do you mean by that exposing 10 rolls of film?
    Wow that's a lot of film for testing. I normally test on sheet film and fit three "tests" on a single sheet of film.

    And for 35mm, I add the test at the end of any particular unfinished roll that might be in a camera.

    But in a roll camera can't you take two shots and then cut it off and develop it for one of the tests?

  8. #48

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    I never tried that but I guess it will work. What about taking 6 exposures (120 film) + 6 exposures (+3 stops )? I could cut roll in half before loading it into reels. This way I will use 5 rolls but have 10 tests. Will developing only half of the roll affect test accuracy, I would normally develop full roll in the same volume of developer?

    I was under impression that it is better to perform film test using actual equipment which is going to be used to take photos based on film test. You pointed out flare problem but would not that flare exists in "real" photos taken with that equipment anyway?

    If I understood your suggestion correctly:
    I should for each developing time (4, 5.5, 8, 11, 16) read steps up to 1.6 density from normal exposure and above 1.6 from those with +3 stops of exposure? Enter values to the spreadsheet and do not modify AG for each curve.
    Did I understand it correctly?

    thank you

  9. #49
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,226
    Images
    46
    I've reeled a 35mm roll with nicks at each test and then pulled and ripped off a strip when I reached pre-planned minutes. It'd be easier to do 2 reels with 2 strips of film reeled onto each reel, already cutoff. Use the normal volume of solution. Actually it does matter "where" in the reel a test is placed, but the difference is small enough to not be important. I have done tests where I graphed several strips from a single roll of 35 mm film. Each curve differed slightly from the others - despite being on the same reel and developed for the same time. At some point you have to accept these minor variations.

    ---

    You can estimate flare and add it back in when you interpret the results.

    ---

    I'm suggesting that you don't even bother reading any steps past step 16 on your 30-step test wedge because flare gives the entire sheet of film an exposure near what step 20 gets, which ruins the samples below step 20 and interferes with the accuracy of the steps from 16 to 20. But from steps 1 to 16 flare doesn't affect the exposure much.

  10. #50

    Join Date
    Mar 2011
    Shooter
    Medium Format
    Posts
    27
    Quote Originally Posted by Bill Burk View Post
    Tomasz,

    My comments regarding adjustment errors relate to Christoph's HP5 data that I graphed on paper.
    His figures were significantly different than mine, while the calculated results are very close.

    Your adjustments (HC 110 and Acros 100) are minor in comparison.
    Bill thank you for clarifying.
    I adjusted the average gradients of each curve in cells L48, like tomasz said, according to ralphs instructions in the pdf file accompanying the excel spreadsheet. It was my intention, that the curve would intersect the crosshair... i see now that it is better to leave these cells untouched and let the spreadsheet do the calculating.

Page 5 of 7 FirstFirst 1234567 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin