Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,990   Posts: 1,524,135   Online: 1112
      
Page 1 of 4 1234 LastLast
Results 1 to 10 of 38
  1. #1

    Join Date
    Jan 2008
    Location
    Sarasota, FL
    Shooter
    35mm
    Posts
    921

    Massive Spectral Density Comparison of Films

    Another project from the depths of the lah-bor-a-tree on the bayou.....

    From the intro: "I’ve started getting intrigued with “Spectral Density Curves” for films. Is this topic the missing “secret” for film behavior? Is it the background for the H&D curves that we spend so much time looking at and deriving - inadequately informed - conclusions? Is this the criteria why some films seem so wonderful and others suck? "

    A look at the 20 35mm films from all of the major companies.

    Thanks and a tip of the hat to D F Cardwell, whose comments got me thinking. And wondering.
    Attached Files

  2. #2
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,171
    Images
    20
    I also think spectral sensitivity is a pretty important factor that most people ignore. It's the main reason I don't care for T-max films--their response is too linear, like B&W video.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  3. #3

    Join Date
    Nov 2003
    Posts
    621
    Quote Originally Posted by David A. Goldfarb View Post
    I also think spectral sensitivity is a pretty important factor that most people ignore. It's the main reason I don't care for T-max films--their response is too linear, like B&W video.
    What we all need to remember is that the same film and a different developer combination can generate a dramatic and vastly different density / exposure relationship from each other.

    T Max 400 in Xtol or Pyrocat at regular dilutions and processing is as you said, a straight 45 degree line.

    Dilute Pyrocat with T Max 400 utilizing stand or semi stand process generates an extended long toe and an emphasized S shoulder to such a degree that you would swear that this could not be the same emulsion. I am sure that there are many other examples that fit this model.

    As a result I am convinced that photographers that really know their materials can make quality photographs with virtually any film and developer combination. Looking at a graph is "interesting" but prints are the only thing that really matter.

  4. #4
    keithwms's Avatar
    Join Date
    Oct 2006
    Location
    Charlottesville, Virginia
    Shooter
    Multi Format
    Posts
    6,079
    Blog Entries
    20
    Images
    129
    Interesting thoughts, and yes, the spectral sensitivity curves are certainly something we don't spend enough time looking at. I try to raise this issue whenever we discuss filter factors and tonal contrast / separation.

    P.S. I'll just add, for what it's worth, that after some initial forays into UV photography, I think panatomic x and type 55 are some of the most UV-sensitive films still in use. I suspect that their sensitivity remains high well down into the 300s. I'll be doing some tests at ~325 in the coming weeks.
    Last edited by keithwms; 07-23-2008 at 02:08 PM. Click to view previous post history.
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  5. #5
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,171
    Images
    20
    Michael, you're talking about the H&D curve, which shows the relation between exposure and density, and I'm talking about the spectral sensitivity curve, which shows the film's sensitivity to different colors of light. Developer choice doesn't change the spectral sensitivity of the film.
    Last edited by David A. Goldfarb; 07-23-2008 at 02:20 PM. Click to view previous post history.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  6. #6
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,935
    Images
    65
    Spectral sensitizers can be development and fog inhibitors, desenstizers to blue light, and have a number of other properties. It is the total combination of emulsion, sensitizer and other addenda that make up both the wavelength that a film is sensitive to and the characteristics of that film.

    A case in point is a sensitizer that can be a green sensitzer for one emulsion and a red sensitizer for another. It is based on the emulsion, not the dye. A second dye can be a red sensitizer that leaves residual blue sensitivity, and another can repress blue sensitivity. And a third dye can be a super sensitizer giving huge boosts to an emulsion speed but imparting no special spectral sensitivity.

    Nothing substantive can be derived from the data you refer to other than the exact sensitivity of the given film itself.

    Much data on this is found in the chapter of Mees and James to which Paul Gilman contributed.

    PE

  7. #7
    keithwms's Avatar
    Join Date
    Oct 2006
    Location
    Charlottesville, Virginia
    Shooter
    Multi Format
    Posts
    6,079
    Blog Entries
    20
    Images
    129
    I agree with David and I think what is seldom appreciated is that:

    - spectral (wavelength) sensitivity can be a major player in tonal separation and contrast

    - stated filter factors are quite arbitrary around the edges of the sensitivity spectrum; you have to convolve the lighting spectrum (~colour temp) with the film sensitivity spectrum to get reliable numbers

    - no matter what the manufacturer's stated toe and knee look like, you don't know from the H&D curves what actual highlight and shadow curves you're going to get unless you again consider the actual lighting spectrum used for your shot and the film sensitivity spectrum. A pan film can deliver an image that is tonally contrasty or it can be blah flat... with the same developer and the same dilution and exposure time and everything, just by shooting through a colour filter. Extreme example: rollei R3 unfiltered, Rollei R3 red filtered. Please ignore the clouds in the sky, I am not talking so much about the dehazing effect of a red filter, but rather how the wood and grass tones are rendered, which has nothing to do with haze or Rayleigh scattering.

    David I don't know if this is what you meant, and I don't mean to put words in your mouth, but when you said tmax's response is too linear for your taste, I took that to mean too linear in overall wavelength sensitivity, which is an issue I see in these R3 test shots. My feeling is that tones simply don't separate well at all unless a filter is deployed.

    If a filter selects out that wavelength range that coincides with a big change in the derivative of the wavelength sensitivity curve, then, voila, more tonal contrast. I suppose this is because small changes in the tone/colour across the subject give rise to large changes in actual density in the neg. Requires more thought.

    I seem to have more success generating tonal interest and good separation with traditional-grained films, and the tones clump up for me with tmax and the deltas. Maybe it's just me :s
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  8. #8

    Join Date
    Jan 2008
    Location
    Sarasota, FL
    Shooter
    35mm
    Posts
    921

    That's exactly what I was after

    Quote Originally Posted by Photo Engineer View Post

    Nothing substantive can be derived from the data you refer to other than the exact sensitivity of the given film itself.

    PE
    The details of how it is done, while I admire the alchemy, aren't important. But I do enjoy hearing your thoughts, always.

  9. #9
    df cardwell's Avatar
    Join Date
    Jul 2005
    Location
    Dearborn,Michigan & Cape Breton Island
    Shooter
    Multi Format
    Posts
    3,342
    Images
    8
    Paul

    Awesome. I'm grateful for folks who see more clearly than I,
    and write more coherently !

    (Many of whom see to be posted ahead of me !)

    Here is a visual aid borrowed from York Univ.


    And below, here is the late lamented APX 100 data.
    Attached Thumbnails Attached Thumbnails agfa apx 100.jpg  

  10. #10

    Join Date
    Jan 2008
    Location
    Sarasota, FL
    Shooter
    35mm
    Posts
    921
    Quote Originally Posted by df cardwell View Post
    Paul

    Awesome. I'm grateful for folks who see more clearly than I,
    and write more coherently !

    (Many of whom see to be posted ahead of me !)

    Here is a visual aid borrowed from York Univ.


    And below, here is the late lamented APX 100 data.
    Thanks for the color graph. There is also one in the UV filter link I supplied, although he has the colors reversed from convention.

    Wow, that APX is quite the roller coaster, even more than Kodak's general curve.

Page 1 of 4 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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