Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,042   Posts: 1,560,726   Online: 1089
      
Page 6 of 8 FirstFirst 12345678 LastLast
Results 51 to 60 of 80
  1. #51
    Saganich's Avatar
    Join Date
    Nov 2004
    Location
    Brooklyn
    Shooter
    35mm
    Posts
    447
    Images
    176
    I use my transmission/reflection densitometer to determine the density range for a particular film developement process. In large format I make a Zone I exposure and a Zone VIII exposure. Develope both negatives exactly the same and measure the density. I target the density range for the type of developement process I plan to undertake. For normal cold light enlargement I find a range of 1.25 between these zones good for grade 2 or 3 paper. The VC paper seems to need a bit less contrast.

    I target zone I density around 0.10. If the density is too low, say 0.05, then the film may need more exposure so drop the ASA one stop say from 400 to 200 and make two more exposures. This will shift the entire range to the left. The Zone VIII density is controlled via time and agitation, more equals higher density range. The confusing part is that extending time also bumps up Zone I density. This is particulary true for Metol developers. I found that this should be a compulsive issue but is well worth the effort. The next step after this is to look at the relationship between green and red filteration and density. I recently discovered a rather pleasing effect when pushing film and using red filters for sunny landscapes.

    It is usefull to have a reflection and transmission standard to make sure your equipement is operating correctly. Stouffer makes many usefull densitometer accessories. http://www.stouffer.net/TransPage.htm
    Chris Saganich
    http://www.imagebrooklyn.com

  2. #52

    Join Date
    Apr 2005
    Shooter
    35mm RF
    Posts
    295
    Quote Originally Posted by Saganich
    I use my transmission/reflection densitometer to determine the density range for a particular film developement process. In large format I make a Zone I exposure and a Zone VIII exposure. Develope both negatives exactly the same and measure the density. I target the density range for the type of developement process I plan to undertake. For normal cold light enlargement I find a range of 1.25 between these zones good for grade 2 or 3 paper. The VC paper seems to need a bit less contrast.

    I target zone I density around 0.10. If the density is too low, say 0.05, then the film may need more exposure so drop the ASA one stop say from 400 to 200 and make two more exposures. This will shift the entire range to the left. The Zone VIII density is controlled via time and agitation, more equals higher density range. The confusing part is that extending time also bumps up Zone I density. This is particulary true for Metol developers. I found that this should be a compulsive issue but is well worth the effort. The next step after this is to look at the relationship between green and red filteration and density. I recently discovered a rather pleasing effect when pushing film and using red filters for sunny landscapes.

    It is usefull to have a reflection and transmission standard to make sure your equipement is operating correctly. Stouffer makes many usefull densitometer accessories. http://www.stouffer.net/TransPage.htm

    This is a way of measuring contrast, but it is not CI. CI has nothing to do with zones, which are measures of print density, not negative density. CI is an invention of the Eastman Kodak Company and has nothing to do with the ZS.

  3. #53

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Quote Originally Posted by Stephen Benskin
    Sandy's reprimand of OP's use of proper technical terms can be applied to himself. SBR is an out of date and inappropriate term. Brightness is a subjective term and has not been used since the 1950s or 60s. The correct term is Luminance Range which is psychophysical. The abbreviation is generally LSLR. You can also us log-H Range when referring to the characteristic curve.
    SBR is a term used by Phil Davis in Beyond the Zone System and is at the core of the BTZS system of exposure and development. It describes the difference in luminance range as determined by two incident readings, one taken in the shadows and another the highlights. The difference is then addded to 5 to give the SBR of any specific scene. SBR is then used to determine time of development. Davis uses the term SBR instead of SLR because of possible confusion of the later with widely used term single lens reflex. There is absolutely nothing psychophysical about SBR, though one can fudge it up or down for interpretative possibilities. You may find the term SBR inappropriate but as described by Davis in BTZS it is far from subjective.

    Sandy King

  4. #54

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Quote Originally Posted by Stephen Benskin
    First of all Michael /OP isn't totally wrong on his concept of blank film and CI. He is just being extreme in the example.
    OK, if he is not totally wrong explain in what way he is right?

    Sandy King

  5. #55
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,218
    Let's not get all defense now. Perhaps subjective isn't the best term. It is subjective in that SBR is a psychological term. If you or Davis ever uses logs to define SBR, then it is entirely inappropriate usage. LSLR is a psychophysical term and is a more accurate term. I don't care what Davis says. My point is that let thee not judge for thee may be judged.

    How can OP not be totally wrong on the blank film? What if you process a film to a CI .56 and the LSLR is only 1.9 with a flare of .30? It's not going to give you the same density range as if the scene had a 2.2 LSLR and 0.30 flare. Still, it is processed to a given CI. Same concept if the film is blank. Not that I'm saying OP had a good example there, but he didn't have to beaten up over it. And yes Sandy, I find some of your explanations less than perfect too, but perhaps I'm just more polite about it.

    I've made an attachment comparing CI, Ilford's Average Gradient, and the Zone System.
    Attached Thumbnails Attached Thumbnails Graph 2.jpg  

  6. #56

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Stephen Benskin wrote:

    “If you or Davis ever uses logs to define SBR, then it is entirely inappropriate usage. LSLR is a psychophysical term and is a more accurate term. I don't care what Davis says.”

    I have the definite impression that you are not familiar with Davis’ use of the term SBR. That being the case there appears little reason to continue to discuss the matter. In any event I am using the term as Davis explains it and not within any other context.

    The example you give to explain why OP is not totally wrong on the blank film is based on what I consider improper use of the term “process film to a given CI”. Blank film can not be developed to any CI other than 0.00 because CI is not a process but an end result that describes an average slope. For there to be any slope at all is dependent on two conditions, exposure and development. Your use of the term “process to a CI of n” implies that you see it as a process amounting to a given period of time for a particular film and devleoper. This makes sense in most situations because exposure is presumed. But a film that has received no exposure can not be developed to a CI of anything other than 0.00 because it can never, for all practical purposes, have any slope.

    Sandy

  7. #57
    smieglitz's Avatar
    Join Date
    Oct 2002
    Location
    Kalamazoo, Michigan, USA
    Shooter
    Large Format
    Posts
    1,864
    Images
    97
    Quote Originally Posted by Stephen Benskin
    ...
    How can OP not be totally wrong on the blank film?...
    Stephen,

    I fail to understand your argument here. If the film is blank it has no exposure and it doesn't matter what you call the exposure term on the graph. That exposure value is zero and the film will be at the fbf level no matter how much development you give it or what CI your development would produce on an exposed film. On an unexposed film you won't have flare. Without an exposure difference/contrast there will be no development contrast. There will be no luminance range or subject brightness range and regardless of which arc or system one uses the value will be zero. There will be no contrast by definition. How can you defend any other position in that example?

    Unless you can address that specific example I'll have to assume you are simply trying to bait us as OP has. Both you and OP have sidestepped on the point of unexposed film and contrast. I think you'll find others and myself participating here to be quite rational and not interested in carrying on an extended dialogue with those only seeking to get an emotional response from us. That just ain't gonna happen. If his intent is only to inflame, OP will just have to find another sandbox, or litterbox as the case may be.

    OTOH, we welcome intelligent and altruistic discourse and enlightening conversation. Several of us have tried to be helpful and genuinely assist the thread originator with his question. Others have thrown up a pseudo-intellectual smokescreen which is counterproductive to the interests of all participants.

    Joe

  8. #58

    Join Date
    Apr 2005
    Shooter
    35mm RF
    Posts
    295
    Quote Originally Posted by smieglitz
    Stephen,

    I fail to understand your argument here. If the film is blank it has no exposure and it doesn't matter what you call the exposure term on the graph. That exposure value is zero and the film will be at the fbf level no matter how much development you give it or what CI your development would produce on an exposed film. On an unexposed film you won't have flare. Without an exposure difference/contrast there will be no development contrast. There will be no luminance range or subject brightness range and regardless of which arc or system one uses the value will be zero. There will be no contrast by definition. How can you defend any other position in that example?

    Unless you can address that specific example I'll have to assume you are simply trying to bait us as OP has. Both you and OP have sidestepped on the point of unexposed film and contrast. I think you'll find others and myself participating here to be quite rational and not interested in carrying on an extended dialogue with those only seeking to get an emotional response from us. That just ain't gonna happen. If his intent is only to inflame, OP will just have to find another sandbox, or litterbox as the case may be.

    OTOH, we welcome intelligent and altruistic discourse and enlightening conversation. Several of us have tried to be helpful and genuinely assist the thread originator with his question. Others have thrown up a pseudo-intellectual smokescreen which is counterproductive to the interests of all participants.

    Joe

    You're right that measured CI requires both (calibrated) exposure and development. But once the development conditions have been identified, that can serve as a reference. In this extended sense, then, CI can mean 'amount of development' without reference to exposure.

    In other words, if developing a TMX control strip in D-76 1:1 for 10 minutes at 68F produces a measured CI of 0.56 (using your tank and agitation method) then for all practical purposes all other TMX developed in the same way will be developed to/for (I'm not sure there is a distinction) a CI of 0.56, within the normal tolerances of development. It has become a reference at that point. You don't need to measure every time, unless you suspect some problem with the products or water. Labs run control strips regularly so they know how their film is being developed. Without a control strip, it is almost impossible to measure CI. Fortunately, you really don't need to. If normal scenes look right on normal paper (grade 2-3), you're doing fine.

  9. #59

    Join Date
    Jul 2003
    Location
    Texas
    Shooter
    Multi Format
    Posts
    3,576
    Images
    27
    Quote Originally Posted by smieglitz
    Stephen,
    .........
    OTOH, we welcome intelligent and altruistic discourse and enlightening conversation. Several of us have tried to be helpful and genuinely assist the thread originator with his question. Others have thrown up a pseudo-intellectual smokescreen which is counterproductive to the interests of all participants.

    Joe
    Thanks for that comment Joe...
    Mike C

    Rambles

  10. #60

    Join Date
    Apr 2005
    Shooter
    35mm RF
    Posts
    295
    Quote Originally Posted by photomc
    As the new owner of a densitometer, attempting to get a better understanding of how it is used to determine the contrast index (CI) of a negative. Can someone point me to a resource that might help explain how the CI is determined or perhaps offer a little Densitometery for Dummies...

    Thanks,
    1) Unless you process control strips, you cannot measure CI directly

    2) You don't really need to know exactly what your CI is for practical purposes

    3) Why? Because ordinary photography does not require that kind of precision

    Why did you buy the densitometer?

Page 6 of 8 FirstFirst 12345678 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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