Help ! Dynamic range C41

Discussion in 'Color: Film, Paper, and Chemistry' started by rfshootist, May 31, 2006.

  1. rfshootist

    rfshootist Member

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    Hi to all,

    i have decided to work a bit more careful in future and make a contrast analysis when the lightning (= contrast) gets critical l My Gossen Starlight allows me to use the Spotmeter for that purpose, it calculates the range in fstops.

    I seem to be too dumb to find a reliable source anywhere in the web which tells me something about the dynamic range of C41 film and slide film.

    I have in mind 12 stops for B&W, 6 to 7 for slide, and about ten stops for C 41 (1:1000 ?) , not sure tho if these numbers are up to date for the modern multi layer films, I blieve to remember that somebody said 12 stops for some colour films would be state of the art now ?

    Nice would be also a table, which translates the contrast ratio to fstops ?

    Many thanks in advance !

    Bertram
     
  2. Helen B

    Helen B Member

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    Hi Bertram,

    If you look on page 2 of this thread I have attempted, in my usual convoluted and obscure manner, to cover some of the questions you are asking.

    Colour negative film is more of a part of a fixed system than B&W negative film is. The manufacturer's characteristic curves will tell you the overall dynamic range of colour negative film (with no allowance for contrast reduction by lens flare), but how much of that dynamic range can be used in a single straight print depends on the printing paper. Your film might have a dynamic range of 12 stops, but the characteristic curve of the printing paper results in only seven stops, for example, appearing on a straight print. The rest of the dynamic range of the film could be considered as under- or overexposure latitude. It's advisable to avoid the use of the underexposure latitude, because most colour negative films have a marked increase in graininess at the toe. This is an issue when finding your practical film speed. There is a lot of overexposure latitude.

    If there was a paper made that could use almost the full dynamic range of colour neg film, the prints would look awfully flat for most subjects. You can, of course, make contrast masks and use other contrast reducing techniques to utilise the full dynamic range of the film.

    It's a slightly different matter if you scan (wash my mouth out with soap and water). Then you can capture everything that is on the negative, and adjust the contrast as you wish.

    If the contrast ratio is CR and the stop range is SR stops:

    CR = 2^SR

    SR = log CR/log 2

    Contrast ratio - stops

    32 - 5
    64 - 6
    128 - 7
    256 - 8
    512 - 9
    1024 - 10
    2048 - 11
    4096 - 12


    Best,
    Helen
     
  3. rfshootist

    rfshootist Member

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    Dear Helen

    thanks so much for takin that much time for these detailed and knowledgeable explanations ! You answered all my questions and even some I was too dumb to ask at all !! :smile:

    I knew this limitation of paper but you first made clear to me what that really means for the photog thinking about how a photo must get exposed.
    I mean how to use the film range exceeding the paper range as "latitude"!
    I never had dealt with printing colour, leaving aside some friends experiments with Cibachrome in the 70s, which I observed with astonishment and admiration. All forgotten.

    Thanks for the contrast table too, that was what I needed !
    The limited dynamic range of film, compared to the photogs eyes, is for me one of the most interesting issues in photography, much more interesting than the the resolution issue. Interesting your remark that a paper with the full range would make the prints all look awfully flat in most cases, tho logic I did nor realize it.

    Now let me strain your benevolent patience with a heretical question , I will wash my mouth later too, but with a decent single malt: :D

    Would be an ink jet be able to bring the 10 to 12 stops in the scan file on a paper, thus exceeding a light source based system with traditional light sensitive paper ? And if so ( no reason for me to deal with the art of ink splashing tho) would we then have the flattening effect you have described ?

    Best regards,
    :smile:
    bertram
     
  4. OldBikerPete

    OldBikerPete Member

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    I have printed color negs traditionally and to HP 4-color inkjets after scanning. In my experience, the ability of the inkjet to render contrast is less than chemical processing. In a comparison of 'best practice' photographic print compared with a 'best practice' inkjet print off the same negative - using all of the contrast range available, the photographic print produces a 'snappier' product.
    The ability to attractively render highlights and deep shadow is also reduced with the inkjet print.
    As a result of these the inkjet is not able to render a contrasty negative as well as photosensitive paper.
    If the contrast on the negative is beyond the ability of the photo paper to handle, there are techniques available to allow rendering of most subjects effectively. These are extremely exacting and time-consuming. The Photoshop equivalents performed on a scanned negative are much faster and probably higher quality, producing an acceptable inkjet print which is probably better than most attempts using photo paper.
    Digital printing onto photo paper is different again and something I have yet to try.
     
  5. Bruce Watson

    Bruce Watson Member

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    Most modern color negative emulsions (that would be the Kodak and Fuji lines) have about the same dynamic range as B&W negative films. That is, they can record just about any real-world subject brightness range (SBR) without color shifting or shouldering.

    The largest I've done was with 160PortraVC. According to my Pentax digital spot meter, I went Zone III to Zone XI with detail, so about 11+ stops (the scene was a white flower in direct sunlight in the middle of the day in the middle of June in the Northern Hemisphere). The film did it's job perfectly. I'm guessing it could handle 12 stops with ease.

    As Helen rightly points out, this would be a tough negative to print in the darkroom. So... I didn't. I drum scanned it and printed it with an inkjet (I know, blasphemy!). The reason for this abominable behavior is that scanning takes this huge density range on the film and makes a perfect fit to the ink range on the paper.

    Don't look at me like that. This is the same thing that we do with the Zone System (more or less). In the Zone System we use the film as an intermediary between the SBR and the dynamic range of the paper. In the case above, we would use severe contraction development (N-4 or so) to haul down the density to make the negative easy to print.

    Same thing - different method.

    Anyway, to answer the question asked, really contrasty slide films like Velvia have a lower dynamic range - say 5 stops. Less contrasty slide films have a higher dynamic range, say 6 stops. Modern negative films, both B&W and color, have essentially unlimited dynamic range, say 12 stops. All of this is in my humble experience and is in no way arrived at scientifically and is not meant to be authoritative. And all that.
     
  6. rfshootist

    rfshootist Member

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    This is interesting to read because it is 100% congruent with an information I got from a friend today who does inkjet printing and traditional printing too.
    He says that especially the pigment based inks would close earlier then photo paper tho the file offers about 10 stops from a good consumer scanner with 4,2D = 1:1000 density.
    The whole thing is an academic discussion only for me anyway, just a peripherical consideration for the main issue which made me posting her. I've given up the idea to print my own colour photos with an inkjet, since quite a while, the more I learned of inkjets the more I saw that this isn't what I would like to deal with now , for a lot of reasons.

    Regards and thanks for the input !

    bertram
     
  7. Helen B

    Helen B Member

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    Though it isn't something that belongs here: there is a very wide range of qualities of inkjet print. It is possible to have a noticeably greater density range with a colour inkjet than with a chromogenic print. The way in which shadows and highlights are rendered in an inkjet print is not an inherent property of the ink/paper combination, it is controlled by a combination of things like the input file, the ink settings and the printer profile. The wide density range is there, how it is used it is up to the person printing.

    Best,
    Helen
     
  8. Claire Senft

    Claire Senft Member

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    Kodaks professional photo books indicates that color print paper well is suited for a log densuty range of 1.00 without considering the extremes. C41 films have a gamma of nearly .6..it varies by film. Therefore, ignoring the extremes, a range of densities provided by the subject of 1.66 could be covered (1.0/.6). The number of stops is 5.5 (1.6/.3)... .3 is the commonly used log of 2..2 being the difference made by a stop.

    You can get a wider density range on the negative but this is what a straight forward well made print can handle.
     
  9. Chan Tran

    Chan Tran Member

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    Claire! While the gamma of C41 film is around .6 the gamma of color printing paper is around 1.8 to 2.0. So you still ended up of only a range of only about 3.3 stops. So with the compression/expansion you don't get more dynamic range but rather a lot of latitude.
     
  10. Claire Senft

    Claire Senft Member

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    Are you indicating that RA 4 paper will be incapable of providing a density range of 1.00?

    Are you indicating that with straightforward methods that RA 4 paper when
    exposed from a color negative negative that received normal processing and and was given an appropriate exposure to a scene containing 5.5 stops will not be able to print it satisfactory manner?
     
  11. rfshootist

    rfshootist Member

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    Dear Helen,
    tho the original question was concerning film the thread slipped a bit towards OT, my fault. But the limitations of the printing process made me curious. I think we now are getting to the point where we better should move to the gray area before we get trouble here ;-)

    Your last info is contradictionary to what my friend told me, but, as you said, you can't do it with every printer or ink system and the tuning of the software is a decisive point too, especially if it comes to B&W. Means tho best case you get all these 10 stops on the paper which the 4.2D of an average consumer scanner is able for. AFAIK my friend works with a not too sophisticated ink system, could be therefore his achievable dynamic range is limited.

    I should add tho that some stops more would not be reason enuff for me to buy an inkjet, there is a bunch of good reasons to stick with the traditional process anyway. I think we all know these reasons good enuff, not necessary to explain anything here.

    Best regards,
    bertram
     
  12. rfshootist

    rfshootist Member

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    correlation of ISO and dynamic range ?

    Yes and it made me forget another ( maybe dumb) question I wanted to ask too: Is there a correlation between ISO and dynamic range ? Like higher ISO= reduced range ? I would deny it becuase I cannot see any technical causality. Do I miss anything ?

    Time to learn more about that all, I always just press the release button and let me surprise...........

    bertram
     
  13. Photo Engineer

    Photo Engineer Subscriber

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    The range of tones in a reflection print are limited by the physics and optics of reflection print materials. This means that the image is limited to a range of densities between about 2.2 and 0.1. To look good, the final image should have a contrast of about 1.5, and from this you can figure out what the range is in stops of exposure.

    The range of tones in a slide are similarly limited to a range of about 3.5 and 0.2. This is with an average contrast of about 1.7.

    A reflection print actually has a much higher tonal range than we commonly see, nearly matching a slide, but to reveal it, one must overcome the physics of surface reflection and illuminate the print with a very very strong spotlight. In that case, you can see above the 2.2 limit imposed by diffuse illumination and view the extended range that is blocked by the multiple surface reflections absent in a transparency.

    Generally, the tonal range is not influenced by a films ISO speed, however, some films suffer from limited tonal range through design or through faults. The tonal range of a neg-pos system is more a function of both the film and paper. Negative films when printed and reversal films, when printed or projected, will generally exhibit similar overall tonal ranges everything else being equal, but the negative film will always have the edge in latitude while any projected image will display a longer tonal range due to the extended dmax available. Negative films will also always display more accurate color, while reversal films will display more exaggerated color due to contrast and inherent chemistry.

    PE
     
  14. rfshootist

    rfshootist Member

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    Fascinating, I never thought about this possibility to make more details visible on a print. And thanks for confirming my assumption concerning ISO and dynamic range.
    As always the whole technical discussion gets really intersting first when the numbers are put in relation to the limits of the human perception. And then it also turns out first who the real experts are who have gained their knowledge in practical work and who are those who live on hearsay.
    I had similar experiences in that never ending resolution and sharpness discussion.
    Thanks to all the friendly people who have posted here, for taking the time. I have learned some new lessons !

    Bertram