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  1. #41

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    Quote Originally Posted by AndreasT View Post
    What does this mean?

    ..... that print quality requires the mid-tone reproduction gradient to exceed the mid-tone contrast of the original scene.
    If you graph original "scene density" vs print density, it seems like you would want them to be the same (ie., a 45 degree line). Such that a photo of a gray scale should be printed so as to be identical to the original. This works great for reproduction of art work.

    But...if you do the same for a real-life scene, the print has a dull, blah sort of look to it. If you make another print, with slightly more mid-tone contrast, it looks lively and "just right." A graph of this reproduction will be steeper in the middle, demonstrating what Steven has said. (I should mention that I've only done this with studio portrait work; I presume it won't matter when the scene is foreign to the viewer.)

    It seems sort of odd that this would be true, yet it seems to be so. I don't fully understand why - it is often explained as due to viewing flare and/or the print not being as bright as the original scene. I'm not fully satisfied with the reasons, but I'm convinced of the results.

  2. #42
    AndreasT's Avatar
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    Ok, so you mean the mid tones are step the lights and shadows are flatter?!? Like the classical s-curve, am I seeing this right.

  3. #43
    Stephen Benskin's Avatar
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    The tone reproduction chapter in The Theory of the Photographic Process 3rd edition covers both objective and subjective tone reproduction in great detail. Along with the mid-tone gradient, one other critical condition is required. The print tones need to be lighter than the original subject.

    Here's an example of a four quadrant reproduction curve. The upper right quadrant is the actual reproduction curve. It compare the original subject with the resulting print.

    Click image for larger version. 

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    And here's one that shows the effects of extended processing to compensate on underexposure has on the reproduction curve.

    Click image for larger version. 

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    Last edited by Stephen Benskin; 03-06-2013 at 08:04 PM. Click to view previous post history.

  4. #44
    AndreasT's Avatar
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    Aha, in example two the mid tone gradient is lower, am I seeing this right?
    Why do the print tones need to be lighter.
    For me the second example looks as if the print density looks right, well it is lying more on the straight line.

  5. #45
    Stephen Benskin's Avatar
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    Page 464 from The Theory of the Photographic Process, "The illuminance of the photograph generally must be greater than that on the original scene if exact luminance reproduction is to be obtained. The reason for this requirement is that the semispecular reflections from shiny objects in the scene, such as hair, eyes, certain areas of the skin, jewelry, certain types of cloth, glassware, ceramics, fur shiny leaves, rippling water, and many metallic objects, usually have a luminance greater than that of a diffuse white object in the scene. If the diffuse white object were to be recorded at the maximum reflectance of the photographic paper (approx 90%), the shiny areas of the scene could not be reproduced at the required higher luminances. For true reproduction, therefore, the diffuse white objects in the scene must be recorded at a reflectance less than 90% so that the shiny areas in other objects can be recorded at 90% and thus have a luminance higher than that of the photographic record of the diffuse white objects. If for example, the diffuse white objects in a living room scene lighted with 100 foot candles are reproduced so that they will have a reflectance of 45% in a photographic print and the brighter, semispecular objects are reproduced at a reflectance of 90%, the illuminance on the photograph must be 200, rather than the 100 foot candles."

    Later in the chapter, page 466, "The gradient in the middletone region was always greater than 1.00 (usually 1.10 - 1.20) for the preferred prints of all the scenes studied. Whenever the middletone gradient was less than 1.10, the prints were unanimously rejected as being "too flat". Whenever the density level of the prints was great enough so that the curves closely approached the 45 degree reference line, the prints were unanimously rejected because they appeared too dark."

  6. #46
    AndreasT's Avatar
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    And the shadows and lights are reproduced softer. Right.
    This made me thing on another line. If the midtones need to be a bit more contrasty.
    Would that call for films with a more pronounced curve, like older films where there is a larger toe and rounded shoulders. The same regarding papers.

  7. #47
    Bill Burk's Avatar
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    Quote Originally Posted by AndreasT View Post
    And the shadows and lights are reproduced softer. Right.
    This made me thing on another line. If the midtones need to be a bit more contrasty.
    Would that call for films with a more pronounced curve, like older films where there is a larger toe and rounded shoulders. The same regarding papers.
    The toe of the film and the s-curve of the paper - they work together to create the "preferred" print reproduction in the fourth quadrant. The paper curve was deliberately shaped to make it all come together in the print.

    Now any decision to use part of the toe, or go the other way and expose on the straight line, may be important to consider the impact this has on how well your results fit that preferred reproduction curve.

  8. #48
    Stephen Benskin's Avatar
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    There's a paragraph on page 489 that speaks to both Michael's question and Marks statement. It refers to a study by Jones and Nelson on the relationship between the negative and the print. "According to the findings, a strong correlation exists between the density range of the negative and the log exposure range of the optimum paper only if the variations in the density range are due to differences in development, level of camera exposure, or type of film. When the negative density range are due to differences in the luminance range for the scenes, the correlation is weak. In fact, when the film characteristic, camera exposure, and negative development are accurately controlled and held at what might be called the "normal" level, there is a distinct tendency for observers to prefer prints made on the "normal" grade of paper (such as Grade 2), regardless of the luminance range of the scene. Although this tendency may seem odd, it appears to be confirmed by the common practice of photofinishing stations, where accurate control of the processing of films having uniform contrast characteristics has been found to allow the use of a constant grade of paper."
    Last edited by Stephen Benskin; 03-06-2013 at 10:07 PM. Click to view previous post history.

  9. #49
    markbarendt's Avatar
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    Stephen I have the 4th edition, page doesn't match. Can you give me a figure number of chapter/section landmark?

    Thanks
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  10. #50
    Stephen Benskin's Avatar
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    Chapter 22, subsection "Objective Tone-Reproduction Analysis." Past Fig 22.18 and equation 22.26.

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