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  1. #21
    hrst's Avatar
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    I agree with all of the above reasons. Reasons 1 and 2 are simply because the toe is lower in contrast. Overexposing a bit will place the image information on the linear region.

    Reason 3 takes also advantage of the very long linear region; it's more safe to overexpose than underexpose, because toe is much more near than shoulder.

    I also agree with the color balance thing. If your light source is exactly at the correct color temperature, then there's little problem, but if the color temperature is off, you have to balance the colors in printing, and it's naturally easier when all the information is on the linear scale; you can just slide the curves. But, if some color (red in the case of cold light in the shadows, or blue in the case of tungsten lightning) lacks exposure and the important parts of image is placed on the toe, you'll get contrast mismatch and muddy/colored shadows or crossover.

    Scanning naturally gives the option to modify curve shape to linearize the toe and shoulder regions by applying an "anti-S" curve.

    But is there something else to the saturation question?

  2. #22
    ZorkiKat's Avatar
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    Years ago Ralph Gibson was said to have overexposed his TriX and developed them vigourously in 1+25 Rodinal to get really dense, high contrast negatives. Not the sort obtained using the textbook methods. The result, those stark black and whites seen in his books like the "Sonambulist". The theoretical reason for being was that the shadows (in the negative) can be exposed longer to draw blacks from the paper without having the light parts degrade into grey.

    Some of this can perhaps be translated to colour negative work. A film known for making less than vibrant dyes in its negative will produce prints with less punch. Dyes which form in the negative are transparent/translucent for the most part. Weak densities let more light in. So a red object represented by weak yellow and cyan dyes in the negative can only expose the paper for so long before tomato red degrades to gore red. However, if some way were done to increase the densities of these dyes so that their combination can make for a denser green, the paper can be exposed longer to get something like apple reds or blood reds without going black immediately. And the way to increase the densities of these dyes is through a bit of overexposure. Unlike in BW developing, it is not possible to increase the dyes densities through extended developing without giving rise to an adverse reaction like erratic dye formation.

    Negatives, be their image be in metallic opaque silver or translucent dye, are intended to block and pass light selectively. How they do this depends on the density of the images they contain.

    "Darker" hues can be taken for saturation in this case. A weak red on the print made from a negative with low dye densities will look pale. Not enough red, with more white from the paper base passing through. A strong red from 'overprinting' can be described as dark- but it still will look more intense than a paler one. Exposing longer to get a stronger albeit darker red is like applying more red paint to get the colour significantly stronger. And what way could be thought of which can cause more magenta and yellow dyes to form in the paper emulsion? Wouldn't slight overexposure (overprinting?) fit the bill?

    I can't say much about the theories. I'm not a stranger to colour printing in the darkroom too. It was the last type of wet work I did before I quit darkroom printing years ago. And making slightly overexposed negatives for extra punchy colour prints had been a very convenient and consistent method for me then.
    When I started scanning colour negatives it became evident that the same didn't work. The ccds on the machines didn't like dense dyes and caused a lot of trouble- low contrast and loss of saturation among them.

    Df Cardwell mentioned the "shoot 160 at 100" to protect from bad colour. Technical sheets from colour film manufacturers would indicate that their emulsions were really faster than their box speeds. Fuji Superia 100 had been really EI 160 for ages. The Agfacolor 100 (Agfa's first C41 compatible colour negative film) from the early 1980s was really a 200, but Agfa said something to the effect that the colour rendition improved with this sanctioned overexposure.
    Last edited by ZorkiKat; 05-27-2010 at 08:49 AM. Click to view previous post history.
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  3. #23
    Photo Engineer's Avatar
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    Well, let me blow everything out of the water (to a certain extent)...

    The curve of C41 films is supposed to be linear at a gradient of 0.6 - 0.7 (depending on film and mfgr) until it reaches dmax at which point there is a shoulder.

    Ideally, if you overexpose and stay on the linear part of the curve then the image should be the same from the inception of the toe to the inception of the shoulder, thus giving you the SAME saturation as long as you are on this straight portion of the curve. In the toe and shoulder, due to lower contrast there, you should see less saturation.

    Now, since there is more silver (and different emulsions coming into play) at higher densities, there is a theoretical change in the amount of interimage and correction that can come into play over the upper part of the curve, but the engineers strive to keep this effect as linear as possible, to keep changes at a minimum. This effect, as well as granularity are kept in check by a method called coupler starvation which means that as you get more silver, there is less dye formation per unit silver to PREVENT a change in saturation and an increase in grain.

    Be that as it may, I have not been able to demonstrate a large change in dye saturation when I overexpose a C-41 film. This was done with identical exposures from ISO 25 - ISO 400 with an ISO 160 film and from ISO 25-1600 with an ISO 400 film (Portra VC films, 120 format, Mamiya RZ67, manual adjustment of exposure)

    PE

  4. #24
    tiberiustibz's Avatar
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    That's right. We could test this...

    I'm sure that altering exposure changes contrast. I intend to try this out sometime when I have time to burn.

    BTW, you don't use the cyan dial because your net filter change is towards red, thus cyan is going in the incorrect direction. You can manipulate colors in any direction without using the cyan dial for this reason.

    Today's minilabs are digital and saturation is controlled by a lovely slider bar on the software.
    --Nicholas Andre

  5. #25
    df cardwell's Avatar
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    But is there something else to the saturation question?

    Not really. It was an old wives tale from the '50s and '60s that has taken root in the collective photo wisdom of the internet.
    There really isn't point to do it today, except to reduce the chance of underexposure by error.

    AS Nicholas sez, "Today's minilabs are digital and saturation is controlled by a lovely slider bar on the software."
    "One of the painful things about our time is that those who feel certainty are stupid,
    and those with any imagination and understanding are filled with doubt and indecision"

    -Bertrand Russell

  6. #26

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    I'm sure I can dig up examples if you still need them. I've been shooting Reala 100 @ 50 for about 4 years, but also the Fuji 3 and 4 layer consumer rolls of 200-800, and always gave them + 1/3 to +1 EV bumps.

    A lot depends on if you post process or not. If you do, you can add shadow detail and saturation later, but at a loss of fine details, in some cases.

  7. #27
    Mick Fagan's Avatar
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    The only sure way I know to get more colour saturation and sparkle in a colour print is a method I used quite a few times many years ago. However this is not over exposure of a negative as requested by the OP.

    http://www.apug.org/gallery1/showima...imageuser=7969

    If that link works, it will take you to my gallery, there you will find a half colour and half black and white print.

    The explanation is in the text.

    I think most of you are forgetting the original person and his request.

    He is, as far as I can work out, not using electronic means for obtaining colour saturation. He is not wishing to use electronic means.

    I don't use electronic means, I just fiddle with things and if I wish to know something I'll research as far as I can, then I'll do my own experiments to ascertain if what I have gleaned works for me, or is true.

    PE, very interesting. I remember reading somewhere else on this forum about your experiments regarding over exposure of C41 colour negative material, as you have just re-explained.

    Mick.

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