Overexposing C-41 for more saturation rule

Discussion in 'Color: Film, Paper, and Chemistry' started by Athiril, May 24, 2010.

  1. Athiril

    Athiril Subscriber

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    Can someome please post comparison examples of this to actually 'prove' it?


    From my own past results, and seeing those of a user test on Ektar in the Ektar thread show that underexpose gives more contrast and more saturation or perceived saturation.

    While overexposing flattens out the contrasts and the colours seem more muted.
     
  2. L Gebhardt

    L Gebhardt Subscriber

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    I have never noticed that I get more saturation when slightly over exposing C41 film. In fact it tends to reduce contrast in the shadows, and that seems to give less saturation in the shadows.
     
  3. ZorkiKat

    ZorkiKat Member

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    It's like this.

    You really get more exposure in the shadows, and the impression that this will dilute them is right. But with optical printing, a (slightly) denser negative will require longer printing. Longer printing means more exposure in the shadows, and this puts them back in track.

    Scanners behave differently. Usually, the software used to process the image will account both highlights and shadows before a positive picture is produced.

    A dense negative will require lengthier printing, optically. Lengthy exposures causes more halide to be affected. When more halide is developed, more dye is produced. Lengthy printing with a normally exposed negative (with less density) will cause the hues to go dark. But when the dyes in the negative are already dense to begin with- something achieved with overexposure in colour negative stocks- the light blocking power of the dyes prevent details from darkening. The dyes aren't quite opaque enough to totally curtail exposure.

    In the past when we used low grade or "budget" colour negatives (we had low end Kodak colour film which was very pastel, or the earlier Luckycolor films), the only way to give punch to their normally washed out rendering was to slightly overexpose them. The Kodak had a box speed of 100, but it gave nice results at EI 64. Luckycolor and Eracolor (both from China, and this was in the early 1990s) were supposed to be 100, but EI 50 or even EI32 did better. In fact, the "budget" Kodak 100 was eventually repackaged as KodakSP 64.

    These poor grade negative stocks produced low dye densities with normal exposure. The only practical way to make them produce more dyes for more punchy hues was to increase exposure- more exposure, more development, equals more dyes.
     
  4. htimsdj

    htimsdj Advertiser Advertiser

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  5. markbarendt

    markbarendt Subscriber

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    There may be somebody that has examples but (!) the comparison is always tainted by the choices made by the person responsible for printing them.

    IMO, to get a meaningful comparison, you need to try it yourself in your system.
     
  6. Athiril

    Athiril Subscriber

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    Well in scanning I usually scan my my negs as positive, and set the levels for each channels individually, invert then do any colour correction (if needed at that point, usually not).

    markbarendt: I wont be optically printing for a long time yet, so it would be nice to see the results and conclusions of others.
     
  7. holmburgers

    holmburgers Member

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    It has always seemed counter intuitive to me, especially considering that it's common to *under*expose slide film for more saturation.

    I would like to hear some opinions, but would actually prefer to hear some sort of logical theory that could explain these two suggestions. In the meantime, I'll drink some coffee and work on the whole "logic" thing..... :wink:
     
  8. ZorkiKat

    ZorkiKat Member

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    Here are three examples from negatives which were slightly overexposed, which I believe improved the intensity of hues. Or at least gave the colours from film which would otherwise yield flat colours with normal exposure. These are print scans. The change in saturation or intensity is really hard to show using these alone, without comparison, and many of the tones largely lost.

    This one is from about 10 years ago. Shot on Imation (Ferrania) 100 film. This film, normally exposed, gives a pastel palette:

    [​IMG]

    The following are from last year. Shot on Luckycolor 200 film, which again, isn't known for punchy colours. The film was exposed at EI 100 instead.

    [​IMG]

    [​IMG]

    Articles and reviews about colour film negatives published in 1990s photo/trade magazines will likely mention something about the slight overexposure = colour punch routines. Check the American "Popular Photography" or "Modern Photography" (defunct by the early 1990s) features on colour films from this era.

    Most amateur colour film negatives also have official ISO ratings which are lower than their real speeds. Many ISO 100 colour negative emulsions often had real EIs of 160 or even 200. That assured some overexposure- giving both the extra colour punch and an exposure "safety" factor.
     
  9. ZorkiKat

    ZorkiKat Member

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    I hope this kicks in the logic thing...

    Colour slides are processed by reversal. So when chrome film is underexposed, less halide is developed during the first BW development stage, and leaves more undeveloped halide in the emulsion for the colour development after reversal.

    When more halide is left for reversal, more gets to develop. And when more silver develops, the coupling process produces more dyes. And what happens with more dye? More saturation.

    Colour negatives aren't developed by reversal. So underexposing a colour negative emulsion will not yield the same effect as a film which goes through two development, and two exposure stages as it would in reversal (E6) processing

    Underexposure will expose less halide- when less develops, less dyes form too. With less dyes, no saturated colours. Just muddy ones- grey from the lack of exposure, with little dye forming.

    Overexposing (slightly) a colour negative stock OTOH makes more halide develop-able. More halide developing means more dyes.

    A colour negative with punchy dyes will print with more punch on a positive material, when optically printed, that is.
     
  10. holmburgers

    holmburgers Member

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    Awesome, that makes perfect sense. Thanks!
     
  11. markbarendt

    markbarendt Subscriber

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    The results you get are directly related to the processes and equipment you use, the lab you use, etcetera. Change any variable and you get a different result.

    "Normal" in an enlarger is different than in a scanner and different scanners and software packages do different things too.

    Since you are looking for info on how film works when scanned, and your scanning it yourself, I'd suggest that it might be more productive for you to try a forum that supports that digital path.
     
  12. Athiril

    Athiril Subscriber

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    A) The software 'package' is totally irrelevant with the way I scan and correct, even the hardware (apart from monitor) is completely abstract with the way I scan (apart from the digitisation quality), so unless you want to get into a 'digital discussion' please do not try to argue that point.

    B) I'm not looking for info on how film works when scanned, please refer to the thread title.

    C) This thread isn't about scanning, might I suggest you pay a little more attention please? My method isn't the subject of this discussion.


    Your results definately have a certain punch to them.

    I would assume to have a better saturation, that there would need to be better colour separation, but if one colour is already intense bright, will increasing exposure not raise the density of the other 2 colours but not increase the density of the already intense colour much since highlights are restrained more?




    I think a warning should go along with the advice of overexposing C-41 that the increased saturation will only appear in optical prints, I'll have to test if it's equivalent of shifting the black and gamma/midtone points, though perhaps I shouldn't say that here :tongue:
     
    Last edited by a moderator: May 26, 2010
  13. markbarendt

    markbarendt Subscriber

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    Athiril, lets work the basics a bit.

    Overexposure of color negative film moves the placement of each subject in the composition further up the films characteristic curve, the negative gets thicker, harder to push light through.

    So, lets say that you can print a normally exposed negative (in an enlarger) correctly with a 15 second exposure.

    If you print an overexposed negative of the same exact scene with the same 15 second exposure you will get an underexposed print, i.e. reds will move toward white, i.e pink. The negative is simply blocking more light.

    Standard printing doesn't work.

    To fix that issue with an enlarger you add more exposure time to the paper. More exposure on the paper means darker colors. Pinks move back to red.

    There is more to this story though.

    The three color layers in the film don't normally expose evenly, red may be underexposed in the shadows at a normal exposure setting.

    Adding exposure in camera can get all "three" exposures up off the toe and onto the straight line portion of the curve. Once you get all three layers well exposed you can balance the colors better.

    This can, but doesn't always, result in colors you might like better once corrected and placed at the planned brightness on paper.

    It's an art, not a rule.
     
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  15. Athiril

    Athiril Subscriber

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    Well I understand that.

    So printing longer to place the shadows @ shadows on the print so to speak, and will make the highlights (and midtones) on the print denser, and hence more colourful in some cases?
     
  16. markbarendt

    markbarendt Subscriber

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    A denser version of the same color is just darker, that can be achieved with a normally exposed negative by just adding more enlarger exposure to the paper.

    An overexposed negative changes the palette, contrast, and "qualities" of the colors captured.

    The choices of the person processing make all the difference in the world, change the filter pack some and you have a new version.
     
  17. Mick Fagan

    Mick Fagan Subscriber

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    Interesting thread.

    My experience with over exposing colour negative film is that you end up with ever so slightly finer grain.

    One way to test this is to use Ilford’s C41 B&W film and expose a set of frames from gross under exposure to gross over exposure. The grain difference between the two extremes is interesting.

    With an over exposure of around 1/3 of a stop from a film’s true speed, I have generally found colour negative material to give optimum grain, optimum perceived colour accuracy and optimum colour saturation.

    When I wish for good punchy colour, apart from correct exposure and developing of the actual film, I find I need a reduced highlight to shadow range.

    Under controlled studio conditions, super snappy colour prints will emanate from a negative exposed under a lighting situation where one has an approximate range of 4 stops from the shadow reading, to the highlight reading.

    Negatives exposed under this regime are so stupidly easy to print, look so unbelievably good, you start to wonder what the fuss is all about when printing colour in the darkroom.

    One thing with colour negative printing, is the 6 colours. Three of those colours are in the film, two of the colours are in the enlarger, the sixth colour is controlled by exposure.

    Basically you control Yellow (blue in the film) and Magenta (green in the film) using the dials on your enlarger head, or filter packs.

    The Cyan (red in the film) in the enlarger, is not used. Correct red is achieved by exposure (density).

    If you have a print that is quite close to being correct, or is correct colour wise, then making a darker print will add red to the picture. By reducing exposure from correct, you will make the print more Cyan.

    This is effectively how the colour negative darkroom worker, achieves correct colour balance.

    Making a print darker than correct will not make colours more anything, except slightly darker and the whole print will start to get a slight reddish look.

    That said, correct colour is always subjective, but colour negative to positive paper printing, correct or otherwise, is obtained by the combination of the two filters and exposure.

    I have found over the years that the lighting conditions play the most important part of just how punchy (or not) a colour negative print portrays colour.

    So to answer the original question; to the best of my knowledge and experience from printing colour negatives in a darkroom, over exposing colour C41 material does not change the colour saturation component I see in a colour print from one of those negatives.

    Mick.
     
  18. markbarendt

    markbarendt Subscriber

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    I have to agree.

    I lucked into a Color by Bessler "Subtractive Color Calculator" in a box of darkroom stuff that I got at a thrift store. That alone was worth the price of the whole box of stuff.

    Most of the time now one "calculator print" gets me color and exposure settings that are so close it's silly.

    It takes me a lot more work to get a B&W close.
     
  19. hrst

    hrst Member

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    Oh dear, you are way off in almost everything...

    Of course if you expose the paper for longer time, it will get darker, but hey, that is if you have a normal negative! If you have a darker negative, the total light reaching paper when using longer printing time, is the same, given that there is no reciprocity failure. How can you go this off in this kind of very basic principle?

    THEN, more dyes mean "darker" image, it is NOT more saturation. If you have an equivalent amount of cyan, magenta and yellow dye, what you have is grey, and if you increase dye density, you have a darker shade of grey. If you then adjust for this by exposing the paper longer, you are where you started.

    Dyes ARE the image, they are not some kind of colorants for BW image, which seems to be the basis for thinking in this thread.

    The saturation thing has to be explained by different arguments. What I can see here is just misconceptions and new theory around the very basics that are just misunderstood completely.

    I would start searching the answer from the shape of the characteristic curve. It would be quite intuitive that contrast - and perceived saturation - would go low when overexposed because of the shoulder area, but the shoulder is quite far up in the modern color negative films and with usual, low-contrast scenes you are not on the shoulder at +1 or even +2 stops. BUT, on the other hand, by overexposing, you move the shadows, which probably are at toe region, to the linear region that has more contrast. This is simple and understandable, but there probably is something more to this that could explain the phenomenon even better. But it is not the fact that you have to expose the paper "longer". The time doesn't matter (unless reciprocity failure kicks in).
     
  20. markbarendt

    markbarendt Subscriber

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    I agree.

    A given density on the film will create a given brightness level with a given amount of paper exposure.

    What can change by adding film/camera exposure is the color balance, i.e. getting the reds in the shadows up off the toe of the film's curve.

    What has been called more saturation here might be better described as better color balance and placement of tones.

    For the shot of the lady in the red dress in the jungle above, overexposing the film some would really help in getting all the color info onto the film.

    Conversely, in a highly controlled situation like Mick's studio where the color balance starts near to perfect, there little or nothing to gain from overexposure.
     
  21. df cardwell

    df cardwell Subscriber

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    3 reasons to give color negatives generous exposure

    Reason 1

    Color is like B&W in one basic respect --- sufficient exposure of the PAPER is necessary to make a full and strong BLACK.

    Remove the negative from the process for a moment. If you give the PAPER the minimum exposure necessary to make black, you get black. If you don't, you get mucky almost but not quite black. And in color, it is thoroughly disgusting. Obvious, right ?

    Automated color printing machines usually are (were) set up to print the film base to the minimum exposure necessary to make an almost, almost, almost pure paper black. I guess this was the most effective way to make acceptable prints for the greatest number of customers. If you ran the printer in a pro lab, you simply calibrated the system to a real black. This meant than Aunt Milly's pictures were always going to be lousy, but that was OK. Aunt Milly was the customer who dyed her little white poodle green on St Patrick's Day back in 1992 and brought the whole lab to its knees trying to balance out the green from an obviously white dog. You never forgot Aunt Milly, did you ?

    The easiest way to make the automated printer make pure black was to force it to expose longer. Since you couldn't sneak into the lab at night and recalibrate the system to expose for a higher density black you were left with the obvious workaround: make your negatives denser by adding half a stop exposure. The printer was compelled to expose longer, and with a normal subject, you got a real black.

    And a real BLACK is necessary for adequate color saturation IN AN OPTICAL PRINTER.

    Reason 2

    In order to correctly balance the color on color paper, you need to give sufficient exposure. Get the exposure correct, the color falls in line. Over exposed color negatives ( a stop or two) were easy to color balance. Underexposure, impossible. To prevent lousy color, the easy fix was to add a margin of error to your exposure. Shoot 160 at 100, and you were protected from bad color.

    Reason 3

    If you were shooting a JOB.... for MONEY ... with CLIENTS and CONTRACTS.... you added a little extra exposure to reduce the chance of making a stupid mistake and suffering for it.

    There you are, the 3 reasons folks traditionally exposed an extra half stop above the box speed of color negative film.

    But that was a long time ago. Printers which scan film can scavenge more information from underexposure than an optical printer could, and the software can correct the image to print well. There are fewer reasons today than there were 40 years ago to give extra exposure. Saturation can be dialed in by Photoshop if you are not using a closed loop system like a Frontier.

    The need to protect yourself from total failure still remains, and giving an extra half exposure is good insurance... even if you are very careful with your technique.
     
  22. hrst

    hrst Member

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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?
     
  23. ZorkiKat

    ZorkiKat Member

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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 a moderator: May 27, 2010
  24. Photo Engineer

    Photo Engineer Subscriber

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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
     
  25. tiberiustibz

    tiberiustibz Member

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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.
     
  26. df cardwell

    df cardwell Subscriber

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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."