Portra 160 VC or color negative exposure experts?

Discussion in 'Color: Film, Paper, and Chemistry' started by Juan Valdenebro, Aug 5, 2010.

  1. Juan Valdenebro

    Juan Valdenebro Member

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    Hi from Barcelona, this is my first post here...

    My question is:

    How does exposure affect Portra 160 VC's tone if we talk just about color temperature?

    I'm testing it and found it goes both warm and cold with overexposure depending on the kind of light in the scene, and there's no optimal ISO rating: there are optimal ISO ratings depending on the kind of light... I find the best, cleanest, most accurate colors, are obtained after incident metering at 160, 80 and 40, depending on the nature and direction of light, and looks like the change in color temperature is more than visible with a 1 stop variation...

    Has someone got similar results?

    Cheers,

    Juan
     
  2. markbarendt

    markbarendt Subscriber

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    Welcome,

    With negative film you are getting 3 separate exposures, R,G,B.

    Exposure choice just gets them all on the film at some brightness level, it doesn't change the film's temperature response.

    Color correction/balancing is an expectation/requirement of the process during printing.

    You can also use filters on your camera to change the color balance.
     
  3. Juan Valdenebro

    Juan Valdenebro Member

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    Thanks for the welcome, Mark...

    Indeed I used a B+W 81B filter on my Nikkor 105 2.5 for all the shots in the test, those under direct sun and of course those in the shadows... Have you used that filter? Its tone is a soft, warm delicate yellow, very mid afternoon sun-like, instead of the usual Nikon A2 I use for landscapes for an even warmer look: I prefer the B+W for skin (less amber...) My test was done by noon, so the direct light used was neutral, and not as warm as to consider my filtering excessive... I used that filter to replicate my real shooting...

    I did test two different scenes under direct frontal sun, two under lateral direct sun, and two in the shadows, and each pair showed exactly the same results... If you have a serious test where no tonal change regarding color temperature: cooler or warmer frames can be seen when comparing N, N+1 and N+2 (incident metering) I'd like to see it...

    Thanks a lot!

    Cheers,

    Juan
     
  4. Tim Gray

    Tim Gray Member

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    It is worth noting that if one of the color components starts to shoulder off (or behave in some other nonlinear manner) at a given amount of exposure, then the color balance would shift. I don't know how this applies to Portra 160VC.

    When I look at the Portra characteristic curves, I do see the green curve having a noticeably different slope than the others.
     
  5. Robert Budding

    Robert Budding Member

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  6. hrst

    hrst Member

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    I have to add that if you shoot in too warm or too cold light and want to correct it in printing - and you don't have filters with you when shooting - then overexpose a bit. This way you can stay off the toe for every curve. There is more linear reserve for overexposure. OTOH, if you shoot at correct color temperature, box speed gives you guaranteed results.

    You can overexpose as much as the filter factor for the appropriate filter would be, or maybe a little less. For example, if you overexpose two stops when shooting in 2800K tungsten light, you get the blue curve at the same place you would get with 80A filter (IIRC). Red curve gets overexposed severely without the filter, of course, but it can withstand it much better than two stop underexposure in blue curve.
     
  7. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Tim,

    I agree with you... There is a shift in color balance... Certainly it must be based on slight higher under or overexposure in one layer...

    To be precise about my test:

    My scenes (warming filter on always: just one third of a stop so I metered at 160 always anyway...) under direct sun show underexposure at box speed (160 incident), and a cool (blue-magenta) shift giving sick, dark greens, and slightly unbalanced skins... If the sun is right behind me, +1 is great, with vibrant sunny mood (+2 clearly washed out), and if the sun is lateral, +1 is cold yet, and +2 is perfect: warm and with open shadows and saturated colors.

    But my scenes in the shadows are just the contrary: at box speed (160 incident and filter on) are warm and very nice, and +1 and +2 produce colder results! (+2 more than +1, but +1 clearly cold)... Identical on the two soft light scenes I did!

    This made me remember sometimes there are crossed opinions about exposure and overexposure of color negative film: while the common belief is overexposing a stop, some people say they prefer not doing it because the best colors are found at box speed: all my previous tests for years were done giving the highest importance to direct sun... But now with different light scenes to be sure and also twice to double check results, I can't forget what I see... Direct sun likes overexposure, but soft light doesn't... I can't imagine the technical reasons, but they're here... And I didn't scan home: I'm checking pro lab prints: they scanned after I told them not to correct anything while scanning, and knowing I was looking precisely for color variations produced by different exposure values...

    I'll shoot for some time like this... Of course AE can be very bad here, and even any in camera metering, as a one stop variation from incident is very noticeable... I have years experience in color balance and in selective color in photoshop, and I know that even if we can do things, once the scan is too cold, no matter what we do, it will never look warm and real sunny and happy even if we place the skins just where we want... That's why I'm being picky with this...

    Maybe someone shooting Portra 160 VC can use three frames in the middle of a roll to try this recipe and tell us later if those frames came out great...

    Direct sun, incident+1 with warm filter... Lateral sun, incident+2 with warm filter... Shadows or overcast, plain incident with warm filter...

    Yet I'm curious about the chemical / optical reasons for that "inverse" behavior depending on the kind of light...

    Could it be something about the scanner detecting a much colder image when the scene is a non-direct sun one? If it's that, what really matters is that the scanners work like this, and the direct scan prints are beautiful even before any digital treatment of color...

    Let's wait for some other members opinions and results...

    Cheers,

    Juan
     
  8. Tim Gray

    Tim Gray Member

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    Agreed, they are linear, but I'm seeing different slopes for sure. I fitted to the plot and the blue curve is definitely steeper than the other too. I would think that means that at higher exposures, the blue layer is denser compared to the others than at lower exposures. But maybe I'm reading too much into the chart.

    Also, you linked to the older Portra sheet. The thing I'm talking about is more evident in e-4040.

    Also, Juan, did you have a gray card you are using as a color reference in your shots? I would think that is important for this kind of test...
     
  9. Juan Valdenebro

    Juan Valdenebro Member

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    I didn't include a gray card this time both because I did it shooting unknown people in the street, and because I didn't want to print the gray card neutral (should always appear warm because of my filter, and there would be no way to decide exactly how warm...), so my goal was finding the point of exposure where a given scene looks just like I saw it, and not the usual colder renderings... And indeed I did include some grays and neutral tones (floor, buildings, etc...) and on them it's easy to see the color temperature variations... Every image was (quickly and handheld) done at N, N+1 and N+2, and I did two scenes for direct sun, two for lateral sun and two for shadows, and on each couple the results are gradual on those neutral tones, and identical... And yesterday I checked my Sekonic with all my cameras and everything is spot on...

    Another thing that surprised me, is that finally the best possible amount of light I found for every kind of light scene, curiously was EXACTLY the amount of light I use for B&W... For B&W I use N for soft light, and +1/+2 for direct sun (with shorter development) depending on the angle of light... I don't know if I should think this is strange or logical...

    The skins change, and the neutral tones change in an even more visible way, but the green tones (grass, trees, bushes) are the ones that suffer the most evident underexposure at box speed on direct sun... I'd say the green layer is the most sensitive to underexposure, or the one that requires more light or more precise exposure, or the one with less latitude... One stop before there's a bit of blue present in all greens (totally unreal grass tone), and one stop after the best value, the green and all the rest are weak and washed out (green goes to yellow...)

    I'd like to see someone else shooting with these metering values, and then comment... This is the first time in all my life that I feel I can get the best tone from a color negative scan without any trace of doubt... Just as if I was using slide film... Not just the skin, but the whole mood is "sunny" as we see the real world...

    Cheers,

    Juan
     
  10. markbarendt

    markbarendt Subscriber

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    If I were shooting slides I'd probably use the filter like you suggest, because in that situation you are using the camera to expose the media that will become a finished product.

    With negative film things are different, the negative is only an intermediate step, it requires another exposure and color correction, no if's, and's, or but's.

    A very slight tweak to that color correction will replicate an 81B. (Instructions to a good lab will also get this result without the need for an 81B.)

    There would be temperature changes if you had, for example, underexposed the blue layer in one shot then increased exposure.

    Robert Budding provided a link to the Kodak data on this film, on page 8 at the top corner notice the characteristic curve and that there's no shoulder shown in the graph, essentially they ran out of chart before the film ran out of straight line. The over-exposure latitude of C-41 film is huge.

    This is important because once you get all three colors exposed well (off the toe & onto the straight line portion of the curve) your color balance becomes stable. For normal contrast scenes you would have to over-expose 3+ stops before color casts might start again so exposing for the shadows essentially makes an easy to print negative.

    This is the reason many people overexpose C-41 a bit all the time.

    For large color temp changes an 80 or 85 filter would provide real value, for your example of slightly warming the scene I wouldn't bother; I'd just adjust at the enlarger because I'm already adjusting, there is no extra work.
     
  11. Robert Budding

    Robert Budding Member

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    Are you making optical prints, or are you scanning and inverting? If scanning, it could very well be a problem with your post-processing.
     
  12. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Mark,

    Thanks for your advice, but I do prefer filtering my negative film and getting the best possible colors in my original...

    I scan my slide film too: I don't show the real slides, and in your same way of thinking I could not filter them and just play with photoshop, but with slide film I prefer to filter... It's the same to me: the only difference is that I don't see my negatives in positive, but a better tonality is there after my filtering...

    I know digital processing of color can be more effective if the negatives are not too away -in color temperature- from the real scene...

    I understand you feel fine leaving it all to digital or enlarger filtering... Thanks!

    One more thought: the idea of negative film as a "huge latitude" media comes from the possibilities we have to change it in that intermediate process between the original and the final output, but it doesn't mean that a perfectly exposed negative frame, and another "usable" and under or overexposed one are just the same... No... Slide film, B&W film and color negative film, all have the same or close latitude... It's not true that color negative can be shot with three stops of difference and there's no color change... Those two negative color frames are just as different as what we see if we contact print a B&W negative strip with the base reaching pure black: there's just one exposure that gives us the best tone, no matter if you can "use" another one and help it and filter it with the enlarger or digitally... The differences in color negative are even more problematic than those in B&W: the changes in contrast and in tonal gradations of specific colors rendered as gray on B&W film are less problematic because everything is gray, but on color negative film, apart from variations in contrast and blocked shadows, the colors have shifts both when reaching their shadows and highlights levels, and colors easily show -on not perfectly exposed color negatives- blue shift when underexposed, and yellow shift if overexposed... The best tonal range in the original is what I prefer, and what this thread is about... Thanks again...

    Cheers,

    Juan
     
    Last edited by a moderator: Aug 7, 2010
  13. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Robert,

    No problem here... Just the best and most beautiful sunny tones I've got from color negative film ever, after years of color wet printing and scanning... Now I think best color negative results depend a lot on precise exposure. That's all... And yes, I spent years correcting on enlarger or photoshop, and exposing in a more relaxed way... But from now on it's another story at least to me... Thanks!

    Cheers,

    Juan
     
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  15. markbarendt

    markbarendt Subscriber

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    Okay, so it seems apparent that you are scanning your work.

    That means we are talking apples vs. oranges.

    Scanners are one trick ponies as far as exposure and their exposure range and filtration is not normally used during the second exposure, software is, so sure your results may be different for different exposures.

    I say this because discussions here at APUG center on traditional photographic processes, scanning/hybrid methods are a different world and they off topic here.

    I shoot some with a Holga and Portra so I take many exposures "as they come" since aperture and shutter speed are fixed. The only exposure control available is picking the film or using ND filters.

    With an enlarger once I get the basic filter pack right for a Holga roll, all but the most extreme under or over exposures fall right in line for color temp.

    What I think you are seeing and describing in this thread is the limit of the scanner/digital process.

    Again, that is off topic here. These hybrid discussions are welcome at http://www.hybridphoto.com/forums/home.php
     
  16. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Mark,

    I think all this is in the right forum, as these variations are indeed present on color negative frames: their existence is purely analog...

    If you contact print a 6x6 strip of Portra 160 VC shot at -1, N, N+1 and N+2, you can see both contrast differences and color differences. Color negative is not a magical media: it's a simple light sensitive media, and it produces different color results -with a certain variation- if you give it X light or eight times that light... How could it be just the same after such a huge difference?

    But if your opinion is that all frames are color identical, your opinion is valid here too... This is how internet forums are...

    Cheers,

    Juan
     
  17. Robert Budding

    Robert Budding Member

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    I know this is a hybrid topic, but it still uses film, so here goes:

    Juan - you may want to try the CF Systems ColorPerfect Photoshop add-in for inverting and color correcting (earlier version were named ColorNeg). I've found that it works much better than any other method that I've tried. More info here:

    http://www.colorneg.com/oldneg.html?lang=en
     
  18. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Robert,

    Thank you very much for the link: it looks interesting...

    Generally I scan just to be able to decide which frames I prefer, but when I decide it, I ask my lab to do a real scan: their color depth is better because they use a real fine scanner... Sometimes I use their drum scanner, but even their very expensive flat scanner is way above consumer grade scanners...

    The color variations I'm talking about are subtle, of course... I guess people without wet color printing and enlarger filtering training wouldn't see them clearly... From -1 to +2, gradually, we're talking about what on slide film can be produced by a very slight warming filter on an overcast day: a small but decisive variation...

    I just expected here on APUG I would get more comments really related to my first post: tonal and color temperature variations ON FILM depending on precise metering and exposure, but it seems most people just filter digitally or in an analog way, and seldom they worry about "seeing" what's on film...

    After more than 200 views (or forum members) some comments came, but none of them did add anything on the subject...

    To exaggerate a bit, and leaving aside the best comments, I had "exposure doesn't matter, you get the same on film" and "go to other forum" answers... (!)

    Cheers,

    Juan
     
  19. Tim Gray

    Tim Gray Member

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    I think 'seeing what's on the film' is difficult because color negative needs to be interpreted in the printing stage. Without a consistent reference in each shot, isn't it hard to pick apart whats really on the film in terms of an overall cast?
     
  20. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Tim,

    Changes are evident on neutral tones going from cold to warm, even if on direct negative viewing we can't see them...

    I don't think color negative film gives the same result from -2 to +3. In fact, it doesn't give the same result within a single stop exposure difference... Anyone can test it with a pale gray subject: there will be changes no matter if you contact wet print a strip, or scan frames.

    Yes, we can filter afterwards, and we have a certain field of action within maybe one to two stops, but certainly different amounts of light affect color negative film's contrast and color temperature.

    Cheers,

    Juan
     
  21. Tim Gray

    Tim Gray Member

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    Agreed that different amounts of light affect things. Different types of light will also give different results.

    That's why its hard to figure out what's going on when there are too many variables changing. If you shoot a gray card in your light, and vary exposures, when you balance the colors for the gray card, you can see that maybe with XX exposure, the shadows are cooler while the highlights are warmer, while at YY exposure, the opposite is true. Or whatever the specific findings might be.

    When I say gray card, I don't mean JUST a gray card, but maybe a model holding a color checker, or something along those lines. A realistic scene, but with a known reference in it.
     
  22. markbarendt

    markbarendt Subscriber

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    Juan,

    Sure when the -1, N, N+1 and N+2 frames are printed all at once on one piece of paper they will obviously look different, so what? That's just a brightness issue.

    If you adjust to print each 6x6 frame on that roll separately with "individually appropriate" enlarger exposures designed to place the main subject at the same brightness level on the paper each time, the color balance/temperature will be quite stable between all the prints.

    Careful camera exposure is a good thing that can make printing more standardized and easier but it does not magically fix or change the color balance.
     
  23. 2F/2F

    2F/2F Member

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    Others have probably mentioned this already, but exposure certainly affects color. It affects color because it affects tonality, and with color film, color comes from tonality. In a color negative film, there are multiple layers of what is basically black and white film that you develop. The color simply rides piggyback on those black and white layers until the silver is removed in the process, leaving only the color.

    So, color film has curves just like b/w film, and exposure affects where certain parts of the picture land on this curve. However, it has three curves (or more in a four color layer film), and they don't exactly line up with each other. If anything lands off of the curve (i.e. to the left - underexposure) on any one of the layers, having full control of color balance becomes impossible. Landing to the left of your curve with a color film would be like a painter running low on one of the primaries. Your palette and your control are reduced. Thus, if you shoot in anything very far away from the color temperature the film was designed for, one or more of the color layers can be underexposed, and you should overexpose the film to help with color balancing later.

    When shooting 800 color neg film in tungsten illumination, I try to give an extra stop of exposure when I can. It is often difficult, however, as the situations in which I use this film, and in which I shoot in tungsten illumination are generally dark. The loss of a stop hurts or is simply impossible to achieve in these situations. This being said, however, IME Fuji films with the fourth color layer are incredible for low and mixed light. They color balance very nicely even when underexposed.
     
  24. Juan Valdenebro

    Juan Valdenebro Member

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    Hi Mark,

    1. No. It's not about brightness. It's about color: it's about the limits a light sensitive color media has when representing a real color and its real transitions to that same color when it reaches its own shadows and highlights... That color representation on film requires a precise amount of light: a bit less light or a bit more light produce, ON NEGATIVE, different color shifts. Forget the next steps: wet printing or scanning. Those are not discussed here... Use them as you prefer... This thread's about what happens to film. And if you don't have information on this subject, or believe the amount of light has no incidence in color or color temperature visible on neutral tones, you have the right to that opinion, but you're adding nothing to this thread.

    2. No. Not even filtering differently we get identical results. They can be close if the used exposure values were close, but with -1 and +2 (those values the masses believe valid and "the same" for color negative) you can't get identical prints... You can try to get a similar color in a subject, but other colors of the spectrum will be different. That's usual when you filter for similar skin tone in frames shot in autoexposure (exposed differently): you can get similar skins after filtering every frame differently, but other colors will be evidently different, and sometimes even the whole natural sunny mood can be lost after trying to correct with filtering what wasn't properly done with precise exposure and filtering when shooting.

    3. Wrong. Magic in your imagination only: to me this is predictable and stable 100%, a science... This is just optics and chemistry... As C-41 is a standard, indeed it's careful exposure and filtering on camera PRECISELY what produces the best color once and again.

    Cheers,

    Juan
     
  25. Juan Valdenebro

    Juan Valdenebro Member

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    Good points!

    Cheers,

    Juan
     
  26. Ken N

    Ken N Member

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    I love the Portra films, but mostly use the NC varieties because I use them for wedding and portrait work where they really shine. The VC films have much more punch to them, but I find the skintones to not be as controlled. But when it comes to getting maximum color with beautiful skintones, the VC films are not to be beat.

    Exposing the films is a little bit of an art, though. To keep this on-topic, I do both optical printing as well as digitizing--but mostly digitizing for combining the images in with digital-capture images, mixing and matching them and outputting the final files to the commercial lab for printing via the chemical process. The optical print versions really don't offer much that the digital process doesn't. A couple of years ago the Portra films were changed to better handle the scanning process. This had a minimal effect on the optical printing ability, but it did change things a little bit. But the new base is much better for scanning. In a calibrated environment, it doesn't matter if it is scanned (apples) or optically printed (oranges) because the end result is going to be similar--except in the extremes of the shadows and highlights. Kodak, however, has done an amazing job of getting the film to work in either environment exceptionally well.

    Exposure of Portra films depends a lot on your lighting. For example, if you are using flash/strobe lighting, I highly recommend shooting the film at exactly the rated film speed. This is important with the VC films because the highlights will block up easily. Same thing when shooting outdoors in sunlight--shoot it at the rated film speed. But where you will want to adjust your exposure is when shooting under incandescent lighting which causes the blue-sensitivity layer to effectively underexpose by at least one, sometimes two stops. Adjusting your exposure by a full stop will usually give yourself enough density to keep the blue layer from getting noisy and losing dynamic range once color corrected.

    This is NOT a Hybrid-Photography topic, this is a discussion appropriate to this forum. It isn't about the post-process, but the exposure of the film and the characteristic curves of it that make it a valid discussion point.

    Ken Norton
    www.zone-10.com