Colored lights, blinkies and single channel clipping

Discussion in 'Open Discussion' started by Klorenzo, Jun 17, 2017.

  1. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    I've shot a few theatre shows recently and I encountered a new problem, mainly with colored lights.

    For exposure I used the blinkies as a reference to avoid highlights clipping keeping the exposure down as much as needed.

    The situation is that in several shots, with different lights, I have one single channel that extends much much more into the highlights than the others. Here three samples:

    According to Darktable only the blue shot has some small clippings in the RAW file. According to the E-M1 LCD everything is ok (in the jpeg rendering luminance I suppose). The only hint is in the small colored histograms where one is clearly different from the others.

    The problem is that as soon as I try to recover some shadows the blown channel gets clipped and the colors get weird. If I push only the other colors, or push down the red, I get a similar problem. I do not want to alter the light color, just to open the shadows.

    How do you deal with this situation at show time and in post? How to notice this problem while shooting?

    I have already exposed to the left, exposing even darker would make no difference as the difference between the channels would be the same. Exposing for the shadows would just clip completely the blown channel. Seems more like a dynamic range problem.

    The blue shot is not bad (I have others with the faces pointing up where I get the same clippings I get on the white shirts). Recovering the highlights, that should be easy, does not work very well, probably due to minor clippings.
    The two guys shot is overexposed, pushing it down by about 1 stop makes it more natural (and the red channel is all inside the histogram) but the guy on the left is lost in the shadows.
    The girl shot is not bad but to lit her face is impossible. Here I think the light was near white, probably a little yellow. The red sweater explodes into orange as soon as I do anything. Using a lot of work with selective color correction I was able to do something but nothing really usable.

    I'm not interested in these shots specifically, these are just a sample (from the bad ones). I also do not like the "all shadows full open and all highlights down" style that is so common in many shots around, I like some natural contrast, but a little correction sometimes helps.

    What do you think?
  2. christofp

    christofp Mu-43 Veteran

    Jul 21, 2012
    I trust the blinkies for white objects like clouds or flowers. Checking the exposure with RawDigger, for ISO low and ISO200 it is spot on.

    But for colored things, especially for red ones like red roses or sunset, I dial the EC to the point when the orange blinkies appear, press the AEL button and dial EC two or three steps back. So, for colored opjects, I leave 0.6 to 1EV headroom and this way I don't get any clipping issues ...

  3. Hendrik

    Hendrik Mu-43 Top Veteran Subscribing Member

    Feb 27, 2015
    Wayland MA
    I don't know enough about Darktable to suggest a way out. I can report that it is possible to get reasonable renditions in Adobe Camera Raw by pulling back on the Whites slider as well as the Contrast slider and pushing Shadows and, perhaps, Blacks with the Highlights and Exposure sliders adjusted to taste. The major problem this approach creates is the noise that becomes apparent in the backgrounds, but this is pretty easily dealt with in Photoshop using layers and masks. The downside, of course, is that the masks must be individually constructed - a major pain.

    On the shooting side of things, I have fallen into the habit of using the RGB histogram and neglecting the blinkies. I also redefine Histogram clipping at each end, Highlight 251 and Shadow 4 (Gear D). Doing this, I find I can generally avoid single-channel blowouts, if that's what I want to do. Balancing highlight and shadow detail/clipping is an art and not always possible.

    Theatrical lighting is really tough. The girl's face displays at least a three-stop difference between the specular highlight on her forehead and the shadow on her temple. Given my choice, I'll take undramatic, even and moderately dim interior lighting any time.
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  4. junkyardsparkle

    junkyardsparkle haunted scrap heap Subscribing Member

    Nov 17, 2016
    like, The Valley
    Sometimes I find it useful to use the monochrome module, biased towards the opposite color as the lighting, and then blended to taste with one of the various modes that retains color... for instance like this for the yellow light (wasn't sure if you wanted the images posted here or not).


    You can of course combine this with whatever other methods for shadow lifting you like... I personally find that using multiple approaches in smaller quantities looks better to me than leaning on any one slider too heavily.
  5. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Thanks for all the answers.

    Usually, I really cannot chimp after each shot as the light may change or the actor may simply move in/out of the main lights. Or maybe I could but I'm not so fast and relaxed yet. And I'm spoiled by the mirrorless magic :) I usually do like christofp said: AEL, look at the EVF and drop down one or two clicks to make the blinkies go away.

    This is the best I can get and I'm not unhappy, especially considering the lighting and the ISO. It took a lot of masks:



    The thing that bothers me most is that they never look "right" or "good" (the first one is fine, different problem there). In the last shot the skirt is too dark but if I make it even brighter it is too bright. The sweater is too....weird. The skin is pale and green-ish but if I move the tint towards magenta it gets worse. I think it's just the light colors that tricks me, while I try to find a pleasant look while keeping the lighting work as is. And moving only the medium tones to avoid clipping (and posterization) (and noise) (o_O).

    Darktable corner: @junkyardsparkle@junkyardsparkle good to find a fellow DT user :) I tried with the monochrome but it removes too much saturation for my tastes. Sometimes I got good results doing the same thing with the colorize module. Here are my processing files if you are interested.
    BTW, off-topic, do you know any good way to remove large chroma noise halos? I use a lowpass filter (3px, color) for the small dust (sometimes hotpixel too) and equalizer for the halos but this one removes some saturation and shades too (that I later try to put back with "vibrance" but something always gets lost in the process). Denoise profiled (wavelets, blend: chroma) works fine chroma noise too but sometimes does not catch the wider halos and adds quite a bit of extra grain (that I later denoise...).
  6. junkyardsparkle

    junkyardsparkle haunted scrap heap Subscribing Member

    Nov 17, 2016
    like, The Valley
    I had a chance to play with this a little, I took a shot at the "red" image, since your versions of the other ones looked pretty good to me already. I really hate drawing masks... it's tedious, usually ends up looking unnatural to me, and you can't apply the work to a series of similar images... so this is a quick attempt to roughly match the overall shadow lifting of your example, but with more natural skintones and less odd flattening of the lighting (trying to work with the extreme lighting rather than against it). No drawn masks, very few modules used, most of the heavy lifting done by the "tone mapping" module, some ramping down of high saturation with "color zones" (love that module!) and tried to use the "RAW black/white points" to eliminate the hot pixels rather than any fancy algorithmic stuff that doesn't ususally work as well. You can grab the XMP here:

    Darktable RAW processing example data for red-clipping-P6110324.ORF · GitHub

    Even if you don't like it as-is, it might be worth using as a starting point for exploring more holistic methods of processing - see if you can get what close to what you want by adjusting the already active modules, maybe. I didn't do anything heroic about noise, just toned down the default "profiled denoise" a little, so you may want to finesse that a little (the upper-right corner lights are a little splotchy, in particular). Sorry, elaborate noise fixing isn't my thing, I'm usually happy as long as chroma noise isn't too bad, and leave it at that. :D


    EDIT: Taking a second look at it, looks like the "color zones" module needs a little more adjusting to smooth out a few of those red areas... but hopefully you get the general idea of what I was working towards, anyway...
    Last edited: Jun 19, 2017
  7. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Seems good to me, the skin's a little too red/magenta maybe but removing that means to remove the light color. The sweater light is also softer and the red is also not over saturated like the one from the oly rendering below.

    I love rougly drawn masks when combined with parametric masks: you can select oddly shaped things in a few seconds, like the white shirt using a Luminance e Chroma mask (the smaller color picker tells you where to aim). I've never used the tone mapping and the "RAW black/white points", Color zones "by saturation" is also worth a little study.

    This is exactly the problem! Everytime you look back at the shot you'd change something :)

    These are a few more shots from the same show to give you a better idea of the whole mess (OOC jpegs):





    Matching the colors for all of these (including the blue blanket) takes a lot of patience...
  8. PakkyT

    PakkyT Mu-43 All-Pro

    Jun 20, 2015
    New England
    Ok so now I am confused. If the AEL purpose is to lock your exposure, but while holding it you then turn the exposure compensation back a click or two, shouldn't it not work since you are supposed to be locking the exposure (how do you compensate the locked exposure)?
  9. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Well, it locks the camera, not the human :) The exposure won't change unless you say so with exp comp.

    Normally the camera is constantly metering the scene and correcting the exposure parameters to its liking. If you pan the camera around you'll see the free parameters jumping around as you frame bright or dark subjects. AEL means: ok, current one is good/reasonable, stick to it. From there you start your fine tuning.

    For the same reason, it is quite complex to use exposure compensation if you do not lock the exposure first: you are going to compensate on a moving target. As soon as you reframe you risk to loose all your hard work. Even more with center/spot metering.
    If the scene brightness is quite uniform or you do not reframe you can skip the AEL step, but if you are going to take 100 shots of the same scene you really want to be able to reframe/zoom freely.
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  10. PakkyT

    PakkyT Mu-43 All-Pro

    Jun 20, 2015
    New England
    Ah OK I see what you mean. First I didn't realize AEL would allow manual overrides while engaged (at first blush it seems counter intuitive). And second, now I see what you guys were getting at is setting a "base level" exposure (which might not be what the camera always wants to use) and then you can adjust from there. But always going back to +0 puts you back at that base level, NOT what the camera currently might want to put it at.

    Thank you.
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  11. junkyardsparkle

    junkyardsparkle haunted scrap heap Subscribing Member

    Nov 17, 2016
    like, The Valley
    Yeah, the shadowed parts are being "lit" by reflected red light, I just white balanced for the stage light. My lazy minimal-processing sensibilities tell me that the reddish shadows are reddish for a reason, and that they look fine. ;) I just don't like "fighting the light" with PP, I seem to usually just make things look differently bad, if not worse... of course, the overall WB tint might be biased away from green by a tick or two, I tend to do that.

    I totally agree that the drawn + parametric is an awesome capability (or even just drawn + the selectivity parameters built into some of the modules) even if I avoid using it as much as possible. Definitely don't be afraid of the "tone mapping" module, despite all the horrible things the name (and the default setting) might conjure up - it's actually quite useful for non-horrible stuff, too, given some restraint. Might be a much faster way for you to get to a good starting point for whatever additional stuff you feel is needed. The RAW w/b points aren't something you normally want to mess with much, but in this case was usefull for dealing with those "hot" specks that were just above the threshold... aaand, adjusting saturation BY saturation is really just the chroma version of a tone curve, right? :D
    Last edited: Jun 20, 2017
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