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Thread: removing the effects of a yellow filter from a color negative scan

  1. #1

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    removing the effects of a yellow filter from a color negative scan

    Hi all,

    So I was out shooting the sunset a couple of months ago with B&W and color film. I forgot to remove the yellow filter from my lens when switching film holders from the B&W to the color film. When I got the color negative film (Kodak PORTRA 400) drum scanned (the sunset was beautiful) I discovered my mistake. I tried using the Photo Filter set to Violet around 45% in PhotoShop CS5 to remove the yellow cast from the image. While I succeeded in removing the yellow color cast, the image became much darker. And I am having difficulty lightening up the image without the image becoming flat and almost monotone. Does anybody have any suggestions on how to remove the yellow color cast without darkening the image?

    I am attaching 2 images: 1 with the yellow color cast and 1 without (I at least had the sense to make a 2nd exposure!).

    Namaste
    Daniel
    Attached Thumbnails Attached Thumbnails Sunset-CathedralRock-YellowFilter.jpg   Sunset-CathedralRock.jpg  

  2. #2

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    Re: removing the effects of a yellow filter from a color negative scan

    I assume the image file is not a RAW file. I'd first start by opening the image in Camera Raw
    file>Open in Camera Raw
    and experiment with the sliders.

    Unfortunately I believe that you lost a lot of color information to begin with in the blue sensitive layer (don't quote me on that since I haven't printed color negative film since the 1980s).

  3. #3
    Lachlan 717
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    Re: removing the effects of a yellow filter from a color negative scan

    I'd actually enhance the warmer spectrum -yellow through red.

    Fighting the lack of colour information in the rest of the spectrum will be pretty much futile.
    Lachlan.

    You miss 100% of the shots you never take. -- Wayne Gretzky

  4. #4

    Re: removing the effects of a yellow filter from a color negative scan

    Since Portra is so forgiving and has no real issue when you expose it with tungsten rather than daylight, assuming it was a weak yellow filter, a good drum scan should have no problem with it. Unfortunately, this is not a good scan and I hope you didn't pay for it. I would try having it rescanned by someone who knows how to scan a color neg. It'd be better if you can be there to see the rendition on screen in the scanner preview as it's such a subjective process. Also, you've posted an untagged file, which leaves its interpretation somewhat ambiguous.

  5. #5

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    Re: removing the effects of a yellow filter from a color negative scan

    Thanks for the suggestions. I guess it's time to be creative with yellow, orange, and red!

    Sasquatchian: yes, I did pay for this scan, and the above image is a reduced JPEG of this (drum) scan. And yes I did notify the drum scanner about the yellow lens filter and request that he do his best to remove the yellow color cast. And the lens filter was a Tiffen #8 Yellow Lens Filter, so pretty strong yellow. I am not sure what a tagged versus untagged file is, so could you please explain it to me (maybe other people want to know what this means as well)?

    Namaste
    Daniel

  6. #6
    Resident Heretic Bruce Watson's Avatar
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    Re: removing the effects of a yellow filter from a color negative scan

    Quote Originally Posted by DolphinDan View Post
    Does anybody have any suggestions on how to remove the yellow color cast without darkening the image?
    You can't. The yellow filter acts as a low pass filter. That is, it blocks high frequency light. That is, it blocks blue light. End result -- your film didn't record much blue light. Since it's not on the film, there's not much you can do about it.

    This is sort like baking a cake, then realizing you forgot to put any salt in, and asking how you can fix that now that the cake is already baked. You can't fix the cake, and you can't fix the film. Sorry.

    If you insist on jumping down this rabbit hole, you can try pulling back on the red and green channels to line them up with what little blue you have left. This will result in a desaturated and darker image of course. Not exactly what you want in a sunset shot. If you then "pump up" the saturation for the entire image, don't be surprised to see banding, especially in the blues.

    Bottom line, you didn't properly expose the film. Learn from your mistake and move on. You're not going to turn this sow's ear into a silk purse. We've all been there, struggled with that, and learned from our mistakes. Welcome to the club.

    Bruce Watson

  7. #7
    Peter De Smidt's Avatar
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    Re: removing the effects of a yellow filter from a color negative scan

    This is really a Dan Margulis type of situation. The biggest problem is how underexposed the foreground is. You might try this. Duplicate the background layer. Select that layer. Go into the channels palette. Look at each of the channels. As expected, the blue channel is awful. Chose the blue channel on the new layer. Go to Image>Apply Image. Apply the red channel to the blue channel. Press Ctrl+2 to select the composite channel on the layer. Now adjust the opacity of the layer to taste. You can try putting the green channel into the blue instead of the red.
    Attached Thumbnails Attached Thumbnails apply image.JPG  
    "Why can't we all just get along?" President Dale, Mars Attacks

  8. #8
    David Lobato David Lobato's Avatar
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    Re: removing the effects of a yellow filter from a color negative scan

    I gave it a try in Photoshop. First I added a curves layer with only the blue channel. Amped up the blue curve. Then set that layer opacity to 30%, use whatever amount you like. Then with opacity at 100% on the bottom and mid at 50%, masked the lower portion to remove the blue cast in the shadows. Then added an RGB curves layer to darken the blacks, a levels layer will do the same thing.

    Last edited by David Lobato; 20-Feb-2017 at 09:09. Reason: clarify the process

  9. #9
    Peter
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    Re: removing the effects of a yellow filter from a color negative scan

    As has been suggested, you might be able to fix this with a better scan. I made some curve adjustments (to the yellow file) and posted them along with the image. There seems to be a light leak at the lower left corner and some color shift along the bottom and left side from the leak.

    Click image for larger version. 

Name:	Sunset.jpg 
Views:	15 
Size:	76.7 KB 
ID:	161618

  10. #10

    Re: removing the effects of a yellow filter from a color negative scan

    There are a few things here. First, there is a fair amount of information in the blue channel, and you can use Calculations to build on that. In addition, some judicious Channel Mixing helps as well. I still think that this is a very substandard drum scan. I also think that it's not a light leak at all in the lower left, but it's a common drum scanner artifact that often happens when you have a misaligned optical path and you don't mask off the film on the drum. When you manipulate the file, you also see light encroaching on the other edges of the frame. I discovered this when I got my second drum scanner - a Howtek HR8000, but I've seen the phenomenon on other makes and models as well.

    I spent a few minutes on this image, and mind you, at home on a MBP, but you'll get the basic idea. I approached it as I would if it were my image to see if it was salvageable to something I might like. In the process I also saw some interesting silhouettes but left those buried in the layer stack.

    "Tagged" means embedding or TAGGING the file when you save it with the ICC profile of your RGB working space, i.e. sRGB, Adobe RGB, Don RGB, etc. Without an embedded profile, you either see the image in Monitor RGB or, depending on your browser, sRGB or some other designated color space. Embedding the profile removes any ambiguity about how you intend the image to be viewed, assuming you've got a hardware calibrated monitor to start from.
    Attached Thumbnails Attached Thumbnails Sunset-CathedralRock-YellowFilt_pf.jpg  

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