Lightroom: RGB Curves

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I have no idea what kind of impact this has on Lr's dev editor design, but many of us would like this built into Lightroom if possible.
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Rob Cole

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Posted 9 years ago

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Lee Jay

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My version of PS (Elements 8) has red, yellow, green, cyan, blue and magenta under HSL while Lightroom has red, orange, yellow, green, aqua, blue, purple, and magenta. The stated reason for this is that this particular set of color separations better divide the colors we see in common images. Yes, I know about the sliders in PS that allow you to change the color range affected.

This makes me wonder if red, green and blue makes any sense like it did in PS when we were processing images that were already in an RGB color mode. Why not separate the colors in some different way, possibly more like HSL does?

I don't know if that idea has any merit, I'm just thinking out loud here.
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Rob Cole

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Dunno. I would say though that the more powerful *other* color adjustment tools are, the less RGB curves are "needed". I'd also say that editing RGB curves is about as "unwieldy" a way to adjust color is one could possibly get, and is consequently very un-Lightroom-like. On the other hand, it allows one to do things that would otherwise be impossible with the existing color tools. And maybe its not much more unwieldy than adjusting tone using the point curve.
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TK

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Rob, can you give (an) example(s) for what you would do with RGB curves?
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Rob Cole

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One way to think of it is it gives you the ability to adjust the white balance at all luminosities. Sorta like split toning divided into an infinite number of regions, instead of just two. There is more than one use for it, but perhaps the two most common are:

1. Correct for luminosity dependent color casts.
2. Creative color adjustment for effect.

PS - Its available in Aperture, NX2, DPP, CaptureOne, & Bibble, in case you want to try it for yourself.

There have been lots of good discussions about it on the other forum, unfortunately the search is broken there, and I can't seem to remember the correct syntax for using google to do it.

I may come up with some concrete examples for this thread at some point...
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TK

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Thanks Rob. These don't seem to be high priority items for me personally. Regarding Google syntax: "[search terms] site:[suffix of domain]", e.g., "RGB curves site:support.bibblelabs.com".
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Rob Cole

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I was able to restrict the search, but when I clicked the links, I was taken to generic forum pages with everything on them - I mustof done something wrong...

Anyway, RGB channel curves are not, specifically, high-priority items for me either. However, some better way to target and adjust color, is - I'm just trying to cover all the bases...
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Andrew Rodney

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IF the request has to do with the so called “master curve issue” I’d suggest this article (LR/ACR and Photoshop are different beasts as explained here):

http://www.luminous-landscape.com/ess...
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Volker Kunkel

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I would like to be able to use RGB curves strictly as an artistic tool, not for real color correction as there are already fine tools for that. But giving a bit more blue to the shadow area, while tinting the highlights to warmer tones and removing green from midtones is what curves really are fine for. As said before, not so much neccessary for getting the "real" colors but for mixing them up to create some old film look.
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Rob Cole

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I applaud your comment, but didn't see the vote count go up - are you holding out?
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Volker Kunkel

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simply forgot to click
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jdv, Champion

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Isn't this what split-tone already does?
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Joe Carver

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Well, split tone is useful for tinting highlights or shadows and it's all we have at the moment, but it is lacking in comparison to full rgb curves, which would give you complete control over the full range. Plus, I find the split toning color slider to be fiddly and limited- I would love to have colour wheels. I use them all the time in video grading and they are much more useful.
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Joe Carver

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Feature request: RGB curves in Lightroom 4. I would love to see the addition of rgb curve control (as in photoshop) added to lightroom 4, in mind mind this is one of the only features 'missing' from Lightroom at the moment, and not having this option limits the colour control regrettably.

I have never used Apple's 'Aperture', but have read that it does indeed have RGB curves- the only thing that gives me cause to think twice about my choice of product.

This reply was created from a merged topic originally titled
Lightroom: RGB curve control.
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John R. Ellis, Champion

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Here's a narrow use-case for allowing RGB curves/levels of slide scans to be adjusted separately. I fully recognize that it's not squarely within LR's sweet spot of digital camera images, though based on these forums, there are "many" people using LR to manage scanning:

I scan large numbers of Kodachrome slides that are 30-60 years old, using a Nikon LS-5000 scanner and Silverfast calibrated to a Kodachrome target. Using visual comparison, the scans seem very faithful. Both the original slides and the scans tend to have a modest red cast that can muddy the shadows, especially if I then adjust the tonal range of the shadows, e.g. by increasing Fill Light. This cast is readily apparent if you look at the LR and Photoshop Elements histograms:





The fastest, most reliable way to correct this is to move the black point of the red channel. Sometimes the LR White Balance Selector (eye dropper) can address this, but it's fussy and unreliable and I can end up in a pixel hunt for neutral tones. So I end up opening the scans first in PSE to adjust the red channel, then doing most of the processing in LR, and occasionally going back to PSE if there is dust, scratches, or fungal splotches that can't be fixed with LR's convenient but limited Spot Removal tool.

I don't know where this red cast comes from (inherent in the film or original processing or aging), but it's clearly visible on a large fraction of the originals.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Official Response
Per Channel Curves is in Lightroom 4:

http://feedback.photoshop.com/photosh...

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Rob Cole

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Awesome! - thanks be to Adobe...
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Joe Carver

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I saw! Excellent news! The dynamic range stuff looks good too
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Mark Alberhasky

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While I am primarily a LR user (and teacher) I do periodically run work thru Aperture to keep some familiarity for teaching. One of the features that I find quite powerful is found in how Aperture approaches use of curves. In that section of Aperture development there are option to automatically adjust curves, either all together or individually by color channel. The latter automatic curve adjustment is quite powerful and gives an often very good to excellent rapid achieved starting point more quickly and more easily than making comparable development adjustments in LR.

I'd really like to see synonymous functionality (auto curve adjustment by individual color channel) within the LR develop module toolset.

This reply was created from a merged topic originally titled
Lightroom: Channel Specific Curve Adjustments.
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Joe Carver

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I'd like to be able to reset individual colour curves without affecting the RGB curve. For example, if I have changed the colour curves and am applying the same settings to several photos but then decide to convert some to black and white, they will be tinted because of the colour curve adjustments. I can reset all curves easily, but I want to be able to keep the RGB curve as it is whilst resetting the rest.

It would also be handy to be able to quickly set handles to shape the curves, rather than having to place them manually every time.

I have been trying out Aperture 3, and despite it being an older product than this Lightroom beta, it is ahead in functionality in many ways. Lightroom 4 seems to just be playing catch up to some of these features (and I wish they'd focussed more on the actual editing tools rather than the extra modules, which I doubt will get any use from me). Even so, there are still things lacking. Eg. Aperture's colour wheels are a much easier and more accurate way to set colour than the sliders, and being able to set shadows, mids, and highlights puts it way ahead of Lightroom's split toning, which i have always found fiddly and difficult to find the colour I want.

Lightroom does seem way ahead with the noise reduction however, which is vital for me. But if the next version of Aperture can compete with this, Lightroom will certainly start to look less appealing. Whilst it's still my favourite for now, I think Lightroom really needs to add a little more flexibility to compete with some of Aperture's tools, particularly in the brush department. The added brushes in Lightroom 4 are very welcome (the moire brush can be very effective against CA fringing!) I hope we see many more of Lightroom's abilities available in brush form.
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Andrew Rodney

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I'd like to be able to reset individual colour curves without affecting the RGB curve. For example, if I have changed the colour curves and am applying the same settings to several photos but then decide to convert some to black and white, they will be tinted because of the colour curve adjustments.

Easily corrected with Saturation/Vibrance or HSL controls. The effect is built into the curves since it is desirable in most (more cases). Also see:http://www.luminous-landscape.com/ess...