There's no RGB curve tool in ACR
Not with curves, but you can do a great deal of individual color tuning using ACR's HSL / Grayscale panel, which has luminance, saturation and hue subpanels, each with slider adjustments for colors and color combinations.
Of course you can, but not each channel individually, that was the question
vicente62, as others have noted, it is not possible to edit a single histogram channel with the current tools. Out of curiosity, what are you trying to accomplish? Do you have an example image where having this ability would be useful?
Hello.I will, in some cases, adjust the three channels independently. But now i'm seeing that it is difficult to do with Camera Raw.Thank you.
I understand that, but why? What are you trying to accomplish? If you're trying to fix specific problem colors, have you tried using the HSL controls with the Target Adjustment Tool (TAT)?
I understand that, but why? What are you trying to accomplish?
May I chime in...
I've been following the "get me RGB curves in ACR" debate for some time, and in my opinion, the top 3 reasons for asking for this tool are:
1. For effect. People want to simulate cross-processed film or simply a specific film "look". In other words, people want to distort on purpose the more or less technically correct colors as rendered by ACR defaults. This can be somewhat faked with the Split Toning, but you can't move the black and white point (note the crazy red and blue curves on the sample below). Moving the extreme point of a curve is crucial to achieveng a realistic cross process look.
2. To correct color cast. Sometimes adjusting the white balance is not enough for some photos that a shot in difficult lighting coditions (e.g. colored light sources, underwater etc.). The white balance tool adjusts the white point only. However, more complex and sophisticated curve shapes are requited for a photo like the one below.
3. "Black" balance. This is not normally needed for digital raw files, but for misdeveloped film or faded scans of old photographs is crucial to be able to adjust the black point on each of RGB channels separately. Also, it seems to me, a special case of this third reason could be useful even for digital files: Neutralizing the colder blacks shot in a shade (the Tint slider in Calibration does not help here) or getting rid of "blue blacks" of very high ISO images shot in tungsten (see an example in this post).
In the end, I would like to mention that I generally like the ACR/Lightroom design philosophy of keeping things simple for the user and letting "the magic happen under the hood". As I understand the RGB curves is considered a complicated specialist tool and not having it in ACR is a part of the design philosophy. And It works most of the times. But still, there are cases when you cannot do things without this universal correction tool, which might seem difficut for a newcomer, but is a well understood andpowerfil instrument in the hands of a user with 10+ years of Photoshop experince.