How are the numbers related to the RGB values

Hello,

Please take a look at the attached image.
I am in the process of removing luminance noise, and I want to denoise the slightly lighter background without blurring the darker bird too much.
I have somewhat managed to do that with the current curve, but I could use a vertical RGB guide line as it exists in the equalizers - in order to decide where the curve should change.
The bluish feathers are in the 20’es (as the RGB percents show left). The greenish background is from 30 to 35%. It’s a rather delicate interval and a guide line would ease the process.
Further I am not sure how to relate the i-o numbers to the RGB %s.
Help would be much appreciated.

Best,
Eigil

I don’t think there is a direct relation between I/O and RGB (or HSV/L*a*b).

The I slider (X-Axis) is full black (0.0) to full white (1.0), the O (Y-Axis) signifies the intensity: none (0.0 to full (1.0).

The horizontal axis does seem to have a relation to the L channel.

Thanks, Jacques,

A vertical guide line showing the tone for a given position would not be in conflict with the concept and the continuous grey scale in the bottom of this window - as far as I can see.
Could that be a consideration among the developers?

I doubt that. I always thought that X signifies luminance and Y intensity. I looked it up just now to be sure. This from RawPedia:

The curve has the additional advantage of letting you control noise reduction strength as a function of the pixels’ luminance - e.g. it allows you to have strong luminance noise reduction in the shadows and none in the highlights.

If you want to tackle noise in a specific colour range you might want to have a look at the Local Adjusments tab, which can do this.

Set one or more spots (using spot method - Full Image) based on colour and attack the noise using the Blur/Grain & Denoise tool.

EDIT: @Andy_Astbury1 did a video about how to approach this:

If you want/need an example to play with, I tried out this method in this edit:

Just related to luminance. SImple example here of how to use it from rawpedia…

image

Jacques:

Actually I meant Luminance (saying “tone”, sorry) - as opposed to color.
And as you stated - the horizontal direction takes care of Luminance, which in my intuitive understanding is represented by the continuous greyscale.
In my explanation I refer to luminance or lightness, and I tried to shape the curve to my perception of the luminance-difference between the two circles.

I have experimented a lot with noise reduction in the Local Adjustments tool.
It’s good for many things, but sometimes the background has too many colors which results in a number of circles interfering with each other.
This images would probably be a good candidate for a local denoising adjustment, but my attempt here was to investigate the features of the luminance noise curve - and I imagined a luminance guiding line would have served me well.

If I use your posted screenshot I see that there is a +/- 13% lightness (L channel) difference that you might be able to use to your advantage:

Not sure if this actually translates fully to 0.441 / 0.311 on the X axis, but you will probably be close if you do use those numbers.

Yeah, that is true. I’m reasonably good at using the Scope and shape detection tools to limit the area that is targeted, but this isn’t a full-proof method. Sometimes it just is what it is.

1 Like

I know exactly what Eigil is talking about - it would be a really handy addition to all curves, allowing you to see where any point in your images lies on a curve/equalizer. Handy - but not essential.

@Andy_Astbury1 : Yeah, that would be nice!

Being able to set points using the Lockable Colour Picker as well would be even better…

1 Like

I’ll try it out, Jacques.
Thank you.

Thanks, Todd.