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Is there a method to change the luminosity of all pixels in the image as demonstrated below?

enter image description here enter image description here

  • What do you mean luminosity and tone? On your screenshot you're changing brightness, tone is lightness: you can't change brightness without affecting the lightness. To change brightness you can run Image > Adjustments > Brightness/Contrast – Sergey Kritskiy Mar 25 at 16:58
  • Hi. Welcome to GDSE. The images you have posted only show the colour picker. What is the actual effect you are trying to achieve. Do you have an example image? – Billy Kerr Mar 25 at 17:35
  • @SergeyKritskiy Sorry, I might have used the terms incorrectly. Increasing Brightness via Brightness/Contrast changes the colour saturation(?) - eg. from the colors picker the color goes to left or right. I need it to go only up and down. – Arturs Mar 26 at 13:53
  • @BillyKerr Sorry, I do not have an example. But the color pickers show exactly what I would like to happen to all pixels in the image. I would like the color to move vertically up to brighter, but do not change its horizontal position. – Arturs Mar 26 at 13:55
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You have increased the brightness number of the color when an RGB color is presented in Photoshop's HSB system. You have kept hue and saturation intact.

I guess you want either change the brightness number of every pixel by a certain increment or multiplicand upwards or downwards but keep H and S numbers.

Actually it's not 100% clear in the question what you want. Luminosity is totally something else, but you have increased the brightness number.

Photoshop doesn't have such slider. All adjustments are developed to appeal photo editors or at least Adobe tries to present them as intuitive natural controls for photo editors and they strictly do not publish any numerical functionality data. Do not expect that image adjustments Hue&Saturation (or actually the lightness slider) or Brightness&Contrast (in either of the modes) do the job. There's also no easy way to get it with Curves.

Without being able to show any Adobe's numerical data as a proof I suggest you try at first the Exposure adjustment. It seems to be better than Hue&Saturation and Brightness&Contrast for this problem. Let the gamma and offset sliders be in the middle.

A more exact way:

In the filter category "Others" there's a filter which digs HSB numbers of every pixel and places the result to red, green and blue channels of the image.

You can use it. Then you can add or subtract a certain number from every pixel in the blue channel or multiply by a certain number. Both of these transformations can be done with curves or levels.

Finally you recompose the RGB channels by using the HSB filter reversely.

It was complex!

If you want to bring all pixels to same brightness without changing hue and saturation you can turn the curve to horizontal. But there's an easier method for it, but it's not in Photoshop. Use GIMP There's layer blending mode "Value" :

enter image description here

The test layer is pasted from Photoshop. It has 3 color zones with the same hue and saturation. Brightnesses from the left are 100%, 75% and 50%

The 100% bright color is copied to fill a new layer and the layer has got blending mode Value:

enter image description here

All zones have now the same 100% brightness. That's because Value in GIMP's RGB system means the same as Brightness in Photoshop's RGB system. The next image is only to show that the effect works with other colors, too:

enter image description here

Is the effect usable for something? I do not know, but here's an indoor shot of an old workroom in a small local museum:

enter image description here

This is the same, but every pixel is lifted to about 93% brightness without changing hue nor saturation:

enter image description here

There's still remarkable lightness differences because the Brightness (=Value in GIMP) is the highest of the RGB numbers as percents of 255.

Maybe asked or not: Color vision theorists have found 100 years ago that humans can in their mind separate from a color hue, lightness and colorfulness components. RGB color system or it's polar math versions like HSB are extremely poor in that sense. Some hues look much more colorful with the same saturation than others. In addition the apparent lightness changes when one changes the hue. That's because HSB is a way to control RGB screens, visually uniform colors are not a design goal. Saturation only shows how much variation there's in the RGB numbers as a percentage of the maximum, its not the apparent colorfulness.

Photoshop has color mode Lab (=CIELAB in more scientific texts) which is far closer to uniformity. If you convert your image to Lab color mode and adjust Lightness with Image > Adjust > Curves > L channel you keep the hue and the apparent colorfulness except in case you try to generate a color which would need on the screen RGB numbers less than zero or more than 255. Custom gamut warning in the View options can reveal undisplayable Lab colors.

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  • Thank you for your elaborate response. I agree I must have used the wrong terms. I was trying to achieve this with Brightness, but it actually moves the color to left/right in the RGB colors picker. I would like for it to stay horizontally where it is and only move vertically. – Arturs Mar 26 at 13:58
  • Exposure moves it horizontal less, but I have tried it only with few colors, It can only look good in my tests. The HSB filter is a mathematically exact solution for your problem. – user287001 Mar 26 at 14:01
  • I agree, however, exposure will start clipping at over-exposure point. I was wondering if it was possible for the color to stay at its topmost position as in my colorpicker image without tilting towards white overexposure. – Arturs Mar 26 at 14:04
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    @Arturs The answer covers now it, too. – user287001 Mar 26 at 14:42
  • I will look into this - thank you for your help! – Arturs Mar 26 at 17:11

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