Strict Theoretical Color Separation in Photoshop – Is It Possible?

Thank you for your effort, sir — it's a very good attempt. However, I still notice a slight red and green tint in the gray gradation, which you can verify using a color picker tool. Additionally, the remaining gray areas don’t fully align with the standard grayscale conversion formula.

Thank you for your reply. I have already tested a similar approach in Photoshop. The result looks close to what we want, but only because the example uses solid colors that are easy to identify. In practice, this method isn’t reliable—especially when applied to gradients, as shown in the example below—and it becomes even more challenging when the colors are less defined or difficult to identify.

I expected someone to point out an option in Photoshop for this, but am I asking for something that’s too difficult to achieve?

Thank you for your response. I don’t think a Luminosity Mask would solve the issue. Even with a proper mask, it doesn’t address the core requirement: separating colors accurately—for example, removing red from orange so that only a shade of yellow remains—while still maintaining the correct luminance value for red (76, based on the standard grayscale conversion formula).

I’m sure there must be an option in Photoshop that can achieve this, as it’s a very basic feature. So far, I’ve tested Hue/Saturation, Selective Color, and HSL in Camera Raw, but none achieve the expected result.