Dimming a color generally reduces its perceived contrast, both in terms of brightness and hue. When colors are dimmed, the difference between the darkest and lightest parts of an image or scene is lessened, leading to a decrease in overall contrast.
Here's why:
Brightness Contrast:
Dimming a color reduces its luminance, making it darker. This decreases the difference between the dimmed color and other colors in the scene, thus reducing brightness contrast.
Hue Contrast:
Even with the same hue, dimming a color can reduce its perceived saturation and vibrance, making it appear less distinct from other colors, and thus reducing hue contrast.
Overall Contrast Reduction:
Because both brightness and hue contrast are reduced, the overall contrast of the image or scene is diminished when colors are dimmed.
For example, if you have a bright red and a bright blue and then dim both, the difference between them (both in terms of brightness and how "red" and "blue" they appear) will be smaller, resulting in lower contrast.
Did this and my phone screen is more pleasent to my eyes.