The original in 16-bit mode is linear 14-bit acquire using Umax PowerLook III scanner into Photoshop 15-bit space and then cropped.

Since the original is well saturated already let us see what desaturation does.

Decreasing the saturation in gamma space affects strongly to the hues that have low saturation and affects only slightly to hues that are highly saturated. In overall there are pleanty of hue shfits.

Linear space processing

1. Open the original linear higher bit-depth image.
2. convert to 8-bit mode.
3. decrease saturation by -30 using Hue/saturation dialog.
4. apply inverse gamma 2.2.
5. save as jpeg using quality factor 4.

Gamma-space processing

1. Open the original linear higher bit-depth image.
2. apply inverse gamma 2.2.
3. convert to 8-bit mode.
4. decrease saturation by -30 using Hue/saturation dialog.
5. save as jpeg using quality factor 4.