How "preserve luminosity" works?

Dear all,

I used Photoshop and there is a "preserve luminosity" in Color Balance function. Anyone knows how the "preserve luminosity" works when e.g. user is adjusting the midtone of the color channels?

Thanks,
J.

wrote:

I used Photoshop and there is a "preserve luminosity" in Color Balance function. Anyone knows how the "preserve luminosity" works when e.g. user is adjusting the midtone of the color channels?

It lightens or darkens the colour so that after changing the colours, the apparent brightness is still the same. Luminosity can be calculated with:

L= 0.299R + 0.587G + 0.114B

(Our eye responds differently to each colour).

Cheers,
Nicholas Sherlock