I'm new to CPL. Bought a decent one (b+w xs-pro 82mm) and tried it the other day. I rotated the front such that my foreground appeared more saturated with less glare. What I noticed was that the sky was partially/unevenly darkened. I was not using an ultrawide lens. I was at 24mm. The sun was more or less over my right shoulder, 90 degrees to my camera axis. How can I saturate the sky more evenly? I'm sure it's a matter of technique and not a fault of my CPL, and I'm hoping someone could shed some light. Thanks for your help.
It's uneven because the area near the sun will naturally be brighter. Nothing much you can do except shoot at a different time of day. GND will not solve the uneveness. You could recover highlight detail in the sky using software. I usually over expose the sky a little in favour of foreground then pull the sky back using a combination of highlights slider, curves and a grad filter tool if needed. Somtimes I might dodge and burn areas too. Use the HSL panel to tweek the blues back to a deep blue color. Adding a slight vignette also helps darken the sky. (This all works in conjuction with a CPL).
By doing it in post you have more control and can even it out a bit.
Btw how much of a difference are we talking about? A little is normal and natural for a landscape shot. Especially if there is a lot of sky in the shot. A plain blue sky of one tone is kinda boring anyway in my opinion.