Advice for using CPL?

I'm sure I'm not the first person to experience this, I have a hard time seeing through the viewfinder what affect a CPL is having. As I rotate the filter I can sometimes (but not always) see the image darken (I assume that's near the point of maximum effect, based on the relative position of the sun), but that's about it. I've played around on several occasions and can definitely see a difference once I'm looking at photos on the computer, but really have a hard time predicting what an image is going to look like ahead of time. (By the way, I'm using decent filters... I have a Marumi DHG Super and a Hoya Super - I'd think they're plenty good for my level of experience).

Try looking through the viewfinder at a window (preferably outside) at an angle. That will demonstrate what is going on far more obviously

If I remember correctly point at your subject and your thumb at a 90 degree angle place the sun there and try it , you should be at 90 degrees to the sun again I may be wrong .

Read here

https://photography-on-the.net …/showthread.php​?t=1201798

If you have or make a mark on the CPL, you can also hold it up freely to your eye and turn it for the effect you want. Make a note of its orientation. Attach to lens and turn it to the same orientation as when you were holding it.