Bad Eyes, or Bad Advice

[RCrosby]

Recently got a Lenscape circular polarizing filter for my S5. Had read somewhere that the linear wouldn't work with the S5 but have since been told that either would work.
At any rate, a Lenscape "techie" told me that one half of my circular filter was darker than the other and I should rotate it accordingly; i.e. dark half up if bright skies were the concern; dark side down if worried about reflection off of water or snow.
Try as I might I can't see any difference, either in the filter itself or the pictures I take and the advice sounds more appropriate to a linear filter.
So which is it? Bad eyes or bad advice?
Thanks,
Rob
file:///Users/teacher/Desktop/IMG_3870.JPG

[Jon]

Bad advice, or garbled in translation. Graduated ND filters are dark on one part and light on the other. Polarizers (circular or linear) need to be rotated as you watch the effect on the scene. To get the best idea of how this works, stand with your shoulder to the sun on a bright, clear day and look through the polarizer (threads toward you) at the sky as you rotate the filter. You'll notice the sky going from very bright, pale blue to a much deeper blue over 90 deg. rotation.

[RCrosby]

Jon,
Now I'm wondering if I may have gotten a mislabeled filter. I'm familiar with the changes observed in rotating a polarizing lens (from sunglasses) but I've tried any number of times rotating the filter against bright white clouds, blue sky, etc. and the difference just isn't there.

[msowsun]

It sounds like you may have a Graduated Neutral Density filter(GND). They indeed are darker in one half and you would use them just as your "techie" told you to. GND filters also have a rotating section just like Polarizing filters. AND most filters are "Circular" (round) if they screw into the front of your lens. So maybe you have a circular GND filter. (Cokin makes square GND filters that go into holders attached to your lens.)

Can you see that one half is darker than the other? If not, then you probably have a CPL, but just haven't had the right conditions to really see the effect.

What exactly is written on your filter?

[RCrosby]

Jon and Mike,
I'm a little slow on the uptake, but thanks to your advice and patience, I'm finally on the right track.
Filter is "clearly" a polarizing one, marked "PL CIR" on the outer ring.
This morning, with bright sun on the water, I was able to identify the darkening and lightening of the image as I rotated the filter.
Wouldn't have killed them to mark it in some way, but now that I can see what I was looking for, I can do that easily enough for myself.
Thanks gentlemen,
Greatly appreciated,
Rob:D