I'm using this currently on my Canon 50mm f1.4 lens for day time shots and to reduce unnecessary glare aside from better saturated colors if not add some warmth.

Construction is great, solid, no distortion looking at the filter and the 58mm fits perfectly on my f1.4 lens.  Like any filter you'll find the lens cap won't be a solid fit as the thread on the opposite end isn't as tall.  But the cap will stay there but just be sure to watch for any bumps that may cause it to come off.

The range which it cuts the glare on glass, windows, water and any reflective surface is great.  The sky can look washed out all the way to saturated darker blue color with clouds popping out while depending on the orientation you can add a cool or warmer feel to the photos.

I've used Heliopan and B+W so compared to the pro-grade filter, you'll probably find that this polarizer isn't the best out there but for the price it does what it's supposed to.  When I had B+W 77mm multi-coated CPL ($150 here) on my Canon 70-200mm lens, the sky really popped with dark saturated blue skies and the control was better.

Overall it's a great polarizer.  Unless you absolutely need more saturated colors and reduce glare to the maxium then go with the more expensive multi-coated filters.  I would say this Tiffen filter is a standard for circular polarizer and won't disappoint.  Plus it protects your lens like any UV or other filters used.  I'd rather smash a $20 filter versus a $400 lens.

Circular polarizer does make daytime shots more fun and less correction post processing.  And sometimes you can't control everything you shoot with so a filter becomes a must in some cases.  With a lens that can be as wide as f1.2-f1.8 sometimes putting the ISO level 100 doesn't always allow you to shoot at the widest aperture.  In a sense it does act like a neutral density filter to a degree while cutting glare and allowing you to shoot a fast moving subject or freeze the moment.
I'm using this currently on my Canon 50mm f1. 4 lens for day time shots and to reduce unnecessary glare aside from better saturated colors if not add some warmth. Construction is great, solid, no distortion looking at the filter and the 58mm fits perfectly on my f1. 4 lens. Like any filter you'll find the lens cap won't be a solid fit as the thread on the opposite end isn't as tall. But the cap will stay there but just be sure to watch for any bumps that may cause it to come off. The range which it cuts the glare on glass, windows, water and any reflective surface is great. The sky can look washed out all the way to saturated darker blue color with clouds popping out while depending on the orientation you can add a cool or warmer feel to the photos. I've used Heliopan and B+W so compared to the pro-grade filter, you'll probably find that this polarizer isn't the best out there but for the price it does what it's supposed to. When I had B+W 77mm multi-coated CPL ($150 here) on my Canon 70-200mm lens, the sky really popped with dark saturated blue skies and the control was better. Overall it's a great polarizer. Unless you absolutely need more saturated colors and reduce glare to the maxium then go with the more expensive multi-coated filters. I would say this Tiffen filter is a standard for circular polarizer and won't disappoint. Plus it protects your lens like any UV or other filters used. I'd rather smash a $20 filter versus a $400 lens. Circular polarizer does make daytime shots more fun and less correction post processing. And sometimes you can't control everything you shoot with so a filter becomes a must in some cases. With a lens that can be as wide as f1. 2-f1. 8 sometimes putting the ISO level 100 doesn't always allow you to shoot at the widest aperture. In a sense it does act like a neutral density filter to a degree while cutting glare and allowing you to shoot a fast moving subject or freeze the moment.