How to Use a Polarizer
Polarizers are some of the most helpful tools in photography, and they are very easy to use. Just put the filter on the front of your lens and rotate until the picture looks good. This super-super-quick guide will teach you all the basics of polarizing filters. To start, polarizers do three main things for your photo:
1) Darken skies
2) Saturate leaves
3) Reduce glare
(Also, you can use a polarizing filter to make rainbows pop.)
In terms of darkening skies, polarizing filters are the best tool a photographer can have. In photos where your sky blown out to completely white, polarizing filters can darken it back to a blue color. Note that polarizing filters are not as useful when they point directly towards or away from the sun, simply because of how the atmosphere reflects polarized light. Below is a good example where I used a polarizing filter to darken the sky.
Another useful reason for a polarizing filter is to saturate colors, especially leaves and grass. This is because a polarizing filter cuts glare that otherwise reflects off of plants, making them seem dull.
Lastly, polarizing filters help reduce glare in your photos. This glare can be from almost anything: water, windows, and anything in between. The only reflections that polarizing filters cannot reduce are those glinting off of metal. In the photo below, the rocks would be annoyingly shiny if I had not used a polarizing filter to cut glare.
Remember, as with all filters, subtlety is key. If someone can tell that you used a polarizer, you probably messed up.
In terms of recommendations, I always use the B+W Kaesemann polarizing filters. They are expensive, but they are also waterproof and shock-proof. Thirty seconds before I took the photo above, I dropped my filter into the river. Not only did it hit rocks when it landed, but it took about a minute to find in the raging water. Afterwards, I dried it off and slapped it back on my camera for the photo you see above. It didn't have a scratch.
Also, as a final word of advice, make sure not to use a polarizer on a super-wide-angle lens pointed at the sky. Why? As I said above, a polarizer doesn't darken the sky much around the sun. So if you use a super wide lens, you could end up taking a picture where only part of the sky is dark, which looks bad.
That's about it! Thanks for reading, and I hope this helped.