Tuesday, January 3, 2012

Circular Polarizer: Miracle Maker

Circular polarizers are a very interesting piece of equipment and usually overlooked by beginners who only buy UV filters as per the sales person's advice. I like to say that the polarizers are magic makers, the very first time you use one, you will be astonished with what it can do. Hit the jump to learn more.


The polarizer filter idea is the same as your sun glasses, I don't want to get into scientific details about light waves, polarization and stuff, but if you're interested, you'll find a good explanation here. Suffice to say, a polarizing filter cancels a part of the light reflected from any object, be it the sky, a car's windshield or the water's surface.


So how can this be of benefit for you? I'll give you a small exercise, go outside in the morning and try shooting your car from outside and see the car's interior through the glass, mostly (depending on your angle) you'll find that the glass reflects the sky and the surroundings. Check this example:

Now here's the same picture with the circular polarizer:

Just like magic, but the sharp reader will notice that the side windows have become reflective in the second picture, you can't have everything when there are different angles from which the light is reflected. But if I had to have them all clear, I would use a tripod, take two shots and use photoshop to merge the parts I needed.

Polarizers are generally useful in eliminating reflections like the example above, more examples would be shooting wrist watches, shooting fish through tanks, shooting through the surface of the water, etc...

They can also be used to get better contrasting skies and miraculously vibrant images, this works better when you're shooting 90 degrees to the sun (i.e. the sun is either to your left or your right), and since the polarizing effect depends on the angle of reflection, you'll usually find that the sky color doesn't become even across the picture. The picture below is a standard picture shot without the polarizer.

And here's the same picture with the polarizing filter:

Unbelievable! So how do one use a polarizer? See the picture at the top of the post? This is how it looks like, you thread it to your lens like any other filter and you have a part at the front that rotates, and you keep rotating the filter while looking through the viewfinder until you get the look you want. It will also be very good if your lens' front element doesn't rotate with focusing since this will change the filter's rotation each time the camera changes focus.

They always tell you to buy the best brands in filters since they have coatings that minimizes reflections and will not degrade the picture in terms of sharpness, however, polarizers are very expensive especially if you have a large diameter thread, and different lenses with different thread sizes. I myself went for a not-so-expensive 72mm (larget lens thread size I own) Chinese brand since I don't use it a lot, and I didn't find it cost me pixel sharpness at all, and for my remaining lenses I bought some cheap Bower step-down adapters like the one below.