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Polarising Filter
27/12/2011 - 21:37:48 - 0 comments - By D47
Recently I acquired a polarising filter for my camera. I'd never used one before and I didn't really know what they were actually for, something to do with reflections I guessed.

After playing with it for a while and reading a lot of things on-line I think I get the basic idea, there is so much science involved in the technical details that it seems impossible to implement it all into a single piece of glass.

A polarising filter allows you to cut varying amounts of sunlight reflected off of non-metallic objects depending on the conditions of the shot.

The biggest factor that effects how your photo will look with a polarising filter is the rotation angle of it on your lens. At different rotations the filter will only allow light oriented in that direction. How light can be oriented in a particular direction is a hard one to imagine. If you think of light as a wave with an amplitude and wavelength then imagine the filter as a group of slits that only let the wave pass if it fits through the slit. For example, a wave that is oscillating up and down vertically will not fit through a flat horizontal slit.

Anyway you don't need to be a physicist to be able to use a polarising filter. The end effect of rotating the filter is that you can selectively accept only certain groups of light through to the camera. If you watch through your viewfinder you can see what effect it is having and take the photo when it looks the best.

The goal of course is get the picture you want and the best way to make use of a polarising filter is to know what kinds of effects it can achieve.

Another factor that determines how the polarising filter will affect your photo is the angle of the reflected light. I've read somewhere that you need to be at 50 degrees for it to be completely eliminated. I don't know why this is nor do I know where to go to find out but it does have an effect.

If you look through your filter at an LCD screen you can get a feel for what angles and rotations give the best results. LCD screens produce polarised light and so they can be blocked using a polarising filter.

The following images demonstrate how a polarising filter can be used to remove reflections from your shot. (Click to expand)

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No photoshoping or other manipulating was performed on these images (except for resizing). The photos were taken with the same camera settings within seconds of each other. They represent the actual difference when using a polarising filter.

Anyway I love the effect of these filters and I will definitely use it regularly.
 
 
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