Filters fit over the front of your lens to provide control of colour or special effects.

 

They might do something simple like reduce light or glare.  They can be used to add or remove colour.  They can be used for weird effects like creating kaleidoscopic images.

 

 

 The first filter you might want to get is called a "UV" or "Skylight".  This cuts down ultra-violet glare from sunlight.  While the effect is minimal many photographers keep them permanently on their lens to provide a measure of protection.   Much better to scratch a £20 filter than an £800 lens.

 

Other photographers will tell you this is madness; that you are reducing the quality of your £800 lens to that of a £20 filter.  Personally I always keep a UV filter on my lenses and this has saved me serious damage to a lens.

 

A polarising filter works like Polaroid sunglasses.  It cuts down some light and reduces reflections.  It is normally used to darken down skies, reducing them from white to blue.

 

You need a rotating polarising filter.  This is because the effect of the polariser is dependent upon the angle of the light at the filter.   The effect is strongest when light comes over your shoulder to one side.  It is non-existent when shooting into the light.

 

To use a polariser look at the scene through the viewfinder.  Rotate the polarising lens until the effect is at its strongest.  Take the picture.   You need to do this every time; a change of angle will completely change the effect.  On some lens focussing or zooming the lens will also rotate the filter.

 

A neutral density (ND) filter just cuts down the light.  Now that might seem a little odd, when often there is not enough light around.  But if you want to get a slower shutter speed - for example shooting "milky" waterfalls - then the neutral density filter will help you.   They are described by how many stops of light they reduce.  They are often stackable, so you can use several in combination to really cut out light.

There are also colour graduated filters.  For example, a deep blue at top fading to clear.  Again this is used for giving blue skies.  Another common version is the tobacco filter that gives lovely warm sunset tones in the sky.

A handy and quite cheap way of getting a close-up focus when your lens does not normally support it.  If you are serious about close-up you really need a proper lens as the quality of most close-up filters is not great.   But handy if you only have an occasional use for it.

Filtering for colour breaks down into two types:

 

In old-school film days you could not change the colour balance of your film, so if you were shooting in artificial light you would use a filter to compensate.  Now your camera does it for you and corrective filters are not used that much.

 

When filtering for affect you are typically looking to warm-up or cool-down an image.  So a warm, orange or cool, blue filter is used.

 

Many of these filters are no longer used, because the effect can be easily reproduced in software on your computer.  This means you do not need to commit to a particular treatment until later.

 

If you shoot in RAW mode then you have a huge range of filtering options that are very effective.  A RAW file contains extra information that you do not normally see.  But using software filters you can bring that information back into your image.

 

For example you can add neutral density and colour correction filters afterwards.

 

 If you shoot JPEG then your range is slightly limited because a JPEG files does not contain quite the same level of extra information.  Nevertheless nearly all the same options and flexibility are open to you.

There are a few filters that cannot be easily reproduced in software.  The polarising filter is the main one.  You cannot use software filters to reduce reflections, glare or put natural colour back into skies.

 

The ND and ND-Grad filters change what the camera records.  Although you have some leeway with brightness in software an ND filter might be the only way to get the original base image.

 

 Star burst filters are one of the few special effects filters I've never seen well done in software.

 

 Beyond that there are more filters, both sensible and bonkers available in software than you can ever imagine.