Choosing the right filter for your photography
You can use a variety of filters to improve your photographs, it's just a question of understanding which ones are appropriate. Here are some useful tips to get you started.
What Will I Be Photographing?
Choose the right filter for the job:
UV or skylight filters - can be used at any time to protect your lens
graduated filters are used to make skies look more dramatic and to balance the exposure when the sky is much brighter than the foreground
polarising filters can be used in two ways: to improve colours in your landscape shots on bright days and to prevent reflections on shiny surfaces and water (and they can be used like ND filters, below) - don't be tempted to use polarising filters when photographing wildlife, because they will slow down your shutter speed and you may not be able to freeze fast action
ND filters are used when you need to shoot at a very slow shutter speed to create blurring, e.g. waterfalls
magnifying filters can be added to a standard lens for extra magnification when doing close-up photography
UV or Skylight Filters
These are protective filters that screw onto your lens. They don't affect the image at all. If you are working somewhere very dirty or where you have to put your lens directly onto something (like wire if you're photographing at the zoo) they will protect it. Somehow dust does find its way between the filter and the lens and can detract from your photos, so you may prefer just to use your lens hood instead.
At the cheaper end, you can buy a set of graduated filters for about £30. They fit in a filter holder, but you can handhold them in front of your lens, provided your camera is set up on a tripod.
At the other end of the scale, you can buy Cokin or Lee filters, which could cost you £200 for a set. The advantage of the most expensive filters is they they are taller than the cheaper ones, which gives you more scope for adjustment, and they are made of better quality materials so are less likely to scratch. However if you're not a dedicated landscape photographer you might prefer to use cheaper ones at first, then replace them if they do get damaged.
You can buy filter holders for all the above, then you buy an adapter to make the holder fit your lens, so that you don't have to handhold the filter in front of the lens.
The filters come in ND2 - very pale grey, ND4 - medium, and ND8 - dark grey. You can of course put one on top of another to create the effect you want.
Set up your camera for your landscape shot without the filter, then put the filter in place and adjust the position until you get the desired result. If you find that using the filter makes the exposure for the foreground of your shot change, you may prefer to work in Manual mode to lock the exposure.
Polarising filters come in two types:
Circular screw-on – they fit directly on the end of your lensRectangular – for filter holders
On bright days a polarising filter can improve colours and detail in skies and help to saturate colours throughout the image, but only when the sun is at 90 degrees to the camera. Be aware that because they darken the image they also cause a slower shutter speed. They can also be used to cut through reflections on water so you can photograph rock pools for example.
ND Filters simply darken the whole scene, forcing your camera to use longer shutter speeds than for the same scene without filters, so are good for adding blurring when photographing waterfalls for example. Like graduated filters, they vary from ND2 to ND8. On very bright days you may need more than one to give you a long enough shutter speed for your flowing water shots.
Magnifying or Close-up Filters
These screw on to the end of your standard lens to increase magnification. The image quality may not be as good as with a dedicated macro lens, but they are a relatively cheap way of getting started in macro photography, at around £40 each.
Coloured filters used to be used by film photographers to add colour to their images, for example to make them feel warmer or colder, but this can now be easily achieved either with the camera, by adjusting the White Balance, or on the computer, so they're not often used.