Before we start, a tiny word of warning. There are cheap filters and expensive ones.
The latter are precision made from high quality optical glass and multi-coated to
reduce flare, the cheap ones just aren't. Using a low quality filter in front of
a high quality lens can have a slightly detrimental effect.
Like all quality issues, this is entirely a matter of personal taste. Photographers
working on a tight budget should not be put off using the cheaper filters, because
their practical benefits could easily outweigh the slight drop in quality.
Sometimes, there is just too much light. Not often in the UK, you might think. But
even here, if you want to use a very slow shutter speed or wide aperture, it can
give you more scope to reduce the amount of light coming through the lens.
Close up lenses
If you don't have a macro facility built in, you can still do close up work by fitting
a close up lens to your filter ring. The quality of these does vary tremendously
and you tend to get what you pay for.
Skylight and UV filters
Ultra violet (UV) filters are designed to cut down the slight blue haze that can
appear on shots taken from some distance away. Whilst it is possible to improve on
this in editing, it's not so easy to remove the haze if only part of your picture
shows anything in the distance. Skylight filters do the same job but add a slight
pink hue to your image to enhance the effect. This is less useful to the digital
Some photographers fit these types of filters simply to protect the front element
of their lens. This is something that hasn't changed with the advent of digital cameras.
With the caveat of putting cheap filters on expensive lenses, this is still a worthwhile
In practice, these have different effects in different situations but in essence,
what these filters do is to block polarized light.
So, what is polarized light? Well, it turns out that as light moves forward in straight
lines, it also vibrates a little from side to side. Normally, this vibration happens
at any and all angles perpendicular to the direction of travel. However, when light
bounces off certain materials at specific angles, the vibration only occurs in one
direction. This is polarized light.
If the theory doesn't make much sense to you don't worry, this is how you use a polarizing
filter in practice. All polarizing filters have two rings, one which fits securely
to your camera and a second that holds the filter itself and can be freely rotated
through 360 degrees. In use, you frame up the shot then rotate the filter until the
desired result is at its maximum. If you move the camera, you may have to reset the
angle of the filter. I you turn the camera from landscape to portrait, you will definitely
need to turn the filter to compensate.
Photographically, there are three effects you can achieve with one of these. Neither
of which are easy (or sometimes even possible) in editing. It can darken a blue sky,
reduce reflections from glass, water and other materials and reduce glare or shine
from some things. In all these uses, there are "critical angles" where the effect
is at its maximum.
Some of the the light from a blue patch of sky is polarized and the critical angle
here is 90 degrees from the sun. It doesn't work on clouds and it doesn't work when
either facing or looking directly away from the sun. But, if you shoot at 90 degrees
to the sun, you can transform an ordinary sky into something tropical with a polarizing
Reflections from glass or water are polarized at just over 50 degrees. This means
that it's usually quite easy to remove reflections from the water's surface when
you are looking down on it at this sort of angle. If you stand square on to a piece
of glass or look straight down into water, then a polarizing filter will have very
little effect on your reflection. You need to shoot through the glass at an angle
of around the 50 degree mark to get the greatest benefit from the filter.
The laminated safety glass used on automobiles can sometimes reveal a blotchy appearance
when shot with a polarising filter. This is because it's constructed as a thin film
squeezed between two pieces of glass. The polarizing filter reveals microscopic variations
in the film. Scientists use this to take measurements of such things under laboratory
A polarizing filter will have no effect whatsoever on reflections from metal surfaces.
This includes mirrors because it's the metal coating on the back that does the reflecting,
not the glass. However, there are many non-metallic materials that are semi-reflecting
or at least shiny. Most paints and varnishes come in to this category.
The "shininess" of many things in the real world can contain at least some polarized
light so it might be possible to reduce that with a filter. This is much less predictable
simply because most things in the real world are not flat like a piece of glass.
Only reflections at or near the critical 50 degree angle will be affected. So you
really can't tell what the effect will be until you try it. Sometimes, there may
be no effect whatsoever but, other times, you may be able to reveal colour and detail
that would otherwise be masked by the shiny appearance of the object.
Because the polarizing effect is purely optical, you can always see it for yourself
by simply looking through the filter and rotating it. It might be easier to find
the best position and angle for your camera before fitting the filter.
Linear or circular
If you go looking for a polarizing filter, the first thing you will discover is that
they can be either linear or circular. First of all, they both perform exactly the
same function and work exactly the same way. The first polarizing filters were linear
but it was soon discovered that they could interfere with the working of auto focus
and auto exposure systems. The circular one cures this problem and this is the type
you need for all digital cameras.
If you would like to try our some of the filters described above, without breaking
the bank, why not take a look at the extensive range of types and sizes of lens filters
from 7 day shop.
Go to filters