A Beginners Guide to Filter Systems

What filters to use and what are the best filters to start with is a common question raised by club members. This article is intended to give a simple overview of what filters are, what types are available and which filters are the ones to consider getting first.

So what is a filter and why should we consider using them.

Well to put it simply, a filter is a small plate of glass or resin placed in front of the camera lens with the objective of altering (and hopefully improving) the image being taken. The problem is that there are several different filter systems and thousands of filters available for each system. So where do we start?

There are two filter systems in general use, the circular screw-on filter and the rectangular or square filter.

Screw-on Filters – These comprise of a metal ring with a screw thread to screw onto the lens and a thread on the other side to allow you to ‘stack’ filters.

The ring holds a thin glass plate which is coated or shaped to provide the filter effect.

They come in a variety of sizes to fit different lens sizes.

The most commonly used of these filters by far is the Skylight or UV filter.

Now despite what I said earlier, the UV filter does very little to change the image being taken but are used to protect the front of the lens from scratches. Most people who use them, buy a filter for each lens and leave it on all the time.

However, not everyone likes using them and you do have to be careful. The glass in the filter is very thin and fragile and even a small knock in the wrong place can break the glass. You will then be faced with sharp broken glass all over the front of your lens, not ideal!

The main upside of screw in filters is that they are (generally) very light and because they are almost always made of glass, the optical quality is usually very good, even at the cheaper end of the market.

The downsides are that you have to have a filter set for each lens size that you have, which can quickly translate into hundreds of filters, and they can be very fiddly to change.

Rectangular or Square Filters – These comprise of an adaptor ring which screws onto the front of your lens, a filter holder which attaches to the adaptor ring and a range of filters that slide into the holder. Most systems will allow you to stack at least 3 filters onto a holder.

The main advantage of this system is that you only have to buy an adaptor ring for each of your lenses, which are relatively cheap, then you can use the holder and all your filters with all your lenses. They are also a lot less fiddly to change than the screw-in filters.

This system comes in a few different sizes to cope with different ranges of lenses. The most common is probably the 85mm system (also called P system), which is fine for lenses no wider than 28mm and a max lens diameter of 82mm. For wider angle or bigger diameter lenses, you will have to go to a 100mm system. Note that filters are NOT interchangeable between the filter holder sizes. However, at a push, you can just hold a filter in front of the lens!

Filter Types

OK, so what filters should you start with?

To some extent this depends on the kind of photography you like to do. Generally, the most useful filters apply to landscape photography, so I’ll concentrate on that use.

Polarising Filter – This is very useful if you are taking photographs by water, such as seascapes or lakes. It will have the effect of reducing reflections off the water or other reflective surfaces. It will also increase the colour saturation, particularly in the sky, so that blue sky will become more pronounced. You can increase/decrease the intensity of these filters (usually one polarising plate rotating against another) but be careful not to overdo the effect, otherwise you can get colours that start to look false and even some colour banding in the image. An excellent filter to add early on to your set.

Neutral Density Graduated Filters –  These filters are coloured with a neutral colour at one side of the filter that gradually fades to nothing half way across the filter. They come in a variety of strengths and a starter set will usually comprise of three filters plus the holder. These filters are used when you have a bright sky and dark foreground. In these conditions, the camera can’t cope with the light differential and you either end up with a washed-out sky or a foreground that is too dark. These filters bring the level of light from the sky down to the dynamic range of the camera and allow the detail of the sky as well as the detail of the foreground to show.

Neutral Density Filters – These are similar to ND Grads above, but are coloured across the whole filter. You use these filters when you want to reduce the overall light entering the camera, for example, if you want to use a slow shutter speed to blur flowing water but the light level is too high to allow it, ND filters allow you to increase the exposure times. These are available up to extreme levels with ‘Big Stopper’ ND filters giving 10 stops of light reduction which (for example) will extend an exposure of 1/125th sec to 8 secs.

What brands to choose

This is very much down to personal preference and how much you want to spend.

At the budget end SRB Photographic have a good range of their own brand screw in and rectangular filter systems.

For screw-in filters, Hoya are generally recognised to be good quality at an affordable price.

Cokin filers have been the favourite starter for square format P filters for a long time and are a good entry level choice.

At the top end, Lee filters are usually considered to be ‘professional’ standard filter systems, but Format Hi-Tec are also extremely good quality and slightly cheaper.

As always, shop around to see what suits you.

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