Which Filter to buy for your lens.

Put filter into the Ebay search and narrow down to photographic and you come up with hundreds of offers. Buying secondhand can save you quite a bit, but what do you buy and why?

A filter usually has the practical advantage of protecting the front element of your lens from dirt and scratches, plus it is easily replaced if damaged. Many filters in the past were designed to help film cameras record balanced images in different lighting conditions, either warming up or cooling down the final effect. Back in the days of Black and White colour filters were used to eventuate contrast. These days of Digital Cameras, most have programms set to compensate for differing conditions, or the image can berectified on the PC later. So a filter has two uses, protection and image manipulation.

WHAT DO YOU NEED TO KNOW TO BUY A FILTER

1. Filter size (shown in mm and often marked on the front of the lens), this refers to the diameter of the filter required ie. Standard Canon lenses are usually 52mm and most Canon L series lenses are 77mm, but there can be 58mm, 62mm, 72mm etc.

2. Single thread or double thread. Most are double threaded meaning you can stack additional filters on the front.

3. Rim size. If you are using wide angle lenses the narrower the filter the better as it is less likely to cause vignetting (there is usually a premium on the cost)

4. The Effect you require (examples later)

5. Coating. Unless you are buying the cheapest of filters most now available have a surface coating designed to both cut down glare/flare and to improve light transmission into the lens. The number of coatings and whether on one side or both sides of the filter usually improves its performance but adds to the cost.

SO WHICH TYPE FILTER TO BUY?

Basically you need a UV filter for general lens protection, anything else will add a slight colour effect. Look for UV0 or UVN. Skylight filters usually have a slightly warming effect.

Next a Polarising Filter is very useful. Choose a Circular Polarizer (CPL) over Linear Polarizer (The former allows your auto focusing to work without hindrance). This filter when rotated can be used to reduce reflections from shiny surfaces, water, glass, metals, gloss paint surfaces etc. Also when used out of doors it will increase the density of colours especially blue skies, sea etc.

Effects filters. Most filter effects can be added after on you PC if you shoot in digital, but if you still want effects filters go for the square gelatine filters which fit an adaptable holder such as Cokin or Lee. This system can be used on all of your lenses with the adapter ring, plus they are easily stored. Consider the Professional range ( Cokin P ) if you anticipate using with lenses that take larger filters otherwise Cokin A.

WHICH BRAND IS BEST?

I tend to favor Hoya as they usually offer good value and performance

Hoya produce a range of filters but look out for HMC in the discription (Hoya Multi Coated) and if you need a narrow rim filter look for Super HMC

B W Filters made in Germany are also excelent along with Sigma, Canon and Nikon filters