Keen amateur photographers and professionals have often turned to the use of a filter to alter or enhance a scene in some way. I say “have” because along with the advent of digital photography there also came digital image processing, and with it a myriad of tools that can negate the need of a filter. However! . . .

Filter types
Photographic filters come in two basic formats, i.e. the threaded and square varieties. The latter became hugely popular when marketed by the Frenchman Jean Coquin – of Cokin filter fame – in the late 1970’s.

Given these two filter formats, we’ll evaluate their advantages and disadvantages before going on to cover a few of the many types of filters that abound.

The threaded filters are long established and are arguably better quality than their square counterparts, as they utilize glass, and not an ‘organic glass’ known as CR-39 polymer which is used for square filter production. Latest score: Threaded filters 1  Square filters 0

The drawback with threaded filters is if you own two or more lenses, it’s likely that the diameter of the filter thread on the leading edge of each lens will be different. This differing filter thread size means that you will have to buy a full set of filters for each lens you own, and this can get rather expensive! The square filter on the other hand has the advantage of being used on all of your lenses regardless of the thread size. This is achieved via interchangeable threaded adapters that snap into a universal mount onto which your square filter slides. You only need one adapter ring for each thread size needed, with the cost of the adapters being considerably less than buying several filter sets. Score update: Threaded filters 1  Square filters 1

The threaded filter manufacturers used to claim that the use of glass provided better quality than the organic glass type filters, but in recent years some of them have turned to manufacturing square filter systems too! Score update: Threaded filters 1  Square filters 2

Filter basics
O.K., so now down to filter basics . . . a few of them anyway. A good rule of thumb is if the filter you are using doesn’t improve the image, then don’t use it! That’s my main criteria for filter use in a nutshell.

Most of you will have been advised at some point to leave the ultra violet (UV) or skylight filter on your lens at all times so as to protect the front lens element against hard knocks. “Better to lose the filter than your expensive lens”, they say. I’m sure that has proved to be good advice for a few, but for the majority it’s just another expense. In case you’re wondering, both of these filters filter out ultra violet haze, especially in the mountains. So does a polarizer.

Sure, it can be said that we can get similar effects via digital processing of an image, but putting that aside for now these are the filters I recommend most for general color photography . . .

Polarizer: It will darken blue skies without affecting the foreground colors other than a little saturation. It also reduces
or eliminates reflections on water and glass, and reduces haze. If you have polarized sunglasses you’ll be able to observe the same effect. A polarizer works best when the sun is at a 45 degree angle to the way you’re facing, but also works, albeit to a lesser degree, from other angles too.

Grand Teton national park, Wyoming: Hazy day, no filter

Moments later, but this time with a polarizing filter attached.

Neutral density: Use to lengthen exposures for dreamy effects such as ‘soft’ water, ‘streaking’ clouds and suchlike. The denser [darker] the filter, the better. Variable neutral density filters are a fairly new technology, but have the added advantage of what could be termed as multiple ND filters packed into one filter.

Graduated gray/Split neutral density: Use to darken bright featureless skies in landscape pictures. These filters are darker at the top fading to clear in the center to give a pleasing tone to what would probably be a blank sky. They come in all sorts of colors, pale orange is useful at sunset, but again I suggest that you keep it natural starting with gray.

County Kerry, Ireland: The graduated gray filter also covered the top of the cross, but I was able to lighten it up with software.

County Kerry, Ireland: On overcast days the sky is a dull white, and the use of a grad gray filter adds some texture and drama.

When it comes to graduated filters, square filters have an advantage over threaded in that the filter can slide up and down vertically to cover the exact area of the sky you wish to cover. This isn’t possible with threaded filters. Score update: Threaded filters 1, Square filters 3

Easy does it
Unfortunately, the tendency for most folk when they purchase a new filter is to over-use it. Sunsets and landscapes taken through red and orange filters are so garish that their lasting impact is brief. However, these same colors used in black and white photography will darken skies dramatically. Then again, one does have digital processing with which to add any effect you so wish.

I refuse to be blinded by the facts!
Even though square filters have the edge over threaded I must confess to using the latter! I have a large collection of square filters that have been napping undisturbed in the garage for a number of years, mainly because the square system polarizer – which happens to be round filter – would fall out of the holder all too frequently. My other go to filters are the neutral density and graduated/split neutral density. Final score: Threaded filters 2  Square filters 3

In conclusion, the message over and over again will always be for whatever filter you use, keep it natural!

Remember that whatever you photograph, the end result is limited only by your imagination!