Lens Filters Buying Guide

by Giles Babbidge 3 October 2013

Filters are curious things. So simple in their design and yet to the uninitiated they can be the cause of much confusion - both at the time of purchase and when put into use.

Very often, enthusiastic photographers readily part with their hard-earned cash, purchasing filters which they believe will improve their pictures, only to be disappointed with the results. This actually isn’t anyone’s fault, rather a matter of education; as ever, knowing how to pick the right tool for the job and, more importantly, knowing how to get the best out of it, should be your starting point.

In this guide, I’m going to give you a basic overview of what’s out there. Of course, not all shapes and varieties of filter will suit every photographer (or their budget), but there will be something that's right for you. With a little thought and pre-purchase research, you can be sure that you’ll be spending your money wisely when the time comes to invest in a set of filters.

What is a filter?

Simply put, a filter is a piece of glass or resin which is (usually) placed in front of your camera’s lens. Some are more elaborate than others in their function, but all share the quality that they change how your pictures will look at the time of exposure (and, in most cases, beforehand through the viewfinder, too). Some filters, for example ultraviolet types, don’t really have a marked visual effect, while others can be quite dramatic, either in cutting out a lot of the light entering the lens or introducing colour and/or contrast to the scene in front of your camera.

So what are filters used for? Well, there are two main reasons why photographers use them - lens protection and creativity. In the case of the former, many people choose to leave a clear threaded filter attached to the front of each of their lenses from the word go. The argument for doing this is that, should the front of your lens get knocked, scratched or otherwise unfortunately damaged, there’s a fair chance the filter will take the brunt of the impact. With lens repair costs enough to send a chill down the photographer's spine, the cost of merely replacing a damaged filter is understandably very attractive when you put things into perspective.

On the flip side, some people maintain that image sharpness is compromised by the use of these filters. While this may certainly have been true in the past, especially with cheap filters, the quality of materials used these days is so good that the average person would probably be unable to tell the difference in the resulting pictures. At the end of the day it’s your choice but, having had lenses saved by protective filters myself, I know what I’d rather do!

When it comes to creativity, the possibilities are limited only by your imagination. Filters can be used singularly or ‘stacked’ in front of the lens - it really depends on what visual effect you want to achieve. It might be that you want to cut out reflections in glass surfaces or perhaps you want to tone-down a bright white sky - either way, there's an exhaustive number of combinations available to the photographer.

How is a filter attached to the camera?

There are several main designs but, regardless of the way they attach, all varieties of filter essentially work in the same way once firmly held in place. Perhaps the easiest design to use is the round, screw-in filter (note: this is not the same as a circular filter, which I'll come on to later), which just screws into the filter thread on your lens. When making your choice, be sure to double-check the thread size of your lens (often clearly marked in millimeters - such as 67mm or 72mm - on the lens itself or on the underside of the lens cap) as this is the key bit of information needed for correctly matching both components.

Screw-in filters are arguably quicker to use, depending on your scenario, so if you are a photographer who is always on the go (such as at public events), they might provide the best option. They also don’t suffer the risk, as with slot-in filters, of slipping or sliding out of a holder if you happen to be changing position in a hurry.

The other route you could take, then, would be to use slot-in filters, which by their nature require you to use a dedicated holder (which can usually hold several filters at a time, if you so wish). For this, you’ll also need to purchase an adapter ring which attaches to the front of the lens in use, onto which the holder then slides. The holders and adapter rings themselves vary depending on manufacturer and individual product specifics, but so long as you stick with the same ‘system’ you’ll be absolutely fine.

Types of filter

As you might imagine, there are hundreds of creative filters available. These span every conceivable effect from colourful light correction to starbursts, soft focus and even aids to focusing. The following list covers the most popular choices, with a brief overview of what each can do for you.

Protective

As the name suggests, these threaded filters are designed to protect the front element of your lens from all manner of scrapes, as well as from dust, dirt, moisture and fingerprints. Because they are essentially just clear glass, they don’t have any discernible effect on the amount of light entering the lens (and therefore they don’t affect exposure time).

The rule of thumb here should be, as ever, buy the best that you can afford. Remember, the light will have to pass through the filter before travelling through the lens and onto the camera sensor, so the higher the quality of that glass, the better. Realistically, this equates to ensuring you get the sharpest pictures possible.

Ultraviolet (UV) and skylight

Before the days of dedicated 'protective' filters, threaded UV and skylight filters were popular choices for protecting lenses. Just as with protectors, they allow light to pass through almost uninterrupted. Aside from this, their main purpose is to cut out excessive ultraviolet light and haze, thus improving colour and contrast in your pictures.

A word of warning: if you happen to be heading off to photograph an epic waterfall such as Niagara Falls, do not use one of these filters. Many a time a photographer has come back from their day trip wondering just why the beautiful hazy rainbow they saw hasn’t been captured by their camera. Clearly, their filter did what it was designed to do, which is to cut through the mix of sunlight and moisture hanging in the air. If lens protection is what you’re after, go with a protector filter instead.

Polariser 

Polarising filters are something of the golden child in the filter world because they are just so very useful. This is why a lot of people maintain that every photographer should have one in his/her bag.

By far and away the most popular use for them is to reduce (or completely remove) glare and reflections on reflective surfaces, as well as to darken blue skies and bump up the saturation and colours in a scene. For this reason, they are especially popular with photographers who regularly capture images of bright, shiny subjects (such as cars) and vivid landscapes. With the latter, a polariser will particularly make the clouds stand out against a rich sky, adding a sense of atmosphere and drama, with the blue of the sky and green of the land showing up particularly well.

Polarisers come in circular and linear types. With the filter in place, simply turn it one way or the other through 360 degrees; you will see the visual effect changing through the camera’s viewfinder, especially when the camera is positioned at a 90 degree angle to the sun (which is the most effective shooting position). In this way, you have complete control over just how pronounced the effect is, although bear in mind that you will lose two EV stops of light because the filter absorbs light in the process - so keep an eye on your shutter speed in order to prevent camera shake. Linear polarisers can confuse the AF and metering systems on modern DSLRs so, unless you're using an older analogue model, it's best to stick with circular polarisers for general use.

Neutral Density (ND)

Neutral Density filters are also regularly to be found on the serious landscape photographer’s kit list. Rather than having an immediately visible effect on the picture, the power of NDs can be seen on both the camera settings before the shutter is released and, of course, in the final images.

Simply put, the purpose of these filters is to reduce the amount of light entering the lens (and so hitting the camera’s sensor). Why would you want to do this? Well, there are times when a slow shutter speed or large aperture is required, but the conditions are too bright for the camera to accommodate them. For example, imagine you want to record the movement of a waterfall; for this, you’ll most likely want to capture the fast-flowing water as an artistic blur, rather than in pin-sharp detail. By cutting out overall brightness, the ND filter allows you to use a much slower shutter speed than would normally be permissible at a given aperture.

Back in the days of film photography, you had to make the choice of whether to load black and white or colour film into your camera. On the basis that black and white was your preference, there was one set of filters in particular which would surely be in your kit bag.

Comprising of red, orange, yellow and green, these sets are still available to assist photographers who see the world in black and white (converting their colour digital files at the editing stage). These offer a variation of effects to suit different situations and personal preferences. Red and orange filters are great for bringing out clouds in skies, while yellow and green filters are more subtle in what they do, making them perfectly suited to more gentle tones and textures. The latter two also work well for portraits, having a really nice smoothing effect on your subject’s skin, so they're good if you want to cover up small blemishes.

As well as the above, film users might also like to think about purchasing what’s known as a black and white viewing filter, which allows you to see contrast, tone, highlight and shadow densities within your pictures before releasing the shutter.

White Balance Filters

Colour casts are often a source of great frustration in a wide variety of situations and variable lighting arrangements. Whether you’re shooting in the studio, an office space, your living room or outdoors, a myriad of light sources can present their own warm or cold casts which have to be corrected either at the time or later on in post-production.

Rather than relying upon computer software, adjusting your camera’s white balance is, of course, what you need to do as a first step. By using the Custom white balance setting along with this filter, you can be more confident of capturing accurate colour right from the moment you prepare to take your pictures.

White balance filters are available in a range of thread sizes specific to the lens in use and are simple to use: simply place them over the front of your lens and take a reading. This is then stored in-camera to provide a constant white balance reference for all subsequent images.

Close-up (set)