The ultimate guide to FILTERS

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If you think that filters aren t important in the digital world, then think again! Read on and weshow you just what they can do...

Before the arrival of digital imaging, any self-respecting landscape photographer would carry an arsenal of filters. Aside from choosing what kind of film to shoot with, photographers usually couldndo all that much to influence the exact character of the images they shot. Relatively few photographers did their own black-and-white processing and printing, and even fewer were in a position to do so with colour film.

However, photographers could invest in photographic filters that enabled them to make crucial adjustments to the appearance of an image at the time of capture. These included polarisers, warming and cooling filters, colour-graduated filters, neutral-density-graduated filters, solid-ND filters and red-enhancing filters. Collecting and using these essential accessories was for many photographers a pleasure and skill all of its own and they soon became cherished possessions.

These days, the overwhelming majority of photographers now shoot digitally and routinely process their images using software like Lightroom and Photoshop. This has resulted in many of these filters being sold on eBay, often for a fraction of the price that they were originally purchased for.

Colour-temperature filters, such as the classic 81B and 81C warming filters, are simply no longer required when photographers have fully adjustable white balance settings at their disposal in-camera. With Adjustment Layers in Photoshop and the ability to make incredibly precise and selective adjustments in RAW conversion software, filters like a coral-graduated filter or a red-enhancing filter have largely been consigned to history. This is because the effects that they produce can be re-created quickly and with much more precision in postprocessing software.

So, are filters now a thing of the past? A quaint relic from the history of photography that we no longer need or want? Not quite. In actual fact, there are still quite a number of filters that remain extremely useful and even essential for many photographers. This is because, despite the increasing capability of digital technology and software, there are certain effects that are very hard to achieve in Photoshop-effects that a filter will make light work of.

Arguably the most basic of all filters are UV filters. These were used, as their name suggests, to limit the amount of ultraviolet light that could find its way to the film, as this could result in a somewhat hazy effect. This isna problem with digital sensors, as they are not affected by ultraviolet light like this.

As UV filters are fairly cheap to purchase and donproduce a particular effect as such, theyremained in use as protective accessories. Photographers simply attach a UV filter to their lens and then leave it there as a means of avoiding damage to the front element, which is vastly more expensive and costly to replace than the filter itself. Most UV filters have special optical coatings, but there is the potential for some cheaper UV filters to increase the likelihood of lens flare. They can also cause vignetting when further filters and filter holders are applied (especially with wide-angle lenses]. In some cases they can even reduce image quality. For these reasons, some photographers decide not to use a protective UV filter and prefer to simply take care to avoid damage to the lens. To deal with some of these considerations, manufacturers also now produce totally neutral and optically tested filters specifically designed to be used purely as lens protectors.

Another well-established and popular filter is the circular polariser. This can be used to enrich the colour of a blue sky, reduce reflections in water and boost saturation and apparent contrast.

The filter is rotated until the desired effect is visible, with the strength of the filter depending on the precise angle of the light. Circular polarisers are available either as screw-on filters that attach directly onto the lens itself or as part of a wider filter system, in which case they can be slotted into either the very back or front of the manufacturerdedicated filter holder.

The only thing you have to be aware of when using a polariser is that you do lose about two stops of light, meaning that a 1/125sec exposure at f8 becomes a l/30sec exposure at f8 or a 1/125sec exposure at f4, so either shutter speed or depth of field will be affected. This can, however, be an advantage when photographing a waterfall or stream in a forest as not only can the filter be used to reduce or remove reflections, it can also be used as a makeshift ND filter, helping to achieve a longer exposure time to capture the movement of the water.

Despite any slight challenges it might present in usage, the way in which a polariser impacts on colour, saturation and contrast is hard to reproduce precisely in Photoshop while the removal of reflections is all but impossible. As a result, most landscape photographers (and travel photographers) carry a circular polariser with them at all times.

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Neutral-density graduated filters-generally referred to as ND grads-have always been popular with photographers. Even since the digital revolution, they have remained popular photo accessories. These filters are incredibly useful when you want to balance the exposure for a scene with a large contrast range.

Once again itthe world of landscape photography where these types of filters are most useful. The most obvious real-world example is when the foreground is fairly dark (requiring a longer exposure) but the sky is relatively bright (requiring a shorter exposure). Using a two-stop or three-stop ND grad allows you to shoot using the appropriate exposure for the foreground without causing the sky to overexpose and lose detail. While it is possible to shoot two separate exposures and then merge them into one during the editing process in post-production, this obviously takes more time and can also be fiddly with some scenes, so using an ND grad during capture has a big time-saving advantage here.

Graduated filters such as these are available with either a hard or soft ’to the transition, allowing you to choose which is most suitable for the scene you are capturing. To use a graduated filter, you simply slide the filter into the appropriate filter j holder and position the filter as required. This is generally easier when using Live View, or with the depth-of-field preview button depressed.

A close relative of ND grads, ND filters do a very similar thing but are ’, rather than graduated. These filters have not only remained popular but have actually increased in popularity in recent years, partly because their effect can be seen and evaluated incamera, making their use more reliable and predictable. These filters affect the entire area of the image and can be purchased either as screw-on or slot-in filters. A wide range of strengths are available, all the way from one-stop ND filters (with an optical density of 0.3) to ten-stop ND filters, which have an optical density of 3.0 and can be used for incredibly striking, creative effects. These filters have become particularly popular with coastal photographers as they allow you to capture images with smooth clouds and velvety seas. However, they can also be significantly useful for architectural and urban photography, as itpossible to significantly reduce the appearance of people and traffic in the image by using a very long exposure time of twenty seconds or more, as each person isnstanding anywhere long enough for the sensor to record them.

Extreme ND filters, like LeeBig Stopper ten-stop ND, can produce a colour cast that can confuse your cameraauto white balance, so youneed to experiment with how your DSLRsensor responds to this and be prepared to set your white balance accordingly. Obviously, if you shoot RAW, this isnan issue as you can tweak the white balance using your RAW conversion software. The Lee Big Stopper (or any ten-stop ND filter) needs to be used with a scene with lots of movement in it (such as a beach with crashing waves or a moody sky with dramatic, fast-moving clouds) or yousimply extend your exposure time for no good reason.

Using filters is a great way of reducing the amount of time you have to spend editing and processing your images in front of the computer. Therealso something of a thrill to be had in the way filters I force you to be even more methodical in-camera.

5 expert tips for using filters

1 Keep your filters as clean as possible for the best image quality

2 Store your filters carefully in transit as they can easily get damaged

3 Buy the best-quality filters that you can afford to avoid replacing later

4 A ten-stop ND filter can be very expensive and wonbe ideal for everyone-try before you buy!

5 Practise with your filters before using them in the field for the best results

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Filter power

1 Control dynamic range for well-exposed, evenly lit images

2 Create dramatic, silky skies with the capture of fast-moving clouds

3 Easily remove people, birds and traffic from your photographs

4 Make waterfalls, oceans and rivers record as perfectly smooth surfaces

5 Shots need minimal editing, which means less time on the computer!

Essential filters for landscape captures

1.2 ND filter

ND filters simply reduce the amount of light that reaches the sensor through the lens. They can be purchased in various strengths, with two, three and four stops (with an optical density of 0.6, 0.9 and 1.2 respectively) being the most common and useful types.

ND grad

These rectangular filters are very similar to NDfilters, except they have a gradient, so approximately half the filter is totally clear. This allows you to position the neutral density half of the filter over half of the frame, typically a bright sky, to balance the exposure.

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Polariser

A polariser filter has a similar effect to putting on a pair of sunglasses. Colours are enriched and the contrast between skies and clouds is increased. It can also be used to reduce or even eliminate reflections. They tend to only work well at specific angles and certain times of day.

The Big Stopper

Lee s Big Stopper, popular with landscape photographers, extends exposure time by ten stops. This extreme effect means you can achieve very long exposures in all but the brightest light. Youneed a solid tripod and the right scenery to make the best use of it, though.

All about Leefamous Big Stopper filter

1 The right scene To make good use of the Big Stopper, you need a scene with movement. If every element of your scene is static, all this filter will do is extend your exposure time for no real advantage.

2 Bulb mode Use your camera s Bulb setting, with a narrow aperture of f11 or smaller. Ituseful to have a remote shutter release with this, to avoid pressing the shutter button at the end of the exposure.

3 Tripod support Make sure your tripod is as stable as possible. If you have a spirit level to hand, place it in the camera s hotshoe and keep an eye on it for any movement or vibration during the exposure.

4 Check and review Digital comes into its own here, as you can check the success of the exposure. Don t be surprised if your first attempt is too dark and you need to do a second, longer exposure.

ND filters effects Removing people from the frame

1 Pick your spot Find a spot where you wonbe directly in anyoneway. You don t want people walking right in front of the camera during the exposure, and you certainly donwant your tripod to be knocked or disturbed.

2 Compose and focus Remember that you will need to compose and focus your shot before attaching the Big Stopper as you wonbe able to see anything through either the LCD or the viewfinder once the filter is in place.

3 Remote release Use a narrow aperture (smaller than fll) and set your camera to its Bulb setting. Again, a remote shutter release cable or wireless trigger is beneficial to avoid pressing the shutter button to end the exposure.

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