Filter tips - Architecture


	Because a polariser absorbs about 1.5 to 2 stops of light, they can be useful for producing lengthy exposures to remove people walking in your shot, as this view of York station reveals.

It's so easy to over equip yourself with photographic paraphernalia you think might be useful, one day. Remember all those accessories and odd items that you were convinced you couldn't do without on a shoot, only to realise they have lain dormant in the darkest recesses of your holdall since the year dot. There are, however, one or two items you simply cannot afford to be without as an architectural photographer - namely a carefully selected set of filters.

The role of any filter is simply to improve or enhance the final image. It is not to add unwanted visual gimmicks, or to try forlornly to make a good shot out of a bad subject. Filter effects should, in fact, be so subtle that the use of any aid on the front of the lens is not apparent. So if you can immediately tell a filter has been used, the photographer has arguably failed in that instance.

If you were restricted to just one filter, make it a polariser. This type has so many uses it really can be described as an essential. Pick one up and the first noticeable aspect is the darkness or density of the glass - they often absorb up to 2 stops worth of light. Yet even this facet can be put to good use, if you need a very long exposure of several seconds to allow people to move and therefore 'disappear'.

The main functions of the polariser are to control reflections from shiny surfaces such as glass, plastic or water, remove glare and to saturate colours. How does a polariser work? Here's the theory, in a nutshell - light waves normally vibrate in many planes, but when reflected from a smooth non-metallic surface, only one plane remains. When a polariser is fitted in front of the lens, it too allows light of only one plane to pass through. Rotate the filter while observing the image until the reflection disappears or is minimised.


A polariser can be used to remove reflections in a buildings' shiny panels, or accentuate them when rotated to a different position as here.

Lots of modern buildings feature totally glazed walls, often in a dark tint to protect the workers inside from the full strength of the sun. It is fascinating to use a polariser in this situation, find yourself a good viewpoint where the reflections are significant, then watch how they change as the polariser is rotated. Even slight differences in angle can make big alterations to how the image appears.

In brighter lighting conditions glare is often a problem from paintwork or panels on a building, or foliage positioned alongside. Adding a polariser can cut these highlights down and help keep colours looking as they should. Unfortunately polarisers don't work well with reflections off metal surfaces such as chrome or polished silver.

The final benefit of the polariser is the extra saturation it gives to colours, which really leap out of the transparency on a lightbox. Never is this more true than when a blue sky is behind the subject, and the camera is approximately at right angles to the sun position. This allows a strong deepening of the blue to occur, without affecting other colours. Compared to a shot taken without a polariser, the results are amazing.


	Another function of the polariser is to saturate colour, as this striking South African shot demonstrates. Just look at the depth of that blue sky!

Graduated filters are another type that merit inclusion in an outfit bag. Clear at the base of the filter, then graduated over several millimetres at the top, these filters serve two main functions. The first is to control contrast by reducing light transmission in bright skies, while the second is to add subtle colour where it is lacking in the available conditions. I have several, including two grey grads of different densities, plus several warm and coloured versions.

Usually an architectural shot needs to shows as much contrast as possible, but just occasionally you might want to go the other way and suppress details. This is usually when a nostalgic mood is being evoked, often with an older building rather than a stark modern edifice. At these times a diffuser or soft-focus filter is a boon, as it blends highlights into the shadows and thus reduces contrast.


A more realistic interpretation of a polarised blue sky from England, aided by the contrast with the fluffy white clouds.


In backlit situations, a carefully positioned grey grad can help control the contrast between bright sky and foreground. Without the filter on the building and sky, it would have been too pale and the sky would have lacked any tone.

There are three main types of soft-focus filters to consider - mist, fog and diffuser. Mist filters are etched with fine lines to spread the image into the shadows, fog filters do the same thing only to a more pronounced level, and diffusion filters which are the mildest of the three. Bear in mind you won't achieve a solid black anywhere in your image if any of these is fitted to the lens. Each type is available as a plain design where the effect is even across the whole filter, or with clear centres so that only the periphery is affected.

Some of the most effective architectural images can be taken in good old monochrome, where the absence of colour enables the form and texture of a structure to be more clearly viewed. Black & white can add drama to a building and its surroundings, as the mood can be manipulated during the printing process. Whereas a blue sky with fluffy white clouds looks more like a picture postcard when colour is present, the same sky rendered in monochrome can take on a really brooding presence as the blue sky can be turned dark or even black! White clouds now stand out in supreme contrast and the whole effect can be quite surreal.

The golden rule to remember when a black & white film is loaded in your camera is that a filter of any particular colour lightens the same tone on the final print and darkens its opposite. That's why a green filter is a favourite among monochrome enthusiasts, as foliage is rendered lighter, while a yellow or orange filter can produce progressively darker sky tones. A deep red filter renders blue sky as jet black, and turns any red colours in the scene pale in tone. The aim is to enhance tonal separation when colours are reduced to shades of grey in the finished picture.

With this interior scene a grey grad was used to tone down the top half of the image, so that the light flooding through the roof could register along with the darker elements by the floor.

For this view of Bath's lovely architecture, a warm grad was employed to enhance the sky, adding tone, detail and warmth to the otherwise coolly lit scene.

A plain diffusion filter was employed here to soften this quaint harbour scene. Though very much shot in the present, it paints a picture of times past.