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21.02.09
Why you need filters
Words by Will Cheung
Say the word ‘filters’ to one photographer and they’ll think you’re talking about those dodgy effects you get in Photoshop. Use the same word to another snapper and they’ll automatically think of the high-quality plastic and glass you put in front of the camera lens. Well, to avoid any confusion right here and now, let’s make it clear we’re talking about filters you use on your camera’s lens.
With the boom in digital imaging you could be forgiven for thinking that such filters are redundant, because almost any effect can simply be replicated on the computer afterwards. In principle, shooting without any filter on the lens and reproducing the effect afterwards on the computer sounds sensible; it means you always have an unfiltered original to play with. Indeed, many photographers work this way, including pro Mark Sunderland.
However, I think there’s something quite special about adding effects at the time of taking. You could say that using filters is part of the craft and skill of pre-visualising an image and getting it right in-camera. Then on the computer, you can do any little tweaks that you usually do before printing the image out and sticking it on the wall.
To be fair, there’s no right or wrong in either approach. It’s up to you to decide which method works best for your photography. There are hundreds of different filter types, although many are a variation on a theme. The graduate filter is a good example here. You can buy graduates in a multitude of colours, in varying densities and gradation styles to suit different needs, tastes and situations.
In my opinion, and this is a contentious point, for the keen landscaper, there are three types of filter to consider keeping in your kit bag. These are the graduate filter, the single colour and the polarizer. Leaving aside the latter, which we’ll come back to very soon, that means you could still be lugging 100 filters up hill and down dale. Of course, that would be plain daft so our guide here concentrates on the graduates and plain coloured filters you really, truly, truly need. But first turn over to find out all you need to know about polarizers.
POLARIZERS
The polarizer is the single most useful camera filter money can buy. It’s versatile, easy to use and will undoubtedly improve your photographs. The other thing with the polarizer is its effect can’t be realistically emulated digitally, so using one on camera is the only option.
The polarizer has five fundamental uses. It:
- Intensifies blue skies.
- Eliminates glare thus enhancing colour saturation.
- Cuts down reflections off water and glass.
- Helps cut through haze.
- Absorbs between one and two f/stops of light so can be used as a neutral density filter.
If we’ve convinced you to buy one, you’ll come across the terms ‘linear’ and ‘circular’. This has nothing to do with the filter’s actual shape. A circular polarizer is a linear polarizer with the addition of something called a quarter-wave plate. As most photographers use an autofocus SLR (or one with selective or spot metering) you’ll need a circular polarizer to ensure correct exposure and focusing.
If you’re using a manual focus, non-spot/selective metering camera, you’ll need a linear polarizer. In fact, you can use either polarizer type on any camera. No one’s going to serve an ASBO on you for doing so, but use a linear polarizer on an AF SLR and focusing and exposure may go awry so you’ll have to take control.
Once you’ve bought it, using a polarizer isn’t difficult. Slip it on the lens and rotate the filter holder or the polarizer in its mount and check out the effect in the viewfinder. If there’s a blue sky and the sun’s shining or the camera lens is at the right angle to the subject, the filter’s benefit is immediately apparent. On a dull day or if you’re shooting at an unsuitable angle to the subject the polarizer’s effect is negligible or even non-existent.
A little knowledge and experience will help you understand when the polarizer will be most effective. For example, I said earlier that it cuts down reflections off glass and water, but this only applies if the lens is around 45° to the reflective surface and shooting from straight on has no effect.
The polarizer’s ability to enhance colour saturation across a range of subjects is one of its greatest benefits. For more about blue skies. It makes a massive difference with subjects like painted areas, foliage and rocks, brickwork and so on, again when used at around 45° to the subject and with the sun out. It removes all the polarized light, ie. glare, reflected from the subject’s surface and produces areas of rich solid colour. The effect can be mightily impressive.
Landscapers will also enjoy the fact that a polarizer can absorb up to two stops of light. If you want to use a slow shutter speed on a bright day, this light loss comes in really handy. It means, for example, that you can shoot at 1/15sec instead of 1/60sec – of course, with the camera on a tripod – so you can blur that waterfall.
Despite all the polarizer’s benefits there are times when it’s not worth using – or at least using with care.
On cloudy days the polarizer’s benefit is minimal. Furthermore, with lower light levels, the light loss can mean slower shutter speeds, and with it, the risk of camera shake.
You need to be more wary with wide-angle lenses too, which can give a patchy effect across a blue sky. Many a great landscape has been spoilt by this effect, but it can be used effectively with the right composition.
Finally, go somewhere with vivid blue skies (Greece, Spain etc) and the polarizer can have such a dramatic effect that a sky can appear black, which looks horrible. Watch the subject as you rotate the polarizer to avoid such problems.
To be honest, though, the downsides of a polarizer are so few and the benefits so significant that if you only buy one camera filter make it the polarizer. And buy the best you can afford. Cheaper models might save you a few quid, but if it affects image sharpness or adds a colour cast (this used to be a big problem with film) to your pictures, that saving is pointless and you’ll end up buying a decent model eventually anyway.
You do need to consider which lenses you intend using with it. Polarizers come in mounts of different thicknesses and with extreme wide-angle lenses, this can cause cut-off or vignetting in the corners of the frame. Hoya, for example, has a range of slim profile Super HMC Pro-1 filters to avoid such problems.
There’s also the question of buying into a filter system or a screw-in:
WHICH FILTER SYSTEM
Start investing in filters and there are many decisions to be made. The first is which filter type should you go for. Round filters, such as those from B+W and Hoya, screw onto the front of the lens, but this means if you have one lens with a filter thread of 58mm and another of 77mm, you’ll need two filters.
Square or creative system filters, such as those from Cokin and Lee Filters, fit into a holder. In turn, this slips onto an adaptor ring that fits on the lens. This means you can have one filter, one holder and two adaptor rings, one for each lens. There’s no right or wrong way and most photographers end up with some of each.
RULE OF THUMB
The amount of polarized light in the sky varies with more of it at right angles to the sun, which is why a blue sky deepens most in these areas when a polarizer is used. As a good guide, point at the sun with your forefinger and stick your thumb straight up.
Now rotate your wrist and where the thumb points is where the polarizer has the greatest effect. Because of this, use a lens wider than 24mm in the 35mm format (16mm in APS-C format) and you will notice that a polarized blue sky will appear uneven. This can be annoying so it’s something to be aware of. If you don’t like the look of it, the only solution is to shoot without a polarizer or just be much more considerate with the composition.
For information about camera filters, please contact the following manufacturers and mention PM if you are asked.
B+W 0870 444 6561
bpluswfilters.co.uk
Cokin 01628 674411
cokin.co.uk
Jessops 0800 083 3113
jessops.com
Kood 01727 823336
kood-international.com
Lee Filters 01264 366245
leefilters.com
Marumi 01793 615836
kenro.co.uk
Sigma 01707 329999
sigma-imaging-uk.com
SRB-Griturn 01582 661878
srbfilm.co.uk
Tiffen 020 8236 1212
tiffenfilters.co.uk
Heliopan 020 7323 6455
teamworkphoto.com
Hoya 01628 674411
intro2020.co.uk/pages/hoya.htm
GRADUATION DAY
While the polarizer is ‘the’ must-have filter, the graduate filter runs it a very close second. The toned area of the graduate filter reduces the amount of light reaching the film or sensor. Thus, for landscape work it helps control contrast between the dark foreground and the brighter sky, adds colour where there isn’t any and can inject a dose of mood into a flat scene.
Where the graduate filter differs from the polarizer is that there’s no one filter capable of fulfilling a photographer’s many needs, which explains why there are so many options. A look at Cokin’s P-range revealed no fewer than 38 colour variations on the theme and even more in the Lee Filters range.
There’s a broad choice of colours, density and graduation style. What style of graduate you need depends on your tastes, but ask an experienced landscaper what to use and you’d probably get a list of grey, warm-up and blue, in that order of priority. There are plenty more vibrant outlandish colours available which are less useful.
Personally, I’d suggest starting with these three: two grey neutral density graduates, a two-stop (ND4) and a three-stop (ND8), and a warm-up such as Coral, pink, tobacco or orange to intensify an orange sky.
And while there are round graduate filters available, this is one filter type where it’s best to invest in a creative system, such as that from Cokin or Lee Filters. With this filter type moving the filter up or down in the holder to suit the scene is easy.
Filter positioning and aperture choice are two aspects to consider. Position the filter incorrectly and you can darken the wrong area while choosing an unsuitable aperture might make the colour change too obvious or too subtle. Most SLRs have a depth-of-field preview so you can check the effect in the viewfinder before taking the picture.
Metering is something to take a little care with. In an autoexposure mode, slipping a graduate filter into position can fool the meter into thinking that the light has gotten worse and the meter will compensate and thus overexpose the foreground, which is not a good thing.
On a DSLR this is easy to check on the monitor. And if you do experience the problem the easiest way round it is to meter without the filter in position, use the camera’s autoexposure lock (AE-L) to memorize the reading and then position the filter and take the shot. Or meter manually.
Once you start using graduate filters, you’ll be wondering how you coped without them. While you can add the effect on the computer, there’s much satisfaction to be had from getting it right in-camera so give them a go.
TECHNIQUE
Using a filter increases the risk of flare or ghosting when shooting towards the light. Most filter systems offer a lens hood to help and this bellows model shown here is from Lee Filters. However, using a sheet of card or your hand can be more effective.
If you see flare in the viewfinder, stretch out your left-hand and shield the front of the filter surface from the light. It’s easier with the camera on a tripod, but it can be done handheld – providing you’re not using a long lens, of course. By adjusting hand position you should be able to stop flare and not include your hand.
USING CONTRAST FILTERS
Single-coloured contrast filters can be used on your DSLR to give better monochrome shots, but you may have to set the camera to black & white. You may also have to shoot JPEGs depending on your camera. These three shots were taken early evening on a Canon EOS 5D DSLR in Raw format, but with the colour settings set to Monochrome so the images were shown on the monitor in black & white.
Interestingly, in Photoshop, the two filtered images appear orange and red, as you’d expect, but through Canon’s DPP software they are black & white.
SINGLE COLOUR FILTERS
There are two types of single-colour filters. There are colour correction filters such as the blue 80 and 82 series and the brown 81 and orange 85 series. These are used to add an overall colour tinge, say to cool down (80, 82) or to warm up (81, 85) a landscape scene.
While these filter types are subtle, contrast filters are much more vivid and are primarily used for black & white photography, particularly with film. Yellow, orange and red are the most popular and will all make more of a blue sky, with red being the most powerful.
Use these contrast filters with colour film or a digital camera in its normal mode and, obviously, the image comes out with a vivid yellow, orange or red colour cast. However, change your digital camera to its monochrome mode and you can enjoy the contrast-enhancing potential of these filters. It’s worth noting that their effect isn’t as apparent as with black & white film, because camera sensors have a more balanced sensitivity to the different wavelengths of light.
The colour correction filter type is still widely used by scenic photographers to enhance the mood of an image. For instance, an 80A or 80B would really enhance the blueness of a twilight. An 85B or 81D warm-up could be used to make a glowing sunset even more impressive.
Many photographers will also use such filters in combination with a graduate or polarizer. In use on the camera, using such filters is pretty straightforward. Screw the filter onto the lens or slip it into the holder and shoot away. The filter factor is automatically accounted for by the camera’s meter so no exposure adjustments are necessary.
Because single-colour filters are so simple, these are also the simplest filters to replicate digitally. Many imaging software packages do a convincing job and the effect is very controllable.
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