How To Use Graduated Filters

Graduated filters (grads) come to the rescue of landscape images spoiled by bland, washed out skies. If you live in a climate where these skies are the norm, then these are the landscape photographer's best friend.

What's A Graduated Filter?

It's all in the name. Quite simply one half of such a filter (grad) is darker than the other, while the other half - in most cases - is completely clear. These filters also fall broadly into two camps - those that are colored and the grey or neutral density grad. I'll ignore the colored versions for the moment and concentrate on the more useful, and subtle, grey and neutral density filters.

Both of these do the same job, reducing the brightness difference between the sky and the ground, thereby allowing your film or digital sensor to record detail in both these areas. The difference between the two types is in the consistency of the color - a neutral density grad shouldn't cause any color casts on the sky, whereas the cheaper grey grads can often produce unwanted colors. For the most consistent results Lee Filters is among the best and most of the landscape professionals use its products.

Neutral density grads are also given numbers which tell you exactly how many stops of light they're going to reduce the brightness by, while with grey grads it's much more hit or miss. So if you can afford it, neutral density grads are the ones to go for, although a grey grad makes a good alternative. The filters come in three strengths, although there are two ways used by different manufacturers of indicating those strengths:

What The Numbers Mean
ND Type	B+W, Cokin, Hoya	Lee, Tiffen
1-stop	ND2, ND2X	0.3 ND
2-stop	ND4, ND4X	0.6 ND
3-stop	ND8, ND8X	0.9 ND

If you're on a budget and can only afford one neutral density grad, the most useful will be a 0.6 hard grad.

Metering Your Shot

The whole reason for using a neutral density graduated filter is to control the exposure difference between the sky and the ground, so you'll need to take control of the light metering to make full use of the effect. Ideally you'll set your camera to manual so that the settings don't change when you start using the filter.

Your first step is to determine the strength of filter you'll need. The simplest method is to take a meter reading with the ground filling the whole of the frame without the filter in place. Now repeat this step but this time with the sky filling the frame. The difference between these two readings will indicate the strength of graduated filter that you need. A 1-stop difference in the readings will need a 0.3 ND graduated filter, a 2-stop difference a 0.6 ND grad, while a 3-stop difference will require a 0.9 ND grad. My most often used filter is the 2-stop (0.6 ND one), with the 3-stop (0.9 ND) being used only occasionally. So, if you're only going to buy one graduated neutral density filter, the 0.6 ND is the one to buy. For some reason, 0.6ND Cokin filters are hard to come by. Cokin, however, provide the grey versions of graduated neutral density filters rather than pure neutral density filters which is reflected in their cheaper price. If you're serious about color reproduction (i.e. avoiding color casts) then the Lee filters are the better ones to go for.

Once you've decided on the filter you need, use the meter reading you took from the foreground to take your shot.

You should now find your filtered image is perfectly exposed throughout.

The sun just breaking through the clouds gives lots of contrast between the sky and the foreground. Exposing for the foreground grass gave an exposure of 1 second at f/22, while the sky gave 1/6 sec at the same aperture, producing an almost white sky.	By exposing for the foreground and using a 0.6 Neutral Density graduated filter, to compensate for the 2-stop difference between the sky and foreground, there's much more cloud detail. With the grad positioned just below the horizon, there's also more detail in the hills in the far distance.

Positioning A Graduated Filter

All graduated filters need careful positioning to get the best effect. To make the most of this your camera should be fixed securely to a tripod - which is always a good idea for landscape shots anyway. This allows you to slide the filter accurately into position, so the transition from clear to dark falls on the horizon. If your camera has a depth-of-field preview facility that stops the lens down while you're looking through the viewfinder then use it. The darker viewfinder image will make it easier to see the position of the filter.

With the camera on a tripod, carefully position the graduated filter so the transition falls exactly horizontally on the horizon.	A badly positioned graduated filter will give uneven lighting. It's easy to miss this if your front element - and therefore filter - rotates when you focus.

Graduated Filters To Avoid

Colored graduated filters may look eye-catching but they're best avoided. Here are three filters that are best avoided:

Blue Graduated Filter This filter can help when you've got a clear blue sky, but if you use a blue grad when ther are clouds around and they'll be turnen an (unfetching) unnatural shade of blue as well. For natural looking skies, stick to grey or neutral density graduated filters.

Fluorescent Colored Graduated Filter It's striking, but in all the wrong ways. The 'nuclear winter' effect produced by brightly colored graduated filters only looks good (actually, they still look pretty bad) in low-budget sci-fi movies.

Tobacco Graduated Filter Sickly brown skies don't do your landscape photos any favors. So leave this type of filter to the car advertisers and holiday companies. It's got no place in your photographs.

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Lee supply filter sets which let you save on the cost of buying the filters separately. They provide two filter sets, one tailored for wide-angle lenses, which have a soft transition area between the neutral density and clear areas of the filter; the other set gives a hard transition area and is better suited to standard and telephoto lenses. If you decide to use the Lee filters, they have a Filter Holder Kit which will let you use up to four filters at any one time. Adaptor rings to use the filter holder with your lenses are available from Adorama.

Cokin" filters are 3-4 times cheaper than Lee filters but thir quality isn't as optically good. But, if you're new to using graduated filters, this is a good system to start with and you can always upgrade to Lee at a later stage if needs be. Cokin also supply a filter holder for their filters that allows up to four filters to be used at once.

One thing to note is that Lee filters, at 6x4", are physically larger than Cokin fillters (2.5x2.5") so if you own lenses that have large front diameters, you may get vignetting (darkening of the corners in a photo) when using the Cokin system.

I used the Cokin system very happily for many years but I'm now making the transition to the Lee filters because of their higher quality and the sets they offer that suit landscape photography. In addition to the neutral density sets I mentioned above, they also have these sets (all contain three filters):

Landscape Resin Filter Set - a Real Blue 2 Grad which gives a deeper hue to blue or grey skies, a Straw 3 Grad, which when inverted adds warmth to the foreground, and a sepia 2 Grad, a deep chocolate colour which enhances rocks, foliage and fallen leaves.
Autumn Tint Resin Filter Set - Tobacco 2, Coral 6 and Chocolate 2 filters, can be used to create atmospheric autumnal effects.
Sunrise Resin Filter Set - A set of three bright, warm colours for dawn or sunrise photography. The Straw 2 Grad filter is a fairly strong yellow and is a good warm-up filter. Mahogany 1 Grad helps achieve a paler sunrise effect, while placing the Straw Stripe across the horizon adds warmth.
Sunset Resin Filter Set - Sunset red Grad, Sunset Orange Grad and Sunset Yellow Grad. This offers the photographer the flexibility and control they need to achieve the result they want, adding warmth and definition to both sky and landscape.
Mist Resin Filter Set - a Graduated Mist, a Mist Stripe and a Mist Clear Centre Spot. These filters can be used individually or in combinations to create varying densities of mist and fog.

And those are just a few of the filter sets available.