HOW TO USE ND FILTERS?

They look like a simple piece of grey plastic or glass and they simply reduce the amount of light reaching the sensor or film. But ND filters are invaluable for creative shutter speeds and apertures.

YOU CAN GET A PRETTY good idea of the effect of the other filters we've covered like grads and polarisers by simply looking through the filter, or better still, the viewfinder of the camera. Look through and ND filter though, and all you'll see is a darker image, so the effect isn't immediately obvious. It's easy to confuse these filters with ND grads too, especially in conversation, but you can't mistake the two filters in the flesh. The overall ND filter is simply a grey filter that cuts down the amount of light reaching the sensor or film, but start using them and you'll soon find they're an invaluable aid to expanding the shutter speeds and apertures available when working outdoors. ND filters commonly come in different strengths, reducing the light by 1, 2 or 3 stops. To confuse matters, the manufacturers give the various strength filters different number. Cokin and Hoya call the 1-stop reduction ND2, 2 stops ND4 and 3 stops ND8. Which filter to use is simply down to the amount you need to alter the exposure by. A 2 or 3-stop ND will be the most useful choice, giving you the opportunity to use a wide range of shutter speeds or apertures to get the desired result.

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Reducing the amount of light by using and ND filter can also be useful for achieving shallow depth-of-field effects in bright conditions. This is especially true if you have a digital SLR that has a minimum ISO of 200, such as the Nikon D40 or Pentax K100D. You'll find that shooting in the middle of the day or into the light, even with the fastest shutter speed you can get, you'll only be able to use an aperture of f/5.6 or smaller. Fitting a 2-stop ND filter over the lens will allow you to use an aperture of f/2.8 at the same shutter speed, giving you a much shallower depth-of-field.

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In many situations you can, but there are times when you'll find that even using the smallest aperture available on your lens won't give you a slow enough shutter speed to blur movement in the scene, such as water or clouds, and this is where the ND filter comes in. By reducing the amount of light passing through the lens and into the camera you can use a slower shutter speed at the lowest ISO setting available on your camera.

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Filter Tip:
Using flash in bright conditions is great for lightening shadows on your subject, but many cameras have a limited maximum shutter speed that will work with the flash. If you want to use a wide aperture such as f/4 or f/5.6 in bright conditions, to get the right exposure you need a shutter speed that's faster than will work with the flash. An ND filter will let you use both these apertures and the flash.

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• B+W Neutral Density Filters
• HOYA Neutral Density Filters

Relative Reading:

• Which filters do I really need?
• How to use a POLARISER?
• How to use ND GRADS? 　

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