Tip 4: Neutral Density Filters

In one of my earlier tips, I mentioned the use of neutral density filters to extend shutter speeds and allow for capturing movement.

Quite simply, a neutral density filter is.... "Neutral" in it's effect on colour (at least the good ones are) and effects the "density" or amount of light entering your camera.

Neutral density filters are available in a range of "stops" (eg how much their density effects the light... each "stop" halves the amount of light entering) and are uniform in their effect across an image. Naturally, these are particularly useful when the lighting is too bright for your desired shutter speed and aperture combination, but control the light and you can control other elements of your images also....

An example of where this would be useful is a flower with a relatively close background. You may wish to isolate the flower from the background using a shallow "Depth Of Field" technique (...or "DOF" - the area of the image that is in focus)... this would require a wide open aperture (small f-number on lens) to minimise the DOF, but this may also let in too much light. You can compensate for this by using a faster shutter speed, but should this still not be enough, a neutral density filter (or filters) can be used to decrease the light, so that a correct exposure can be achieved at the wider open aperture.

These examples display the shallow DOF technique. You will notice that the first image has greater DOF and the background is a bit distracting because of it's sharper focus. To make the DOF shallower and isolated the flower more, a wider aperture has been used in the second image.



Now the experienced reading this will look at the image and say "the light shown here could easily be controlled with a faster shutter speed" and they would be absolutely correct, but the results in the above "examples" are exactly what would be achieved with the use of neutral density filters in excess light situations.

The last example is probably the most common use of the neutral density filter. It displays how a longer shutter speed has been used to highlight water movement. In this case a lot of DOF was achieved by using a small aperture (larger f-number on lens) and this smaller aperture also reduced the amount of light entering the camera and thus extended the shutter time, allowing the water to blur.

To further enhance this movement and produce a smooth flow, the use of a neutral density filter has lessened the light and extended the shutter speed required for correct exposure.

Shot's like this are easy in the low light conditions of early morning or late afternoon, but try this in bright midday sun and it becomes almost impossible, as the shutter speeds required for correct exposure (even at the smaller apertures) are too fast to allow water "flow" like this to be captured.... this is where the neutral density filter becomes an invaluable tool for the photographer.

Naturally where long shutter speeds are utilised (longer than 1/60 sec) the use of a tripod is recommended.

Cheers

Rusty
Australian Digital Photo Of The Day:
http://www.potd.com.au

Although I now use the Lee Filter System, I had great success with the Hoya HMC ND400...


Tags: neutral density filter long exposure nd nd400 nd-400 lee filters photographic photography big stopper