Filters for Digital SLR & Mirrorless Cameras
Filters were a valuable part of most photographer's kits in the days when 35mm film dominated the market. Filters were used to protect the lens, to warm the image, to polarize the light, to correct artificial light, to soften the image and much more. Colored filters were essential for black and white photography to emphasize light and tone.
With modern digital slr cameras and imaging software such as Adobe Photoshop, most filters no longer play a major role in digital
photography as many of the filter effects can be carried out by white balance, within the digital SLR or through digital imaging on a computer.
Filters which may be of use in digital slr photography include polarizers, infrared and neutral density filters.
A polarizing filter can be useful in reducing reflections or glare in glass or water. Colors can also appear deeper with a greater contrast between the sky and land. To avoid exposure problems on a digital slr camera, only buy a circular polarizer as opposed to a linear polarizer.
Neutral Density Filters
A neutral density filter will reduce the amount of light entering the lens without affecting the color of the image and can be useful in bright conditions when fast shutter speeds are required. The filters come in various densities and are labelled with filter factors. For instance a neutral density filter with a ND2 filter factor will reduce light by one f-stop while ND4 will reduce light by 2 f-stops and ND8 by 3 f-stops. Split neutral density filters can be used to balance light or detail as half the filter is clear while the other half reduces light.
Infrared filters filter out visible daylight and produce images with a ghostly effect. Since an infrared filter eliminates visible light, focusing and exposure will have to be done manually as there will be nothing visible in the viewfinder. To take an infrared image, place your digital slr on a tripod and remove the infrared filter. Focus the lens manually and then place the filter on the lens. Set exposure to manual and experiment with slow shutter speeds such as 3 or 4 seconds as there is very little light available for the exposure.