Photo Filters

Photo filters are transparent or translucent glass or gelatin elements that fit onto the front of a lens. They alter the characteristics of light passing through the lens or add special effects and colors to a photo.

Filters come in two different types, screw-in filters and slot-in filters. Screw-in filters screw into the lens barrel threads called the adaptor ring. Each filter is designed for a specific focal length. They're fixed to the lens until you manually unscrew them. For slot-in filters, a filter holder is placed on the lens adapter ring and the filters are dropped into the holder. The holder usually has interchangeable adaptor rings, so it can fit on several different size lenses. The holder has three or four slots in it, so you can put more than one filter in the holder. The big advantage with the slot-in filter system is being able to add or subtract filters relatively quickly and larger filters can be used with shorter, smaller lenses.

There is a wide array of filters that you can use, but the most commonly used ones are the Ultraviolet (UV) filter, the polarizer, color balancing filters, Neutral Density (ND) and the soft focus filter. In addition, B&W photography has specific filters that affect specific wavelengths of light.

The first thing you have to recognize when using filters is that they change the dynamics of light and they affect the intensity of light hitting the sensor, so you'll have to adjust your exposure. This is called The Filter Factor. With digital cameras, you can immediately see the effects on the light quality and intensity and adjust your setting accordingly.

UV and Polarizing filters reduce the haze created by ultraviolet sunlight and reflected light. Polarizer filters remove reflections in water and glass, so that when angled properly you can shoot directly into those substances and see right through them. UV filters reduce haze caused by sunlight.

Color balancing filters aren't totally necessary with digital cameras because you can change the white balance at will. Color balancing is necessary when your light source doesn't match the White Balance that the camera is set to recognize. Daylight records as "blue" when the camera is set to tungsten or incandescent light, and tungsten light records as "orange" when the camera is set to daylight. In addition, fluorescent light sometimes photographs "green." You may be familiar with these color casts.

A color balancing filter either completely corrects the light source differential, or provides partial correction. Partial correction is where and how you can be creative, as these filters can either just slightly or dramatically cool down or warm up a photograph. Many higher end dSLRs allow you to be extremely precise with setting the color balance, so you can set your "white point" to perfectly match the specific lighting conditions you are facing. With a dSLR you would use color balance filters to enhance an effect, not actually correct the color balance.

Neutral Density (ND) filters don't affect the dynamics so much as they affect the light's intensity uniformly across all spectrums. NDs allow for longer shutter speeds or larger apertures where the setting would normally overexpose the image sensor. For example, if you want to shoot outside on a bright day, your meter will tell you to set the aperture to f/11, which will give you a deep depth of field. However, you may want a shallow depth of field, and to do that you need to have a wider aperture. By putting on an ND 9 filter, which deducts 3-stops of light, you can shoot at f/4 and achieve the shallower DOF. Or if you're shooting inside, and the light coming in from the window overpowers the inside lights, using the ND filter would allow for a more uniform exposure.

With a digital camera, you might not want to use specific B&W filters because you can achieve similar effects during post processing in Photoshop. However, if you're not terribly Photoshop savvy and want to use the B&W setting on your dSLR to its most optimal effect you can use color B&W filters. B&W filters will block certain wavelengths of visible light thereby enhancing the monochromatic look. For instance, the Red 25 blocks red spectrum that enhances visible blue, and your skies will be much deeper in their tonality. It's a good idea to experiment with these filters, as you can get exactly what you want in-camera without having to go to Photoshop.

The Soft Focus filter does exactly that, it reduces the sharpness of an image but only to the point that it's barely noticeable. These are used for portraits to soften and/or reduce lines and wrinkles.

Filters are a means to control the nature of light, so you can get the most from every image in the camera. Change your image by experimenting with filters.

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