Camera lens filters serve a variety of functions in digital photography. They’re most often used to capture scenery in difficult lighting conditions, enhance colors, and reduce reflections. Some photographers use lens filters simply to protect their camera’s lens. With a variety of filters to choose from it can be difficult to know which one to use in a particular situation. Today I’ll run through some of the basic types of lens filters and their common uses.
Lens filters are transparent or translucent glass elements you attach to the front of a lens that make slight, but noticeable changes to your image. They function as protection of your lens as well as altering the characteristics of light passing through the lens. Filters can be used to add special effects to an image, changing your image’s mood or tone. They attach to your camera’s lens in one of two ways — screw-in or slot-in.
Screw-in filters fit directly onto your lens by screwing onto the threads at the edge of the lens barrel. Each screw-in filter is a specific width, fitted to a particular lens size. Screw-in filters are great protection for your lens and make filters easy to swap in and out. Because they are fitted specifically to each lens you’ll need separate filters for each of your lenses.
Slot-in filters have a filter holder that is placed on the lens’ adapter ring, and the filters are dropped into the holder. The holder has interchangeable rings so the it can fit onto a variety of lens sizes. The lens holder typically has multiple grooves, so you can put more than one filter in at a time. The advantage of the slot-in filter is that you can stack filters, add or subtract filters quickly, and larger filters can work on smaller lenses.
Common Lens Filters
There are several types of lens filters to choose from. All alter the characteristic of light passing through the lens and give you different effects. Some of the most common lens filters are:
Polarizing filters reduce the amount of reflected light passing to your camera’s sensor. Just like polarized sunglasses, they darken skies, manage reflections, and suppress glare from shiny surfaces. Polarizing filters increase the contrast in landscapes by darkening overly light skies. They also reduce atmospheric haze and reflected sunlight. By rotating the filter, you can change the effect on the image. Polarizing lenses come in two varieties, linear and circular.
- Linear Polarizing lenses eliminate unwanted reflected light but will not work with the metering and auto-focus sensors in some DSLR cameras. This is because some cameras’ auto-focusing and metering systems are polarization-dependent.
- Circular polarizing lenses also eliminate unwanted reflected light, but work with most cameras because circular polarizing lens filters are only polarized in one direction.
UV or Haze Filters (sometimes called skylight filters) are transparent filters that block ultra-violet light and reduce haziness that is noticeable in some daylight photography, thus improving image quality. UV filters don’t affect most visible light, so they are great to use for lens protection without altering your exposure. There are however some ‘strong’ UV filters that can be used to cut atmospheric haze and reduce discolored edging that can occur with digital photography.
Neutral Density (ND) Filters are colorless or gray filters that vary the amount of sunlight entering the camera’s lens and allow the photographer to shoot at wider apertures in bright lighting conditions. This is particularly important in long exposure photography. On a very bright day there might be so much light that even at low ISO setting and minimum aperture, the slow shutter speed would overexpose the image. A neutral density filter allows you to achieve a shallower depth of field or motion blur of a subject in brighter weather conditions.
Graduated Neutral Density (GND) Filters The only difference between ND and GND filters is that only a portion of the GND filter is clear. This is used to compensate for the difference in lighting between landscape and sky. They can be very useful in high contrast landscape photography.
Color Filters (also called cooling or warming filters) correct colors and alter your camera’s white balance. They can block certain colors while allowing others through giving your image artistic effects. Most photographers use color filters for aesthetic or mood reasons, and they come in a variety of colors for different effects.
Other Types of Lens Filters
Soft Focus Filters intentionally blur the image slightly to smooth imperfections in in your image. They make a great tool for portrait photography and are sometimes called diffusion filters.
Black & White Filters To add a dramatic effect, B&W filters lighten similar colors and darken opposite colors. This gives your image a monochromatic look. There are a variety of colors such as Red, Orange, Yellow, Green and Blue filters for use in B&W photography that are all used to give different effects.
Close-up Filters are used primarily in macro photography They decrease the minimum focus distance of the lens and allow you to get up close to your subject without blurring.
Lens Filter Factor
Since a filter absorbs light, it requires an increase in exposure. Filter-makers usually suggest an amount of exposure compensation in the form of a “filter factor”. A filter factor of 2X means you should multiply the exposure by 2, 4X by 4, and so on. Each filter factor should correlate with 1 f-stop on your aperture setting. If your aperture is at its max setting you can also divide your ISO by the filter factor. If the filter factor is 2X and your ISO is 200, your new ISO would be 100.
Photographic filters are great for enhancing images and altering the mood or tone of your photographs. You can achieve many of the same effects by altering images in Photoshop but by using a filter you can immediately see the difference to your image in the viewfinder. With consistent practice and experimentation, you’ll find lens filters to be an indispensable tool for expanding your photography skills.