Before computers and digital cameras, lens filters were among the indispensable tools filling every serious photographer’s bag. Fast forward to the present and the first things that come to many minds when they hear the words “photo filter” are overused color profiles and distorted selfies on social media. Today, editing software can simulate the effect of many types of lens filters, reducing the need for photographers to invest in and carry around entire collections of additional glass. However, there are still a number of filters that cannot be recreated easily (or at all) with a computer. That is the topic of this article.
Polarizing Filters
Polarizing filters remain essential accessories for just about every photographer. Two types of polarizers exist: linear and circular. Both reduce reflections, boost saturation, and darken blue skies. The most unique of these attributes is the ability to cut down on non-metallic reflections, making it easier to shoot through windows or beneath water surfaces without distracting glare. This ability cannot be added back into an image on a computer.
Circular polarizers are linear polarizers that have been updated to include a quarter wave plate. Why does that matter? A quarter wave plate prevents cross-polarization, a phenomenon that disrupts autofocus systems and can darken images when using an SLR camera. Note that polarizing filters require increasing your exposure by approximately 1.5-2 stops. For a more thorough discussion of circular polarizers, check out Shawn Steiner’s article here.
Neutral Density Filters
An equally popular filter, especially with landscape photographers and cinematographers, is the neutral density (ND) filter. The function of an ND filter is to reduce the amount of light that passes through your lens while leaving image color untouched (hence, neutral). This allows you to extend the time of image capture while avoiding overexposure. If you’ve ever seen a photograph wherein moving water or clouds have been smoothed into abstract passages of color, you’ve witnessed the work of an ND filter. They also serve a critical function blocking light for cinematographers working in bright environments while using slow shutter speeds.
ND filters vary in strength, depending upon how much light you need to block. For a thorough discussion of the nomenclature, (e.g. optical density numbers, ND filter factor numbers) read Todd Vorenkamp’s article here. In broad terms, as the numbers increase, the strength of filtration also increases. The two most common types of ND filters are solid and variable. Solid ND filters offer a specific strength while variable ND filters can be rotated to provide a range of effects. For more specialized applications, graduated ND filters vary the degree of density across an image field, ideal for managing bright skies while center ND filters are designed to balance exposures when used with extremely wide-angle lenses.
Solar Filters
The sun is one of the most difficult and dangerous objects to photograph. Never point a camera at the sun without proper filtration and even when using proper filtration, never look through an optical viewfinder. Solar filters are essentially very powerful neutral density filters combined with added UV and IR filtration capabilities. As you can imagine, they block a lot of light: between 16 and 20 stops depending on the model. This allows you to acquire detail of our closest star that would otherwise be blasted into highlight oblivion. To learn more about how to photograph the sun, check out Todd Vorenkamp’s article here.
Light Pollution Reduction Filters
Since we are on the topic of outer space, city-dwellers such as me are swaddled by ambient light day and night. This becomes a problem when trying to capture compelling images of the night sky. Light pollution reduction filters address this issue by absorbing wavelengths of light common for artificial light. The problem is that light pollution comes in a variety of forms. Depending on the model of filter, you may be able to cut back light from sodium-vapor, mercury-vapor, low CRI LEDs, or infrared pollution. While astrophotographers are often quite adept at post-processing their images, by reducing excess, unwanted light during capture, your camera will be able to capture detail that may otherwise be lost. You can find an extensive review of light pollution reduction filters here.
Close-Up Filters
Technically lenses but often categorized with filters, close-up filters reduce the minimum focusing distance required to capture a subject. Think of them as reading eyeglasses for your camera. Varying in dioptric strength, they serve as a cost-effective means of approximating the capabilities of a macro lens. Likewise, they can be used on telephoto lenses to capture small, skittish subjects up close while maintaining greater distance than with a macro lens would permit.
Clear Filters
The last filter to make this list is arguably the most underappreciated: the clear filter. Designed to have no effect on your image, why would it be included here? For the countless lenses that it has spared from drops, scratches, and other acts of destruction. You can’t fix a damaged or non-functioning lens in post. For many, UV filters serve as a similar role as an “everyday” filter—with the added bonus of blocking UV light. While you may be reluctant to shell out significant money on a filter with little noticeable effect, it is important to remember that anything that you put between your lens and the world has the potential to alter or distort images. Always choose filters of high quality to ensure that you are not compromising the sharpness or accuracy of your lens by putting something sub-par in front of it.
Which of these filters are in your camera bag? Are there any that didn’t make the list that you can’t live without? Let us know in the Comments section, below.
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