A camera lens filter is a commonly used photography and cinematography accessory. While lens filters initially served a singular purpose – to filter out ultraviolet light – modern filters serve a diverse range of applications. We’ve broken down everything you need to know, including the different types of filters and when and where to use them.
What is a Lens Filter?
Different filters yield different effects. However, the primary purpose of all lens filters is to alter the transmission of light through the lens.
Technically speaking, light is a type of electromagnetic radiation. Electromagnetic radiation travels in waves of varying frequencies, spanning a range called the electromagnetic spectrum.
The distance between waves (called a wavelength) at certain points along the spectrum indicates different types of radiation. For example, visible light wavelengths are typically between 400 and 700 nanometers. Other types of light, such as ultraviolet (UV) and infrared (IR), have shorter and longer wavelengths respectively.
In the early days of photography, it was discovered that film was sensitive to UV light. While imperceptible to the human eye, UV light would add haziness to photos captured on black & white film, and a blueish hue to color film photos. To combat these effects, filters made of transparent materials such as glass and resin were designed to cover the front of lenses and prevent light with UV wavelengths from entering the camera and being exposed to the film.
Nowadays, UV filters are less critical. Film stock is created with less sensitivity, digital cameras have UV-filtration built into their sensors, and modern lenses feature front element coatings that also filter UV light. Not to mention the wondrous things that can be done to an image using editing software like Lightroom.
UV filters are still used, though primarily as a means of protecting the lens, rather than for the purposes of light filtration. Other types of lens filters have also been developed and are regularly utilized by amateur and professional photographers and filmmakers. These include polarizing filters, neutral density filters, color filters, light pollution filters, and others.
Lens Filter Size & Quality
Different types of filters serve different applications. We’ve broken them down below, but first, let’s review a few things to keep in mind before you buy.
We recommend strictly investing in high quality lens filters. Because the filter is placed over your lens, there is a significant risk of image interference. A poor-quality lens filter, regardless of type, may incidentally cause lens flare or image distortion.
Reputable filter brands such as NiSi exclusively use high quality optical glass for their filters. This ensures the filter acts like an extension of your lens rather than a shield, reducing the risk of distortion or flare. With a standard thickness of just 2mm, their photography filters also pose less chance of vignetting or reducing sharpness. Additionally, all their filters feature a coating that keep reflectivity low and make them easier to clean.
Lenses come in different shapes and sizes, so lens filters do too. There are circular filters that screw onto the lens, as well as square and rectangular filters that require an external holder to mount them to the lens.
Most lenses have a filter thread around the circumference of their front element, allowing circular filters with the same diameter to be screwed on and attached. You may have noticed ‘filter size’ as a technical specification listed in the marketing material for most lenses. For example, the Sony 24-70mm F/2.8 GM filter size is 82mm. This means it should only be fitted with 82mm lens filters.
The most common circular filter sizes are 49mm, 55mm, 62mm, 67mm, 72mm, 77mm, and 82mm. However, these are certainly not the only options. Given the variation in lens size and shape, if you own multiple lenses, it’s likely you will require filters of multiple different sizes.
Lens Filter Types
While new kinds of filters are still being developed, we’ve broken down seven of the most common lens filters below.
The OG lens filter, designed to prevent ultraviolet wavelengths from entering your lens. While you may still find it beneficial to use a UV filter if you shoot on film, digital sensors and modern lens coatings have essentially negated UV filters. Today, UV filters are primarily used as a means of protecting your lens (see protection filters below).
UV filters should not be confused with UV Pass filters, which serve the opposite purpose. They permit UV light rays to enter the lens, while blocking visible and infrared light, in order to produce uniquely colored imagery. An IR pass filter offers the same function, but for infrared light.
Protection filters are exactly what they sound like. They’re designed to protect your lens from scratches, fingerprints, water, dust, sand, and other contaminants they may be exposed to while in use. While many photographers use UV filters, there are protection filters that don’t filter the light, strictly serving as a barrier between your lens and the world.
There is rigorous debate in the photography community over the usefulness of protection filters. Some argue the risk to image quality isn’t worth the protection the filter offers. Others counter that only inferior lens filters disrupt image quality, while a high quality protection filter prevents permanent damage, another threat to overall image quality.
Some photographers prefer to use a lens hood to protect their lens without the risk of distortion or flare. However, a lens hood cannot protect the lens from contaminants the same way a protection filter can.
Ultimately, it’s a question of personal preference. While using a lens filter can impact the quality of your imagery, investing in a high quality brand like NiSi greatly mitigates the risk of distortion and lens flare.
Images captured with and without a NiSi CPL circular polarizing filter | Courtesy of NiSi
Polarizing lens filters are the most used filters after UV/protection filters. Particularly popular with landscape photographers, they serve three key purposes: to reduce lens flare, increase color saturation, and remove reflection from non-metallic surfaces.
Let’s briefly breakdown how a polarizing filter works. Light travels in all directions. When waves of light hit a flat, reflective surface, they tend to reflect in a single, concentrated direction, producing a glare effect. For example, imagine a lake on a bright day. The water is reflecting a harsh, white light that’s hard to look at. This is polarized light.
A polarizer filter features a layer of gel sandwiched between two layers of glass. The nanostructure of the gel allows it to absorb light flowing in a specific direction, while enabling other light to enter the lens. Rotating the filter allows you to dictate what angle of light is absorbed. The result is that instead of seeing a harsh glare on our hypothetical lake, when viewed through a polarizer filter at the correct angle, the lake would appear as it’s natural, blue color.
The unique filtration of a polarizer translates to enhanced image quality, especially when photographing outdoors. There’s less risk of lens flare, colors are more vivid and saturated, and non-metallic surfaces display their natural tones instead of reflective glare. These effects are hard to produce after the fact using editing software, which is why polarizing filters remain a popular accessory for photographers.
The color tone of a polarized image generally leans a little warm, though this varies depending on the brand and filter you use. For example, NiSi manufactures multiple types of circular polarizer filters, including a polarizer optimized for landscape photography and a true color neutral polarizer.
Neutral Density Filters
Neutral density filters block light traveling in all directions from entering the lens. ND filters come in a range of intensities, depending on how much light you want to prevent from entering your lens.
Photographers typically control how much light enters the lens using the aperture, ISO, and shutter speed settings on their camera – also known as the exposure triangle. However, in harsh light conditions, it can be hard to find the perfect equilibrium between the three settings to produce a high quality image. A ND filter provides photographers with a fourth means of controlling the exposure.
For example, imagine a portrait photographer taking photos outside on a sunny day. They want a sharp, close-up shot of their subject’s face with a creamy, bokeh-filled background. The easiest way to generate this effect is to use a wide aperture, such as f/2.8. However, because it’s bright outside, a f/2.8 aperture would allow too much light to enter the lens, resulting in an over-exposed photograph.
When utilizing a ND filter, less light will enter the lens. This allows the photographer to use a wide aperture and achieve their intended effect. Similarly, when shooting a long exposure photograph, which requires a slow shutter speed, a ND filter again allows less light to enter the lens, preventing an over-exposed image.
The density of the filter is measured in stops, and dictates how much light enters the lens. For example, a 10-stop filter blocks more light than a 6-stop filter. Variable ND filters offer a range of light control stops, adjusted by rotating the filter.
Graduated Neutral Density Filter
A graduated neutral density filter offers a partial light filtration. The density varies over the area of the filter. This allows you to block light from a specific portion of your frame.
For example, imagine photographing the beach on a clear day with the sun in frame. The sun will emanate a bright, uneven amount of light in your image. Adjusting your exposure settings to reduce the brightness of the sun will make the ocean and beach look dark. Alternatively, adjusting the settings for a nice shot of the beach means the sun casts a bright, distracting light at the top of the image.
Utilizing a graduated ND filter allows you to maintain optimal settings for a photo of the beach, while diluting enough of the sun’s light that it doesn’t disrupt the rest of the image.
Graduated ND filters come in multiple variations. For example, NiSi offers four different graduations for their rectangular Nano IR GND filter: hard, medium, soft, and reverse. The reverse filter offers a clear top and bottom, and dense middle.
Color lens filters are an easy way to add a unique color profile to your photos before you even hit the shutter. While color grading can also be done quite effectively in post-production, a color filter arguably produces a more natural tone. Of course, the downside is that you’re somewhat locked into the color you choose.
Color filters are also used for black & white photography, which might sound contradictory. However, utilizing a color filter alters the tone of certain colors, helping them to stand out from similar colors once the photo is in black & white. For example, an orange color filter brings out red and yellowish hues. When utilized for a black & white portrait, it will make your subject’s skin look brighter and smoother, especially if contrasted with a dark or cool colored background.
Light Pollution Filters
Photos by Brendan van Son | Courtesy of NiSi
You guessed it; light pollution filters filter out light pollution. If you’re wondering what that looks like in a photograph, it’s the hazy, smog-like quality you may have seen in photos of a skyline or urban area taken at night. Additionally, it also reduces clarity in photos of the night sky, aka astrophotography.
Light pollution filters like the NiSi Natural Night filter are specifically designed to filter out wavelengths from common sources of light pollution, such as streetlamps. The end result is clearer imagery with stronger contrast and definition.
Square & Rectangular Filters
While most photographers opt to use circular filters that screw on to their lens, square and rectangular-shaped filters are also available. They are typically attached to the lens using a holder that mounts on the front of the lens, like the NiSi P49 for lenses with a 49mm thread size.
Square and rectangular filters are arguably more versatile. Using low-cost adaptor rings, you can mount the holder (and thus, all your square filters) to multiple lenses with varying filter thread sizes. Additionally, holders like the NiSi P49 can stack multiple filters for simultaneous use.
Square filters are also well suited for use with ultra-wide-angle lenses. The front element of these lenses is often quite curved, resulting in vignetting when used with a circular filter. A square lens extends fully over the edges of the front element, reducing this risk.
Special Effect Filters
There are numerous other types of lens filters that can be used to control how light flows through your lens into the camera. This includes filters that can diffuse the light to produce a cinematic, halation effect.
The Unfiltered Truth
Lens filters are an important accessory for photographers, videographers, and cinematographers. Just like cameras and lenses, you get what you pay for. A low-cost, low-quality lens filter can have detrimental effects on your photos, while professional-grade filters produced by brands like NiSi can be used effectively to enhance your imagery.
We hope this guide has given you an idea of the different types of filters available, and the circumstances and styles that demand their use. If you still have questions about lens filters, let us know in the comments below.