When You Don’t Want to "Add It in Post," An Introduction to Optical Filters

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When looking to align camera images with what their eye sees, to smooth complexions subtly, or to create specific looks for various scenes, moods, or locations in their projects, experienced videographers and cinematographers often turn to optical filters. When you’re confident about the look you want, optical filters also enable you to “bake-in” elements of your vision, both saving time in post and reducing the possibility of unwanted or unintended “corrections.”

While many filter looks can indeed be replicated or at least approximated digitally in post-production, certain effects are best created while capturing your scene. Practiced on-set filter use can also reduce time and costs and avoid any additional noise created when applying digital effects during the editing process.

In general, while color-correcting in post is a vital creative process for many shooters, adjustments to parameters like contrast, reflections, diffusion, and flares are better handled while recording. The paths of light rays are physically tweaked as they pass through these glass filters, a process more difficult to achieve or simulate electronically than adjusting color, hue, and saturation.

Leading the Pack

Polarizers

Perhaps the one filter you must have in your kit, a polarizer is invaluable for seeing through glass reflections, reducing glare, producing saturated colors, and increasing contrast. Polarizers make clouds “pop” in landscapes and for wildlife documentary or fishing reality-show creators out there, they enable your camera to see beneath the surface reflections of rivers, bays, lakes, etc. This magic comes at the cost of one or more stops of exposure but then again, a polarizer can also do double duty as an ND filter when called for. Use a rectangular or square polarizer in a rotating filter stage or matte box or step up to the convenience of a rotating, round polarizer housed within a standard-sized rectangular filter frame. Circular polarizers use an additional layer to avoid the autofocus issues that can arise with linear polarizers and some DSLR or mirrorless cameras. The selective filtering of light rays achieved with the use of a polarizer is just not possible in post so make a “pola” one of your first filter selections.

See Through Reflections
Rotating Filter in 4 x 5.65” Frame

Neutral Density (ND) filters

Neutral Density (ND) filters darken your overall image, thereby requiring the use of a wider aperture and producing the resultant shallow depth of field, motion blur, and/or bokeh effects that you desire. Reach for higher-density ND filters when shooting on the beach, on snow-covered slopes, or anywhere you’d like to reduce high-intensity overall light. Horizontally or vertically graduated ND filters enable you to bring down a blown-out sky at the seashore or other bright location or to balance unevenly lit areas without underexposing your talent or objects in the other portions of the frame. IR NDs filter out infrared rays that may show up as color contamination on digital camera sensors, particularly with denser ND grades. Variable NDs are rotating filters that enable you to “dial-in” varying degrees of density; these round filters are a handy choice for drones or for DSLR/mirrorless shooters looking to save both time and weight in their setups.

Motion Blur with ND Filter
Horizontal ND Grad Filter

Diffusion filters

Diffusion filters like Tiffen's Black Pro-Mists and Schneider’s Hollywood Black Magics can be found on almost any professional television, movie, or commercial set featuring live actors. These filters subtly soften your picture by using embedded particles, threads, or indents to “defocus” tiny portions of the image while maintaining sharp overall focus and contrast. Use diffusion filters to reduce fine skin details on your talent and/or to create a more film-like, less stark look when shooting HD, 4K, or even higher-definition video. Fog and mist filters produce a similar though heavier effect, suitable for exterior shots.

Tiffen Diffusion Filters
Schneider Hollywood Black Magics

Some Filter Facts

Common pro-cine sizes include 4 x 5.65", 4 x 4", 138mm and Series 9 rounds; additional options include smaller sizes designed for drone and still-photography lenses. Filter “strengths” are usually defined in fractions and whole numbers, although a few lines, like Pancro’s Mitchell Diffusions, are labeled “A” through “E.”

Premium filters are constructed with finely polished and ground high-quality glass to provide even light transmission and consistent, accurate color reproduction. “Water white” glass and some manufacturers’ proprietary glass formulas reduce the green tint that may be seen in lower-quality glass filters.

Instead of stacking multiple filters, try combo filters to save space and set-up time; these are especially handy when balancing a drone or saving weight on stabilizers or handheld rigs. Combination filters include ND/diffusion pairs and various diffusion duos.

Additional Optical Filter Choices

Other popular optical filters include 812 or other Warming filters, Antique Suede, Chocolate, or other selections that can be used for the duration of a shoot or to lend a certain look to vintage flashbacks or select locations in your story. Color correction filters can match or correct ambient light or reduce the cast of sodium or mercury-vapor lights on exterior locations. When used properly, Day for Night filters cheat a nighttime look during the day, reducing tiring and costly overnight shoots.

Day for Night
Sunset Grad

Available in solid and graduated versions, Coral, Sunset, Blue, and Storm filters are used to customize the look of your exterior beauty or establishing shots. The grads provide a split field effect more easily than one can replicate in post-production.

Once you get your optical filter use started with a polarizer or add an ND for some shallow depth-of-field effects, you’ll want to explore others to customize your look throughout your shoot. Do you have a set of go-to filters? Share your thoughts below and explore the vast variety of optical filters on the B&H Photo website or drop by the B&H Photo SuperStore when you’re in New York City.

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