Updated: September 10, 2026
Two pieces of glass that change the picture
Most of what a filter does can be replicated in post. Two cannot, and both of them matter here more than almost anywhere else. A neutral density filter controls how much light reaches the sensor without touching colour. A polarizer controls reflections and the way the sky records. Neither effect can be added convincingly afterwards.
In South Florida, where the sun is high, the water is everywhere and the sky is a major part of most frames, these two filters do more for an exterior image than any amount of grading.
Why ND is not optional outdoors
Cinema cameras are usually run at a fixed shutter, around 1/48 of a second at 24 frames, because that is what produces motion that looks like film. Change it and movement either strobes or smears.
That fixed shutter is the problem. On a bright Miami afternoon, correct exposure at a low ISO with a normal shutter demands an aperture so small that the image loses the shallow focus everyone wanted, and diffraction begins to soften the picture.
ND filters solve it by cutting light before it reaches the sensor. You keep the shutter where it belongs, keep the aperture where the look requires, and simply remove the excess light. A midday exterior here routinely needs several stops of reduction, and shooting a fast lens wide open in full sun needs a great deal more than that.
Strengths are quoted in different systems, which causes confusion. Some are labelled by optical density, some by the number of stops, some by a fraction. Whichever your kit uses, learn one system and convert, rather than guessing on set.
The infrared problem
Heavy ND has a specific failure that catches people out. Strong filters block visible light effectively but let more infrared through in proportion, and digital sensors are sensitive to it. The result is a colour contamination that shows most in blacks and in synthetic fabrics, which turn a muddy red or magenta.
It appears at the strong end, typically past about six stops, exactly the range you need for a bright exterior. The fix is an IRND filter, which blocks infrared alongside visible light.
If your rental package includes plain ND above six stops, ask about the infrared behaviour before the shoot. Discovering a magenta cast on a black shirt in the grade is an expensive way to learn this, and it is not reliably correctable.
What a polarizer actually does
A circular polarizer cuts light that is reflecting off non-metallic surfaces. Rotate it and you change how much. Three effects follow, all of them useful here.
Water becomes transparent. Without a polarizer, the surface of the ocean or a pool is a sheet of glare. With one, you can see into it. For anything shot near water this is the single biggest improvement available.
Reflections in glass go away. Shooting through a window, a car windscreen or a storefront, the polarizer removes the reflection of whatever is behind camera, including the crew.
Skies deepen and foliage saturates. Blue sky records richer and clouds separate from it. Palm fronds and greenery lose their sheen and show actual colour.
The effect depends on the angle between the camera and the sun. It is strongest at roughly ninety degrees to the light and weakest when shooting directly toward or away from it. That has a practical consequence: on a shot that pans across a wide sky, the polarization will vary through the move and produce an uneven band. Either avoid the pan, or dial the filter back.
Using both together
A polarizer costs you light, usually around a stop and a half to two stops. That is convenient outdoors, because it means less ND is needed to reach the same exposure, which in turn reduces the infrared risk.
Stacking two filters brings its own considerations. More glass in front of the lens means more chance of flare and, on wide lenses, a risk of vignetting at the corners. Combination filters exist that put polarization and ND in a single piece of glass, which solves both problems at the cost of flexibility, since you can no longer change one without the other.
Whatever the combination, set the polarizer after framing, not before. Rotating it changes the image, so it has to be adjusted for the actual shot, and it needs rechecking every time the camera turns.
Screw-in or matte box
Screw-in filters thread onto the front of the lens. They are compact and cheap, and they need a matching size for every lens or a set of step-up rings. Changing them mid-setup is slow, and rotating a polarizer under a lens hood is awkward.
A matte box holds square or rectangular filters in trays in front of the lens. Filters swap in seconds, one size fits every lens, and a rotating tray makes polarizer adjustment straightforward. It also shades the front element, which matters in a place where the sun is often just outside the frame. The trade-off is bulk, weight and rental cost, and a matte box on a gimbal changes the balance considerably.
Variable ND filters, which adjust across a range by rotation, are convenient and worth knowing the limits of. At their strongest settings many produce an uneven cross pattern across the frame, particularly on wide lenses. They are excellent for run-and-gun work and less suited to controlled shots where the image has to be clean.
Filters that belong in post instead
Worth stating plainly, because filter kits are sold with a great deal in them that no longer earns its place on a digital shoot.
Colour correction and warming filters are unnecessary when you are recording in a wide gamut and grading afterwards. Graduated colour filters commit you to a decision that is better made later. Cheap diffusion and star effects are almost always regretted.
The exception is diffusion used deliberately for a look. Softening filters interact with highlights in a way that is genuinely difficult to reproduce in software, particularly on specular highlights and practical lights in frame. If that is the intended aesthetic, shooting it is better than adding it. Just be sure the client has seen a test, because it is not removable afterwards.
A graduated ND is the other one that still has a case. Holding back a bright sky while keeping a darker foreground exposed is a real problem on a Miami exterior, and doing it optically avoids the noise that lifting shadows in the grade introduces.
Practical habits on a Miami exterior
Keep filters clean and check them in the light before rolling. Salt spray and fingerprints on a filter degrade the image more than most people expect, and both are invisible until the sun hits them at an angle. Carry a proper cloth and a blower, not a shirt.
Watch for flare when the sun is low and to one side, which is when filter surfaces catch light. A flag or a French flag on the matte box solves most of it.
Finally, note your filter settings in the camera report. When the second unit shoots a matching angle two days later, or the edit needs a pickup, knowing that a shot was made with a specific ND and the polarizer at a particular rotation saves guesswork. That habit belongs with the rest of the on-set documentation covered in shooting in log and reading your monitoring tools.
We carry ND and polarizing filtration as standard on exterior work here, because in this climate it is not an accessory. You can read more technical articles on the blog, see how we work on the about page, or tell us about your shoot and we will spec the package around the locations.