Simple LUTs and ND filters can be a game changer. In particular, the best LUTs, built on our Shooting Standard, account for different shooting conditions and the color casts introduced by various ND (Neutral Density) filters. Here’s why:
Why Simple LUTs and ND Filters Work Together
Consistency Across Varied Conditions
Shooting conditions such as lighting, weather, and time of day can significantly impact how colors are captured on camera. LUTs tailored for specific conditions help standardise the look of footage, ensuring consistency across shots taken in different environments. By applying a LUT designed for a particular lighting scenario, you can quickly achieve a balanced color grade. Better still, it takes minimal manual adjustment.
Compensation for ND Filter Color Casts
ND filters are essential for controlling exposure, particularly in bright conditions. However, they can introduce color casts or tints that skew the colors of your footage. If your grade looks off, our guide on why your LUT looks bad can help. Different brands and models of ND filters can have distinct color biases, such as a greenish or magenta hue. Simple LUTs designed with these specific color shifts in mind can neutralise unwanted tints, restoring accurate colors to your footage. Since each ND filter brand may introduce a unique color cast, brand-specific LUTs save time in post-production. In effect, you apply a LUT calibrated to counteract known color issues.
Simplified Workflow
Using LUTs that account for both shooting conditions and ND filter effects streamlines the color grading process. Instead of starting from scratch or making numerous adjustments, you can apply a LUT that brings you close to your desired look immediately. This efficiency is especially valuable in fast-paced environments where quick turnaround times are essential. Even with simplified LUTs, you retain the flexibility to tweak and refine the grade. As a result, you focus on creative choices rather than technical corrections.
Improved Image Quality
By using LUTs designed for your exact conditions and filters, you preserve more of the camera’s dynamic range and color accuracy. These LUTs are optimised to correct issues without overcompensating, which can occur with generic LUTs. For projects that require a cohesive look, such as a series of videos or a feature film, LUTs designed for specific conditions and filters ensure that the aesthetic remains consistent throughout, enhancing the overall production value.
Simple LUTs are designed around specific shooting conditions and ND filter brands. Therefore, they address common grading challenges like varying light and filter-induced color casts. They also make post-production faster, more efficient, and more consistent. Ultimately, creators focus more on the artistic side of filmmaking.
Why Color Casts Vary Between Different ND Filter Brands
Color casts vary between ND (Neutral Density) filter brands for several reasons. Specifically, they stem from differences in materials, coatings, and manufacturing:
Material Quality and Composition
ND filters can be made from optical glass or resin, affecting how light passes through the filter. Lower-quality materials might not block all wavelengths uniformly, leading to color casts. High-quality glass often features multiple coating layers to reduce reflections and ensure uniform light transmission. Lower-end filters may lack these coatings, resulting in color shifts.
Coatings and Anti-Reflective Layers
Premium ND filters often use multi-coating layers to minimise color shifts. By contrast, filters with fewer or no coatings can introduce tints. UV and Infrared (IR) cut coatings prevent color contamination from these wavelengths, which can cause shifts, especially in digital sensors. Filters without these coatings might introduce color casts in shadows or highlights.
Manufacturing Precision
Uniformity and thickness of an ND filter are crucial for consistent color. Even slight variations in thickness can lead to uneven light blocking and color casts. High-end filters are manufactured with strict tolerances to ensure consistent performance, whereas lower-end filters may have less precise manufacturing processes.
Neutrality of the Filter
An ND filter should block light evenly across all wavelengths to be “neutral,” but achieving true neutrality is challenging. Filters that are not neutral may block some colors more than others, leading to color casts. Different brands prioritize various aspects of filter design, affecting their color neutrality.
Filter Strength
Higher-density filters (6-stop, 10-stop) block more light. As a result, they carry a higher risk of color shifts that exacerbate any imbalances. Some brands manage this better than others depending on their design and manufacturing processes.
Conclusion
Color cast variations between ND filter brands arise from differences in materials, coatings, manufacturing precision, and neutrality. Higher-end filters typically offer better color neutrality thanks to advanced materials and coatings. Meanwhile, lower-end options may introduce color shifts that need correction in post.
Using ND Filters When Filming in Log Profiles
ND filters help when filming in a Log profile, such as on an iPhone 15 Pro. In practice, they maintain optimal shutter speed, deliver cinematic motion blur, and control exposure across lighting conditions. Here’s a guide to using ND filters from ND4 to ND64:
ND4 (2 Stops)
Ideal for overcast or cloudy days where the light is soft and diffused but still bright enough to require reduction. It’s also perfect for golden hour when the light is gentle. ND4 helps maintain your shutter speed at the ideal 1/48 or 1/50 for 24fps.
ND8 (3 Stops)
Suitable for bright overcast conditions where the sun is diffused by thin clouds. It’s also helpful for indoor scenes with large windows letting in significant light. ND8 helps balance indoor lighting with the bright outdoor environment.
ND16 (4 Stops)
Best for sunny days with bright but indirect sunlight. ND16 reduces light to maintain proper exposure while preserving the desired shallow depth of field and cinematic motion blur. It’s also useful in bright cloudy conditions.
ND32 (5 Stops)
Ideal for bright sunlight or intense conditions, such as midday sun or wide-open spaces. ND32 helps maintain proper exposure without closing down the aperture too much. It’s also effective in desert environments or areas with intense light.
ND64 (6 Stops)
Best for extremely bright, sunny conditions or scenarios with overwhelming light, such as reflections off water or metal surfaces. ND64 helps keep your Log profile’s dynamic range without overexposing.
General Tips
In bright conditions, use ND filters to follow the 180-degree shutter rule, where shutter speed is double the frame rate. This maintains natural motion blur. For the wider theory, see our insider’s guide to LUTs. ND filters help avoid excessively high apertures and control exposure. When shooting in Log, avoid overexposure as blown-out highlights are hard to recover. Select the appropriate ND filter to achieve optimal exposure, maintain dynamic range, and create professional-quality footage in any lighting condition.
For some brands, like Polar Pro on a GoPro or DJI Osmo 3, which only offer ND8, ND32, and ND128, adjust your ISO accordingly. For instance, with ND128, set your ISO to double the lowest value (e.g., ISO 100 to ISO 200) to match an ND64 effect. For brands like Freewell, which offer dedicated ND filters for each stop, you can use the specific filter for each stop.
Do some tests and use appropriate meters to gain insight. It will become second nature with practice. For variable ND filters, adjust until you achieve perfect exposure, keeping in mind frame rate adjustments. Experiment, and then use your Simple LUTs to simplify the entire process.