Exposure Guide
Make sure to use the latest Camera Firmware and Wave Player, available on the Downloads page, as continuous improvements to the color processing pipeline are made. In v1.1.0 Camera Firmware, highlight handling was improved, providing approximately a half-stop more dynamic range. This was done by allowing some sensor clipping and using the unclipped channels to recover highlight detail, aided by a smoother highlight desaturation curve. In v1.4.0 Wave Player (Windows) software, the ability to create User Calibrations was added to further reduce the presence of Fixed Pattern Noise (FPN), which extends the dynamic range further, especially in underexposed conditions.
Shooting high speed video requires a lot of light. Each frame has less time to capture light, so more photons are required. The Wave camera's native ISO is 250. To get a feel for how much light is required at a given frame rate, you can compare with another camera using equivalent ISO and Shutter Speed settings:
Wave Settings | Comparable ISO and Shutter Speed |
4K, 420fps, 180º | ISO 250, (1/840)s |
2K, 1440fps, 180º | ISO 250, (1/2880)s |
To maximize frame rate, Wave captures in 10-bit linear with minimal processing and noise reduction. This is much different than a cinema camera that captures in 14-bit or 16-bit linear and processes the HDR image down to 10-bit log, with significant amounts of on-board noise reduction. As a result:
- The dynamic range is 10-11 stops, vs 14+ stops for a cinema camera.
- More careful control of lighting is needed to fit the scene’s dynamic range to the sensor’s. The image is less forgiving to under/over-exposure.
- Additional tone curve adjustment and noise reduction in post can be used. For example, the Shadows adjustment in Wave Player can help curve out shadow noise.
Black level in high-contrast scenes will be lower than black level in low-contrast scenes. This also has implications for the noise floor.
Contrast-Dependent Black Level and Noise Floor
If a scene is under-exposed, the black level and noise floor will be higher. Additionally, tone curve adjustment and noise reduction will be less effective, since more of the scene's information is in shadows. The noise can't be reduced without also throwing out information.
Magenta-tinted shadows are also a consequence of the artificially higher black level in underexposed scenes: too much color correction is applied to the higher shadow levels. To compensate for this, the black level can be manually adjusted downward in Wave Player, or the Shadow Rolloff setting can be adjusted to reduce shadow saturation.
Wave works well for indoor studio and tabletop shooting, as it’s usually much easier to control the lighting. You do need a lot of light, though. Set exposure to exactly fill the histogram with highlights just below 100% (other than light sources and specular). Then add light as-needed to fill shadows.
- Dark, flat backgrounds will exaggerate the noise. If you want a black background, be prepared to use the Shadows curve adjustment to suppress noise. Add extra fill light to shadowed areas on the foreground/subject to compensate.
- Light or textured backgrounds work well as-is without much adjustment.
- Outdoor light from windows in the background will probably clip. If you need to also capture what’s outside the window, follow the Outdoor tips.
There’s plenty of light outdoors, but fitting an outdoor scene into the available dynamic range is more challenging. More discretion and test shooting might be required to know if Wave will work for a given outdoor shoot. Use a daylight-visible field monitor and hood to make sure you can get a good look at the preview image exposure.
When possible, keep the sun behind you. This will reduce the scene dynamic range by illuminating the subject more, allowing more of the background to also be captured.
If the scene has to be backlit, it will probably have more dynamic range than can be captured by the sensor. You have some choices:
- Add some fill lighting or bounce some sunlight onto the subject.
- Expose for the subject and allow the sky to clip.
- Expose for the sky, allowing the subject to be in silhouette.
Last modified 1yr ago