# Color Information ## OETF The Opto-Electronic Transfer Function (OETF) defines the relationship between the linear amount of light captured by the image sensor and the non-linear encoded value of each pixel. It is also referred to as "gamma", although many OETFs do not use a straightforward gamma exponent. Ember can capture in one of two OETFs: Rec. 709 and HLG Beta. Rec. 709 follows the standard [nonlinear encoding](https://en.wikipedia.org/wiki/Rec._709#Non-linear_encoding), with a gamma of approx. 2.2 - 2.4. HLG Beta is a custom OETF that boosts and flattens the tone curve slightly, pushing one more stop into the highlight range:
Although it can capture slightly more dynamic range and soften highlight roll-off in good lighting conditions, HLG Beta is still much closer to Rec. 709 than to a typical Log profile. The image sensor does not have enough native dynamic range to cover a Log OETF with acceptable shadow noise, a necessary tradeoff with high frame rates. Careful exposure is still necessary. When capturing with HLG Beta, shadow noise, including fixed-pattern noise (FPN) is also amplified. Depending on the lighting conditions, exposure, and amount of adjustment done in post, this may require the use of additional denoising steps. Davinci Resolve has several Spatial Noise Reduction options that are suitable, or there specialized tools like Topaz Video. ### 1D LUTs The following 1D LUTs convert between Ember's HLG Beta and Rec. 709 OETF. They operate on each color channel equally, adjusting only the Luma curve. {% file src="/files/cHZ8IM4i3R7JI14ZaZZO" %} {% file src="/files/3drI5p5j1R1HW4cftNbZ" %} ## Color Space Ember captures in an image sensor native RGB color space with a wider gamut than Rec. 709. So, out-of-camera colors will appear undersaturated without further adjustment. Below is an example of a color-matching workflow for Davinci Resolve for a clip captured in HLG Beta:

(All nodes disabled to show camera native color.)

(All nodes enabled to show corrected color.)

This workflow makes use of the two 1D LUTs provided above to move from HLG Beta into Rec. 709 for color matching, then to move back to HLG Beta. This allows for a more accurate color match in a known "gamma". If starting from a Rec. 709 OETF capture, the 1D LUTs can be omitted. The conversion back to HLG Beta can also be omitted or replaced with a different output curve or LUT. However, the front-end conversion from HLG Beta to Rec. 709 will decrease shadow and midtone exposure by about one stop. So, an output adjustment curve that takes this into account, boosting the low end back up to an acceptable noise threshold, might be desired. Consider this as a starting point, as more adjustments may be necessary for a specific scene. Once a suitable grade is achieved, the nodes can also be collapsed into a single 3D LUT that can be applied to other clips shot in similar conditions. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.freeflysystems.com/products/products/ember-camera/color-information.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.