Dynamic range and LUT’s

Let’s discuss Dynamic range and LUTs (Look Up Tables) and look at what happens when you import your captured data into an editing suite and then edit your captured footage. There are many fundamental considerations that must be respected.

A dynamic range is the range of tones in a scene, or within the captured data. Just consider it as the range of tones in whatever medium it applies to.

In the video editing workflow can be contained to four main areas.

1 – Dynamic Range of the Scene

The dynamic range of a scene being recorded  is dependent only upon the range of light and the subject contrast within the scene. A bright sunny day will be a scene with a high dynamic range as bright sunlight provides bright highlights and deep shadows.

The dynamic range of a scene under a thick clouded sky will be far less: highlights are not as bright and shadows are not as deep in comparison to the sunny day. On a studio shoot with artificial lighting, the dynamic range of the scene is governed by the lighting upon the scene.

Let’s make an indicative evaluation of some everyday examples.

Image Above: An everyday scene under cloud cover, a full cloudy overcast day and a bright sunny day.

You will notice the overcast day is the smallest dynamic range and the sunny day is the largest. Your camera should be able to record this data. Note – These examples do not apply to extreme lighting conditions.

2 – Dynamic Range of the Camera

The dynamic range of a camera can be described as the gamut, or the range of light that a camera can capture (record).

From the darkest tone (blacks) to the lightest tone (whites or highlights) a camera only has a set ability to record a range of these tones.  Professional cameras capture a far greater range of light  than amateur or pro-sumer cameras. Similar to audio recordings, from the quietest to loudest sound, both are what we call the dynamic range, or the ability of the recording device.

In the ideal world it would be perfect if the dynamic range of the scene exactly matched the dynamic range of the camera. This is rarely the case however.

In most situations the dynamic range of the scene is smaller than the camera’s ability and therefore it fits well within the capturing range of the camera.

If the dynamic range of the scene is larger than what your camera can capture, then you will lose information at one or both ends of the spectrum. You may lose highlight or shadow detail or both.

The dynamic range of the camera will just about always be smaller than the editing software dynamic range.

Which brings us to a third dynamic range.

3 – Dynamic range of Editing Software.

As all videos require some form of editing then the dynamic range of the editing software is paramount and is the aim of an accurate LUT.

Typically, professional editing software suites will have very large dynamic spaces. These are known as synthetic spaces and are governed by color spaces and codec technology. These are typically much larger dynamic spaces than what a camera can record.

The reason for this is simple. The larger the dynamic ability of an editing space, the greater expansion of tones and color and therefore, better quality of the final output.

4 – Output Dynamic Range

There is a fourth dynamic range in this equation and that is your output dynamic range. This can be online video spaces such as Vimeo and Youtube which are quite small, or the larger output spaces using codec spaces like Pro-res and so forth for cinematic reproduction. Fortunately, the same editing suite that provides that large editing space for editing your video, also has the ability to convert that data for output to multiple choices for viewing.

Of the four dynamic ranges in the workflow, we are mostly concerned with two: the dynamic range of the captured scene, and how the editing software suite changes that captured dynamic range via a LUT to fully fill and fit within its own dynamic range.

This is the role of an accurate LUT. A Lut will change and modify your captured data to fit into the dynamic range of the editing suite. If the LUT is accurate you will have the perfect data for editing. If the LUT is inaccurate then you will not have perfect editing data. Unfortunateley the majority of pre-packaged LUTs are not accurate at all.

An accurate LUT is vital for your editing and your output.

Confused yet? It’s okay if you are. If not, fantastic!

See below:

A Typical scenario above, where the captured data is smaller than the editing software’s range and ability.

From here, we apply a Look Up Table – LUT – to expand the captured date to the full range of the editing software.

When the LUT is applied, the dynamic range of the captured data and its color, is fully realised to fit into the software suites dynamic range.

NOTE – After the application of the LUT and depending which LUT you use, you may wish to refine and edit your footage further, or select a Specialised LUT that renders your footage as complete and final, and ready for output.

Tip – if the dynamic range of the original scene fits into the dynamic range of the camera then you are starting off very well. If the dynamic range of the scene exceeds the ability of the camera, then there is a risk of date being lost because it hasn’t been recorded.

Tip – Exposure – Accurate exposure is essential for superior quality outputs, but even with incorrect exposure we can still make great outputs, but always treat exposure of your original scene with the utmost respect.

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