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HDR Light Studio - Documentation

opencolorio

HDR Light Studio uses OpenColorIO color management. OCIO provides a straightforward and consistent user experience across all supporting applications while allowing for sophisticated back-end configuration options suitable for high-end production usage.

OpenColorIO is simple to use in HDR Light Studio, and is automatically configured and ready to use after installing HDR Light Studio.

 
There are 3 areas in HDR Light Studio where Color Management is used:

1. Display
All content inside HDR Light Studio is handled in linear format - i.e. no color transform = ground truth values. For example, the Render View, Light Preview and Canvas are all displaying linear image data. So, in order for them to look correct on your display, a display LUT/Color Profile needs applying to this data. The most popular LUT to use for your display is sRGB. We suggest using the Preferences to set your default OCIO Default View to sRGB.

view_luts_compare

2. Loaded Images
Anywhere where an image can be loaded into HDR Light Studio, a Color Profile can be set for the image. This Color Profile tells HDR Light Studio the color profile that is embedded in the values of the image, so it can convert the image back into linear color space. Therefore when selecting sRGB for example, the image has a 'reverse' transform of the sRGB profile applied. It does not apply another sRGB transform, this would result in the image having a double sRGB profile applied.

Below a photograph has been loaded into HDR Light Studio, it is a JPEG file and will be in the sRGB color space. By default a Color Profile of Linear is applied to loaded images. The image on the left looks washed out, it needs to be set to sRGB in order to remove it's sRGB color space, and return the image to linear space. Then when the image is displayed in the Light Preview, which has an sRGB color space, the image appears correctly.

loaded image lut compare

3. Production Render
When producing production renders of your HDR content. There is an option to set a Color Profile for the output. It is very rare you would want to use this as it would destroy the integrity and lighting look you had created in HDR LIght Studio. But it does allow a Color Profile to be used perhaps to change the lighting look to a specific feel.

 

A Recommended Simple Color Workflow

For some 3D artists color management can be a little daunting and confusing.

Here are some simple rules if you want to use the color management in the most simple way:

1. In the application Preferences, set OCIO Config to nuke-default, and OCIO Default View to sRGB (default) this means at all times when starting HDR Light Studio, the Canvas, Render View and Light Preview will display their image content with sRGB profile.

2. When loading high dynamic range images into HDR LIght Studio, leave the Color Profile set to : Linear. This assumes the HDR file is already in linear color space, which it should be.

3. When loading any LDR image (say a standard photograph as a JPEG) change the Color Profile for that image to sRGB, this will then transform that image to linear space.

4. When rendering your final output, leave the Color Profile in the Production Render as Linear, so all output content is linear. This is what is needed for accurate lighting in your 3D software.

 

Customizing OCIO

In a larger studio, the OCIO environment variable allows you to specify your OCIO config file. Here's an example pointing to some Nuke defaults that ship with HDR Light Studio:

OCIO = C:\Program Files\Lightmap\HDR Light Studio\OCIOConfigs\nuke-default\config.ocio

This value can been seen (if set) in the Preferences dialog. For further information see http://opencolorio.org/

 

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