Free Look LUTs
Using the standard capabilities of LightSpace CMS Light Illusion has generated a selection of three 'Look LUTs' that can be downloaded for free using the below contact form.
The LUTs include Film Emulation for Log and TV Legal images, as well as one for use with ARRI Log footage.
The three Look LUTs are for use in a Rec709 workflow, and are as follows:
- Film Look for Log footage
- Film Look for TV Legal footage
- ARRI Log Look LUT based on ACES data
And come in a package of formats that can be used in many different grading and graphics systems, as well as a a range of displays and LUT boxes.
- ARRI .3dl
- Scratch .3dl
- Autodesk .3dl
- Flame .3dl
- Lustre .3dl
- Smoke .3dl
- Resolve .cube
- FSI .dat
- Mistika .itx
- Nucoda .cms
- Nuke .3dl
- Quantel .txt
- Sony .lut
- TVlogic .lut
Look LUT Generation
The following describes the process used in generating these three Look LUTs using just the in-built LightSpace CMS tools.
Film Look LUT for Log footage
The first Look LUT is a fairly simple one to generate, as it is based on the in-built 'Kodak Vision' film stock data, and the basic operation is to simply build a LUT with 'Kodak Vision' as the Source colour space, and Rec709 as the Destination.
Using the default Rec709 White colour space values (0.3127x, 0.3290y) results in a LUT that has the film's warmer white point and grey scale burnt into it. This is as is needed for true Film Emulation LUT generation, but is not what we want for this Look LUT, as we want to maintain the standard cooler D65 white point of video, but with the 'feel' of the film's contrast and colourimetry.
So, we will alter the Destination White coordinates to better match the film's warmer white, which will result in a LUT that maintains the standard video D65 white and neutral grey scale, as the LUT will not be changing the colour temperature.
With the Rec709 White xy values changed to 'warmer' film projection values the result is a LUT that is not altering the video white point. Here we have used 0.3400x and 0.3500y, which is close to getting an unaltered white point. Close is good enough as film has a grey scale that is not the same colour temperature through it range, as can be seen in the above 1D graph where the grey scale is warmer in the high grey values, and cooler in the lower values, so will need to deal with that separately.
As we really want a neutral grey scale we will use the LUT Manipulation filters to remove the film based colour tint contamination.
The LUT Manipulation Filter to be used is 'Axis Blend', set to effect the full Grey Scale range, with the default 'Blend' setting.
(See the LightSpace CMS LUT Management User Manual for more information on LUT Manipulation tools.)
Axis Blend for Neutral Grey Scale
As the Convert Colour Space xy values used were 'approximate' there is a small reduction in the Peak White value of the LUT, as can be seen by the 1D curve plot not quite reaching the top of the graph. So, we will use the 'Gain' LUT manipulation option to very slightly increase the peak white value.
Note the use of 'Append'. This is needed to apply the Gain 'after' the LUT, rather than 'before', as before would lift the body of the LUT, but NOT the Peak White value.
Gain Adjustment For Peak White
The Film Look LUT for Log images is basically now complete, and can be exported in the required LUT format.
However, there are additional adjustments that can be made...
Looking that the 1D Graph the LUT profiles can be seen to be slightly 'irregular', which is correct as the LUT is based on true film density measurements, and that is the nature of film. So, a 'Smooth' LUT Manipulation Filter can be use to remove the irregularities.
Smoothing LUT Irregularities
The 'Smooth' process introduces some colour temperature tint back into the grey scale as the LUT does not contain even colour distribution throughout, obviously, so the 'Axis Blend' filter can be applied again to re-normalise the grey scale, with the 'Smoother' profile.
Axis Blend for Neutral Grey Scale
The LUT is now complete, and can be used as a Look LUT for grading work. As with all Look LUTs the LUT should be applied at the end of the image path, with grading performed 'under' the LUT.
Film Look LUT for TV Legal footage
For use with TV Legal images the above LUT needs to be converted to expect image that are Rec709 TV Legal range.
There are different approaches to this, with the most obvious being to use the LUT Manipulation 'Prepend Log->Vid' process. However, this conversion is 'technically' accurate, which is not what we always want, and in this case is not what we want...
For this conversion we want a LUT that 'looks' better on TV Legal images, rather than just being a Log to TV Legal conversion, so we are going to be a bit more 'creative' in the conversion process.
The first thing to realise is what we 'really' need to do is remove most of the log based Contrast change, as TV Legal material already has the maximum 'contrast' available to it, but we also need to keep a 'bit' of the film contrast Look & Feel.
With this in mind, the first step is to 'Invert' the contrast component of the Film Log LUT, so that the inverted data can be 'subtracted' for the Log Film Look LUT. And the first step is to convert the 3D LUT into a 1D LUT, so only the contrast data is contained within the LUT, and no colourimetry data.
Using 'LUT Manipulation/Filters/Grey Blend' will convert the 3D LUT into a 1D LUT. With the LUT converted into a 1D format all the colourimetry data is stripped out, leaving just the contrast information.
This 1D LUT can then be inverted using 'LUT Manipulation/Invert'.
If we now 'Add' the original Film Look LUT for Log image to this inverted 1D LUT the result would be a LUT with no contrast alteration at all, but all the 'film colourimetry', which may be what you want...