Look LUTs Design

LightSpace CMS workflow used for the downloadable Look LUTs

This page defines the LightSpace CMS workflows used to develop the downloadable Look LUTs.

The LUTs include True Film Emulation for Cineon/Log C & TV Legal Rec709 images, as well as an additional LUT generated via ACES data, also for Log C images.

Looks LUTs

Film Emulation LUT Generation

The following describes the process used in generating true Film Emulation LUTs, using just the in-built LightSpace CMS tools and available pre-set film profile data also provided within LightSpace.

This means the LUTs are true Film Emulation LUTs, generated with true film spectral data, and not simple Look LUTs.

Film profiling is a service performed by Light Illusion and has been used by many of the world's top film studios, film labs, and post facilities when performing film based post-production workflows.

True Film Emulation

It is worth pointing out that the three film profiles built into LightSpace CMS - Kodak Vision 2383, Kodak Premier 2393, and Fuji Super F-CP 3510 - are based on real film colourimetry data, measured from the specific film stocks, using Light Illusion's highly accurate hybrid spectrophotometer & densitometer combined with an extremely stable and fully automated stepper motor controlled film transport system.

Both are Light Illusion developed systems that have provided the majority of the film emulation data used by the world's leading studios, film labs, post-production facilities, and those providing genuine film emulation LUTs, such as Koji.

Contact Light Illusion directly for more information.

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.

Default Values
Film 'Warm' White Point

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.

Warm White Values
Video 'D65' White Point

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 throughout its 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, and we 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
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
Raised 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. But, a 'Smooth' LUT Manipulation Filter can be used to remove these irregularities.

Smoothing LUT Irregularities
Smooth LUT

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
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 is best applied at the end of the image path, with grading performed 'under' the LUT.

Marcie Log Image
Marcie LUT Applied

True Film Emulation vs. Guesstimation

What does 'True Film Emulation' really mean?

In very simple terms, true film emulation LUTs are based on spectral data extracted from real film stocks using a spectrophotometer based system, as with the Light Illusion Film Profiling Service. Alternative, inferior, film look LUTs are often based on visual image matching, attempting to mimic the look of film without the use of any true film spectral data.

This means is that such LUTs do not contain any of the film's natural non-linear colour distortions - such as colour channel cross coupling, and colour dependent gamma variations - which are at the heart of the look and emotion associated with film image.

Note: The Kodak Vision 2383, Kodak Premier 2393, and Fuji Super F-CP 3510 film profiles provide as standard within LightSpace are all based on real film colourimetry data, measured from the specific film stocks using a highly accurate spectrophotometer.

Kodak AIM Log Image
LightSpace LUT - 1D Graph
LightSpace LUT - 3D Cube
LightSpace LUT Applied

As can be seen above, the LightSpace Film Emulation LUT (as available as a download via the via the Look LUTs page) maintains all the film's non-linear colourimetry, as shown by the 3D Cube view, as well as maintaining a D65 white point/grey scale throughout. The LUT, when applied to the Log image, generates a very accurate film emulation, but with a D65 white point rather than film's D50 (warm) white.

Alternate LUT-1 - 1D Graph
Alternate LUT-1 - 3D Cube
Alternate LUT-1 Applied

The first alternate Film Emulation LUT has a cooler (blue) mid tone grey scale, with harsher peak white clipping, and lacks volumetric colour accuracy. It also has excessive gamut desaturation, as can be seen by the compressed 3D cube.

Alternate LUT-2 - 1D Graph
Alternate LUT-2 - 3D Cube
Alternate LUT-2 Applied

The second alternate Film Emulation LUT has a closer to neutral D65 grey scale, but this time pushes yellow very hard, resulting is a very unpleasant and inaccurate over all colour balance.

Alternate LUT-3 - 1D Graph
Alternate LUT-3 - 3D Cube
Alternate LUT-3 Applied

The third alternate Film Emulation LUT has a neutral D65 grey scale, but lifts the black point into grey, and reduces the peak white point. This may be an attempt to generate a Video Scale LUT, but most creative software expect the LUT to be full-range. The volumetric colour also lacks any true film non-linear management, and little attempt to manage the underlying Log data of the source image(although this was advertised as a LUT for Log footage).

Alternate LUT-4 - 1D Graph
Alternate LUT-4 - 3D Cube
Alternate LUT-4 Applied

The fourth alternate Film Emulation LUT has a close to neutral D65 grey scale, but makes little attempt to manage the underlying Log data of the source image(although this LUT was also advertised as being for Log footage). It has absolutely no non-linear volumetric data, and simply performs a desaturation on the image.

Alternate LUT-5 - 1D Graph
Alternate LUT-5 - 3D Cube
Alternate LUT-5 Applied

And the fifth LUT is an example of just how bad some LUTs can be, even when not attempting to be true film emulations. This LUT is simply bad in just about every way...

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.

1D LUT Conversion

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'.

1D LUT 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...

Alternative to 1D LUT Conversion & Invert

Within LightSpace there are many different ways to reach any end result.

An alternative to using the 'Filters' to generate a 1D only LUT from a 3D LUT is to simply export the LUT in any of the available 1D LUT formats. This exported 1D LUT will strip out the colourimetry (Gamut) data, leaving just the contrast (Gamma) information.

With the 1D LUT exported, you can then use the 'Subtract' function to subtract the exported 1D LUT from the original 3D LUT, rather than using the 'Invert & Addition' workflow outlined above. The resulting LUT will have no contrast component at all, but will contain all the 'film colourimetry'.

The resulting LUT is as follows, with no contrast alteration, but all the original colourimetry.

3D LUT No Contrast
3D LUT Colourimetry

The result of such as LUT would be to alter just the colourimetry of the image.

Marcie TV Legal Image
Marcie TV Legal LUT Applied

However, we actually want a LUT that has 'some' of the film's contrast 'feel', and so we will use the 'Smooth' filter to reduce the accuracy of the inverted 1D LUT, so that when the original LUT is 'Added' to the inverted 1D LUT some of the 'contrast' look and feel is retained.

Smooth Filter
Result of Smooth Filter

When the original 3D Film Look LUT is added to this 'Smoothed' 1D LUT the resulting 3D LUT will retail some of the Film 'contrast' look & feel, as well as all the colourimetry.

3D LUT Partial Contrast
3D LUT Colourimetry

The result of such as LUT would be to have some alteration of contrast, plus alter the colourimetry of the image.

Marcie TV Legal Image
Marcie TV Legal LUT Applied

And it should be obvious that the same approach can be used to alter the contrast change of the original Film Look Log LUT, using different 'Smooth' filter settings to attain the desired end result.

Alternative De-Log

Within LightSpace there are many different ways to reach any end result.

To de-Log any LUT you can also use the 'Edit/LUT Manipulation/Prepend/Log->Vid' function, which will perform a standard 'Cineon' de-Log function. If necessary, after the de-Log function has been applied the 'Edit/LUT Manipulation/Gain' and 'Edit/LUT Manipulation/Lift' functions can be used to re-scale the LUT black and white points as needed.

ARRI Log LUT based on ACES data

The 'ARRI Log Look LUT based on ACES data' was made using ACES V1 CTL data, as outlined on the Working with ACES & LightSpace CMS website page, and is not a Film Emulation LUT as it takes the Arri Log C data and maps into Rec709 using ACES data.

With the necessary ACES CTL tools installed on the LightSpace CMS PC, the following is the procedure used to generate the Look LUT.

First, use 'File/New' to make a blank LUT that has no conversion effect at all. This will be the base on top of which the ACES data will be applied to generate the Look LUT.

Then use 'Edit/ACES CTL/ACES Import' to navigate to the ACES folder and select the CTL file to be used in generating the Look LUT.


The 'ACES Import' selection will allow you to navigate to the ACES CTL files, which need to all be contained within one folder on the PC, as you will need to select the required CTL files together, in the correct order.

Hold down the keyboard 'Control' button and select each CTL file in turn with a mouse 'Left Click'. When selecting multiple CTL files they must be selected in the right order for processing within LightSpace. If the order is wrong, the generated LUT will be wrong.
(Note: When selecting multiple CTL files they must be selected in the right order for processing within LightSpace. If the order is wrong, the generated LUT will be wrong. Check the order in the lower 'File Name' box. Due to Windows operating issues you may need to alter the 'Show By' column selection as this can confuse the selection order.)

For the process being described here first click the IDT, then the RRT, and finally the ODT. When all three files have been selected, click 'Open' to start the LUT Generation process.

ACES Import
Result of ACES Import

The ARRI ACES Look LUT is basically now complete, and can be exported in the required LUT format.

But, as we are generating a Look LUT, not a technical LUT we actually do not want the 'black clipping' the ACES data has caused. While this is technically correct, for a Look LUT it would be better to be able to 'see' into the blacks, so we will use the 'LUT Manipulation/Filters/Relax' followed by 'LUT Manipulation/Filters/Smooth', and finally 'LUT Manipulation/Filters/Axis Blend'.

Applying a Relax Filter
Applying a Smooth Filter
Applying an Axis Blend Filter

The final resulting LUT will have the blacks smoothed-out, with no black clipping. The LUT colourimetry is also very simple, with no applied film emulation, but including the unwanted RRT colour distortion (see the ACES Overview and LightSpace ACES User Manual for more information).

ACES 3D LUT Colourimetry

The result of the LUT is to apply the colour transforms as extracted from the ACES CTL files to any image the LUT is used with. Here, we will use an Alexa image from one of Geoff Boyle's CML Camera Tests.

ARRI Log Original Image
ARRI Image LUT Applied

Again, it should be obvious that the LUT can be adjusted as required to generate different Look LUTs using the different LUT manipulation Filters on top of the applied ACES CTL data. This particular Look LUT may benefit from a small amount of 'Saturation Reduction' for example.

Camera Technical & Look LUTs

Arri Camera

The Camera Settings options within Convert Colour Space enables the generation, previewing, and analysis of Look and Technical Conversion LUTs for a range of digital cinematography cameras, specifically those that shoot and capture Log and Wide Colour Gamut.

Supported camera manufacturers presently includes a generic Rec709 camera, Sony, Arri, Canon, Red, Panasonic, Blackmagic, and DJI, with other added as and when different manufacturers provide access to their camera's technical data.

Using the inbuilt controls within the Camera option, both Technical and Looks LUTs can be generated.

For additional information see the Camera LUT Options page of the website.


Please see the General Downloads page of the website to access downloads.