Logarist

Video Color Correction



Contents

Introduction

Logarist brings color science to the art of color correction, enabling fast and accurate adjustment right inside your video editing application, without the need to shoot raw. Logarist reduces color correction to its fundamentals, with controls that work much like the controls built into a camera or a raw image processor like Lightroom. Logarist uses look-up tables (LUTs) to transform your camera's video into a color space optimized for exposure compensation, white balance correction, and contrast adjustment, and then renders it for view on a standard display. Logarist makes basic color correction easy and accurate, and enables advanced corrections that are otherwise difficult or impossible. Logarist is free, and you can download it from this web site.

Watch the Logarist introduction and demo/tutorial video on YouTube:
YouTube: Introduction to Logarist

Supported Video Applications

Supported Camera Color Spaces

Download Logarist

Logarist for Adobe Premiere (Win)
Logarist for Adobe Premiere (Mac)
Logarist for DaVinci Resolve (Win)
Logarist for DaVinci Resolve (Mac)
Logarist for Final Cut Pro X
Logarist for Vegas Pro

Version History

Discussion Topics

Logarist at personal-view.com
Logarist at dvxuser.com
Logarist for Vegas Pro at vegascreativesoftware.info

How Logarist Works

Logarist uses look-up tables, or LUTs, to transform between color spaces.  Logarist LUTs are always used in pairs.  The first LUT transforms from your camera's color space into the Logarist color space.  The second LUT transforms into the display color space.  Color correction is performed in the Logarist color space, between the two LUTs.


Display Rendering and Highlight Compression in Logarist

Logarist renders images for standard computer monitors, mobile displays, and TVs using Recommendation ITU-R BT.709 (sometimes called Rec.709).  BT.709 renders images with normal contrast across its dynamic range.  But standard monitors are not very bright, and so BT.709 is unable to reproduce very bright highlights, even if your camera is capable of recording them.  Bright highlights may be clipped in BT.709, with a harsh and unnatural appearance.  Logarist extends the highlight range of BT.709 with several optional highlight compression curves:
HighComp refers to highlight compression using curves applied equally to the Logarist Red, Green, and Blue color channels before transformation to BT.709.  Compressing the highlights this way is fairly typical.  It will reduce their saturation and shift some hues (especially skin tones, which shift towards green), though hue shifts are smaller in Logarist than they are in smaller gamut color spaces.  In some situations those changes in saturation and hue will be undesirable.

LumaComp refers to highlight compression using a curve applied to the Luminance (CIE 1931) channel before transformation to BT.709.  Compressing the highlights this way does not alter saturation or hues.

The number refers to the amount of highlight extension, measured in stops - from 1/3 stop to 1 and 1/3 stops.

These highlight compression curves are provided as an optional convenience to the user.  You may instead wish to use standard BT.709 with no curve, or with a curve that you define yourself in your video editing application.

Video Application Instructions

Premiere Pro

Logarist has been tested in Premiere Pro CC 2015 and CC 2017. Earlier CC versions, CS5.5, and CS6 should also work.  On Macs, macOS 10.9 or later is required.

Download the Logarist package (above) and install it. Restart Premiere Pro to load the new plugin.

  1. Open a project and switch to the Effects workspace.
  2. Click on a video clip in the timeline to select it.
  3. From the Effects panel, Video Effects, Color Correction, drag the Logarist effect onto the video clip in the timeline.
  4. In the Effect Controls panel, click the Logarist effect's setup button:
    1. Under Input LUT, click Open..., browse to a camera-to-Logarist LUT file, and then click Open.
  5. In the Effect Controls panel, click the Logarist effect's setup button:
    1. Under Output LUT, click Open..., browse to a Logarist-to-BT.709 LUT file, and then click Open. I usually choose BT.709 LumaComp 0.66.
  6. Perform color correction:
    1. Adjust the Exposure, Red, Green, Blue, and Contrast parameters by clicking and dragging the numbers up or down.  You can also use the sliders.
Premiere Pro Tips:

Premiere Elements

Windows users: Logarist has been tested in Premiere Elements 15. 64-bit builds of earlier version of Premiere Elements should also work. If you have a 32-bit build of Premiere Elements installed, you can download a 64-bit build of the same version and install it using your serial number.

Mac users: Logarist requires Premiere Elements 11 or later and macOS 10.9 or later.

Download the Logarist package (above) and install it. Restart Premiere Elements to load the new plugin.

  1. Open a project and switch to the Expert view.
  2. Click on a video clip in the timeline to select it.
  3. Click Effects (the second "fx" button, without a pencil)
  4. In the Effects panel, under Video, click the pull-down and select Color Correction.
  5. Drag Logarist from the Effects panel onto your video clip in the timeline.
  6. In the Applied Effects panel, click the Logarist effect's setup button (gear icon).
    1. Under Input LUT, click Open..., browse to a camera-to-Logarist LUT file, and then click Open.
  7. In the Applied Effects panel, click the Logarist effect's setup button (gear icon).
    1. Under Output LUT, click Open..., browse to a Logarist-to-BT.709 LUT file, and then click Open. I usually choose BT.709 LumaComp 0.66.
  8. Now you can perform color correction:
    1. Adjust the Exposure, Red, Green, Blue, and Contrast parameters.
    2. For coarse adjustments, drag the sliders right or left.
    3. For fine adjustments, drag the numbers up or down.
Premiere Elements Tips:

DaVinci Resolve

Download the Logarist package (above) and install it according to the instructions in the readme file.

  1. Set up your project:
    1. In Main Project Settings: set Color science to DaVinci YRGB.
    2. In Color: uncheck "Use Legacy Log grading ranges and curve".
    3. In Color: uncheck "Use S-curve for Contrast".
    4. In Color Management: set "3D Lookup Table Interpolation" to Tetrahedral.
  2. Configure clip properties:
    1. In the Media or Edit workspace, select all of the clips that you want to use with Logarist, right click, click Clip Attributes..., and set Data Levels to Video.  The Logarist LUTs all expect the video files to be read using video levels, regardless of which levels the files actually use.
  3. Color correct:
    1. Set a camera-to-Logarist LUT:  right click on the clip, click 3D LUT, and then set the camera-to-Logarist LUT that corresponds to the color space of the clip.
    2. Set an output LUT:  in the Color workspace, right click on a corrector node, and set the 3D LUT to one of the Logarist-to-BT.709 LUTs.
    3. Working in that corrector node, you can do basic color correction with Color Wheels set to Log mode:
      1. Exposure compensation:  drag the Offset master wheel left or right.
      2. White balance correction: adjust the Offset color balance control.
      3. Contrast adjustment:  set the pivot to 0.5 and then adjust the contrast.
Color Correction Tips:

Vegas Pro

Download the Logarist package (above) and install it according to the instructions in the readme file.  Logarist LUTs are loaded using the VisionColor LUT Plugin.  The plugin is free, and requires Vegas Pro 13 or later.  You need to go through VisionColor's checkout to download the plugin.  Download and install the plugin, and then restart Vegas Pro. 
  1. In Project Properties:
    1. Set the Pixel format to 32-bit floating point (full range).
    2. Set the Compositing gamma to Video.
    3. Set the View transform to Off.
  2. Add Event FX to your video event in this order:
    1. VisionColor LUT Plugin
    2. Brightness and Contrast
    3. Channel Blend
    4. VisionColor LUT Plugin
  3. On the first VisionColor LUT Plugin, load a camera-to-Logarist LUT file.
  4. On the second VisionColor LUT Plugin, load a Logarist-to-BT.709 LUT file.
  5. Perform color correction:
    1. Exposure compensation:  in the Brightness and Contrast filter, drag the brightness slider.  Hold down Ctrl to make fine adjustments.
    2. White balance correction: in the Channel Blend filter, adjust the Red, Green, and Blue offsets in the last column.  Hold down Ctrl, click between the up and down arrows, and drag up or down to make fine adjustments.
    3. Contrast adjustment:  in the Brightness and Contrast filter, drag the contrast slider.  Hold down Ctrl to make fine adjustments. 

Final Cut Pro X

Download the Logarist package (above) and unzip it to a location of your choice.  Logarist LUTs are loaded using the mLut Plugin by motionVFX.  Logarist will not work correctly with other LUT plugins. The mLut Plugin is free. To download the plugin from the mLut Plugin page, click GET NOW to add it to your cart, click the cart button, sign up for an account with motionVFX, complete the checkout process, and install the plugin using mInstaller and your motionVFX account. Restart Final Cut Pro X after installing the mLut Plugin.

  1. For clips recorded in Canon Log, S-Log2/3, or VariCam V-Log, make sure Final Cut Pro's built-in log processing is turned off.
  2. Use the Effects Browser to add effects to your video clip in this order:
    1. mLut by motionVFX
    2. Color Correction
    3. mLut by motionVFX
  3. Click the clip to select it, and open the Inspector.
  4. In the first mLut effect:
    1. Uncheck HUE/SATURATION.
    2. Click Load Custom LUT, and browse to a camera-to-Logarist LUT file.
    3. Note the end of the LUT filename and whether it says [Highlights 1.1].  Click Load.
    4. If the filename ended in [Highlights 1.1], click on the Highlights value, type 1.1, and hit Return.
  5. In the second mLut effect:
    1. Uncheck HUE/SATURATION.
    2. Click Load Custom LUT, browse to a Logarist-to-BT.709 LUT file, and click Load.
  6. Perform color correction:
    1. In the Color Correction effect, click to open the Color Board.
      1. Click Exposure, and then adjust the Global Exposure. You can drag the global control on the left, or click the percentage and use the up and down arrow keys to make fine adjustments.
      2. Click Color, and then adjust the Global Color.  The hue angle can be quickly changed by dragging the angle value up or down.  The percentage can be adjusted by clicking on the value and then using the up and down arrow keys.
    2. Use the Contrast slider in the second mLut effect to adjust the contrast.

To make finer color adjustments:

  1. Follow the above instructions, but use two Color Correction effects between the mLut effects instead of one. 
  2. In the first Color Correction effect, set Exposure Shadows to -100.
  3. In the second Color Correction effect, set Exposure Shadows to 50.
  4. Now color correction can be performed on the first Color Correction effect according to the above instructions.  Exposure and color corrections will be twice as fine, meaning each percentage would need to be doubled to achieve the same effect.

Camera Instructions

Standard HD Cameras

If your camera doesn't record to one of the color spaces explicitly supported by Logarist, it probably records to something that is similar to BT.709.  For these cameras you can use a BT.709 to Logarist input transform.  This will allow you to perform basic color correction, though it won't be as accurate as if you were using a supported camera color space.  The Logarist BT.709 input transform can't undo the non-standard effects of your camera's color processing.  The larger the color corrections you make, the greater the color errors will be, as the differences between your camera's output and BT.709 will be amplified. 

If your camera has a knee setting, disable it if possible, or set the knee parameters as high as they will go.

In Vegas Pro and in DaVinci Resolve for Windows, two different BT.709 input transforms are available:

Which transform you should use depends on your camera and its recording format.  You need to test to find out.  Shoot a test video with the lens cap on.  Bring that video recording into your video application, and apply the BT.709 full_range to Logarist LUT and then the Logarist to BT.709 LUT.  Check your scopes.  If the scopes show the camera's black at 0%, your camera uses full_range encoding.  If the scopes show black at 6%, your camera uses video_levels encoding.

Logarist's BT.709 input transforms support RGB values above 100% (superwhites).  Values below 0% are supported also, consistent with xvYCC.

Canon EOS DSLRs and EOS M Mirrorless Cameras

Logarist provides an input transform for H.264 .MOV and .MP4 videos in the EOS Neutral picture style.  The camera should be set as follows:

If you don't use the above settings, the camera's color space won't match what the Logarist transform is expecting, and colors will be transformed incorrectly.  If using DaVinci Resolve, make sure that each clip's Clip Attributes has Data Levels set to Video.  The Logarist LUTs expect this and will make the necessary compensation.  Add your camera's video file directly to the timeline, without any prior conversion, as conversion might alter the levels.  MJPEG files (e.g. from the 1D C, 1D X Mark II, and the 5D Mark IV) have not been tested: I'm not certain that Logarist will map levels correctly for those videos.

Canon EOS Cxxx Cinema Cameras

Different C-series cameras support different color spaces.  Refer to this table and make sure you select the Logarist input transform that corresponds to the color space generated by your camera:

C100, C100-II, C300
C500 MXF & HD-SDI
C500 3G-SDI & mon.
C300-II, C700
Canon Log (daylight or tungsten)




Canon Log, BT.709 Gamut



Canon Log, DCI-P3 Gamut



Canon Log, DCI-P3+ Gamut



Canon Log, BT.2020 Gamut



Canon Log, Cinema Gamut



Canon Log 2/3, BT.709 Gamut


Canon Log 2/3, DCI-P3 Gamut


Canon Log 2/3, BT.2020 Gamut


Canon Log 2/3, Cinema Gamut



The Logarist Canon Log daylight and Canon Log tungsten transforms correspond to the Canon Log preset on all of these cameras.  The Canon Log preset means a Gamma setting of Canon Log and a Color Matrix setting of Canon Log.  (or on the C300mk2 and later, Canon Log Gamma, BT.709 Color Space, and Cinema EOS Original Color Matrix)  Choose daylight or tungsten according to the illuminant under which the video was shot.  If using DaVinci Resolve with AVCHD .MTS files from the C100 and C100mk2, make sure that the clip attributes data range is set to Video, because Resolve will likely guess wrong if set to Auto.

On the C500, different color spaces are available on different outputs.  The color space of the 3G-SDI terminal and the monitor terminals is affected by the camera's Color Space setting.  If recording from one of the monitor terminals, make sure the camera's LUT setting is set to Off.

Note to C300mk2 users with Final Cut Pro X:  firmware version 1.0.6 (released December 2016) incorrectly sets the full_range_flag in its internally recorded XF-AVC files.  This bug causes levels to be mapped incorrectly in Final Cut Pro X.  For these files, and only these files, use the full_range_flag Logarist LUTs, which compensate for the problem.  For recordings made with older firmware versions, other Cinema EOS cameras, and external recordings, do not use the full_range_flag Logarist LUTs.

On the C300mk2 and later, the Gamma, Color Space, and Color Matrix are independently selectable for every output. The Logarist input transforms with a specified gamut each correspond to the camera's similarly named preset.  These presets all have Color Matrix set to Neutral.

Sony Cameras

On all Sony cameras that support it, I recommend customizing the picture profile with a Gamma setting of Cine1 or Cine2 (HyperGamma 4 or 2) and a Color Mode setting of Still.  Leave all other contrast and color settings set to their defaults (black level, black gamma, saturation, color phase, color depth).  This combination has better quality and color accuracy than S-Log2 or S-Log3, is easier to shoot with, and has the same or better dynamic range (on most Sony cameras).  Compared to S-Log2 and S-Log3, Cine1 and 2 have:

Cine1 and Cine2 are available in most Sony XDCAMs, Sony Alpha cameras since the a7S, the RX100 Mark IV, and the RX10 Mark II.

The only difference between Cine1 and Cine2 is how output levels are utilized.  Cine1 uses an RGB range of 3% to 109%, whereas Cine2 uses an RGB range of 3% to 100%.  Using Cine1, for example, if zebras are set to 100, there's about one stop of additional highlight range between 100% and 109% when zebras start to show.  Using Cine2 with zebras set to 100, it's already clipping when zebras start to show.

Different color mode settings render colors differently. I find Still to be the most accurate, followed by Pro.  I recommend against S-Gamut, which seems to have color accuracy problems, at least on the a7S and PMW-F3.

On Sony XDCAMs with a HyperGamma setting, choose HyperGamma 4 or 2 and set the color matrix to ITU-709.

Note that Sony Cinematone is not the same as Cine1 or 2.  On cameras with Cinematone, use ITU-709 or Standard gamma & color instead, with knee disabled or set as high as it will go.  Then use the BT.709 to Logarist input transform for color correction.

Sony CineAlta Cameras

For CineAlta cameras, Logarist supports S-Log, S-Log2, and S-Log3, each with a standard gamut or with S-Gamut (and S-Gamut3.Cine for S-Log3). Logarist also supports Cine1 and Cine2 with a standard gamut or with S-Gamut3.Cine. I recommend testing different matrix (or gamut) settings to see how color accuracy compares, being particularly wary of S-Gamut.

On the PMW-F3, I recommend setting Dual-Link & Gamma Select to Video, and customizing the picture profile with matrix set to Standard, and gamma set to Cine1 or S-Log. With the RGB444 & S-Log option installed and Dual-Link & Gamma Select set to S-Log, I found the colors to be very inaccurate and not consistent with the S-Gamut specification or with the Sony S-Log ACES IDT.

Panasonic GH2

Logarist provides an input transform for the GH2's Standard film mode.  The film mode must be set as follows:

If using DaVinci Resolve with AVCHD .MTS files, make sure that the clip attributes data range is set to Video, because Resolve will likely guess wrong if set to Auto.

Panasonic GH4

On the GH4, I recommend shooting with the Photo Style set to Cinelike D.  To match what the Logarist input transform is expecting, the camera must be set as follows:
Logarist also has a GH4 V-Log L input transform.  I recommend V-Log L only when recording externally with 10-bit precision.  V-Log L has very poor color precision in 8 bits.  On the Mac, there are two different V-Log L transforms: one for internal recordings, and one for external recordings.  Make sure to choose the correct one.  (No such distinction is necessary in Windows)

Note that the GH4 V-Log L transform is not the same as the VariCam V-Log transform. 

Panasonic GH5

I have evaluated test footage from the Panasonic GH5, and so far it seems that the GH5's Cinelike D color space closely matches Cinelike D on the GH4. Therefore my recommendation for GH5 shooters is the same as for GH4 shooters: shoot in Cinelike D, and then use the Logarist GH4 Cinelike D input transform to process the footage. Refer to the GH4 instructions above for how to set the camera. I found that the GH5's Cinelike D footage processed this way had pleasing color, looking much better than any of the GH5's built-in photo styles. Good results may be obtained shooting with 8-bit or 10-bit precision. Cinelike D has good color precision in 8 bits, so you may opt to record internally in 8-bit 4k/60p.

At this point I cannot recommend shooting in V-Log L. I would need to conduct a more detailed analysis of V-Log L on the GH5 to determine what differences it has with V-Log L from the GH4 and whether Panasonic corrected any of its faults. My GH4 V-Log L transform compensates for those faults, and different compensation may be necessary for the GH5. I do not know if V-Log L holds any potential benefits over Cinelike D on the GH5. (It didn't on the GH4.) Contact me if you'd like to have these questions answered and you can lend me a GH5 for testing.

GoPro

Logarist supports GoPro cameras with Protune when set as follows:

Arri Alexa

Logarist supports the Log C color space of the Arri Alexa (SUP 3.0 or later) and Arri Amira. Logarist comes with input transforms for Log C with the camera's Exposure Index set to 800 or 1600. Contact me for input transforms for other Exposure Index settings.

Raw Images in DaVinci Resolve

Even if you shoot in raw, Logarist enables advanced color correction beyond what Resolve provides natively for raw decoding, like graduated filters and keyframed corrections. In Camera Raw Codec Settings for your video clip, set the Color Space and Gamma to Rec.709.  Then apply the BT.709 video_levels to Logarist 3D LUT to the video clip.  The Logarist BT.709 input transform reads RGB color values up to 130%, so reduce the raw exposure as necessary to keep the BT.709 RGB values below 130% before the Logarist input transform is applied, and then compensate in Logarist. You might be thinking that picture information would be lost by developing the raw image into the narrow-gamut small-dynamic-range BT.709 color space.  That would be true if you were rendering to an 8-bit or 10-bit BT.709 video file.  But in this case, there is no intermediate video file:  Resolve keeps all of the color values in 32-bit floating point, which means no picture information is lost.  Even out-of-gamut colors are preserved, because Logarist decodes them from negative RGB values.

Logarist Compared to ACES

Logarist and ACES are built around some of the same ideas: a common working color space, input transforms, and output transforms.  But Logarist and ACES have different goals.  ACES aims to standardize the interchange and archiving of film and video material for motion picture production.  Logarist aims to make color correction easier in popular video editing applications.  There are other differences:

Logarist Color Space Specification

Logarist is a wide-gamut, high dynamic range, scene-referred tri-stimulus RGB working color space with a uniformly logarithmic opto-electronic transfer function, optimized for 32-bit floating point color correction in video applications.

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