Gen5 Update

The PowerGrades and LUTs have now been updated to work with the Gen5 colour science. It is recommended you update your camera to the 7.3 firmware or newer and update Resolve to version 17.2 or newer. This guide has also been updated to reflect the new Gen5 workflow.

Whats new in the Gen5 update

The PowerGrade and post-production LUTs now come in two new versions. PxK2Alexa_Gen5_LogC and PxK2Alexa_Gen5_BMD_Film. Both versions only work with Gen5 footage, so make sure the Gen5 Colour Science is selected in the raw tab. ISO specific versions are now no longer required as Gen5 ensures consistency regardless of the ISO. Input_Scaled versions are also no longer required as Gen5 keeps all the image data within range.

1. The PxK2Alexa_Gen5_LogC PowerGrade/LUT outputs a LogC image and is fully compatible with any LUT or PowerGrade that expects ARRI LogC as the input. Use this if you need to match Alexa footage on the same timeline or if you need to share looks between the two cameras without modifying looks.

2. The PxK2Alexa_Gen5_BMD_Film PowerGrade/LUT outputs Alexa colours but in Gen5 BMD Film log. The output won’t match LogC Alexa footage, but it gives you the benefit of the extra highlight range of Gen5. Which means you don’t need to manually grade highlights back down into range. Use this if you want the Alexa colours but don’t need to intercut with Alexa footage.

I’ve also added two new Rec709 output LUTs. These new LUTs have been modified for more filmic saturation and were born from my research into film emulation. They allow for deeper, richer colours whilst avoiding over-saturation. They are tailored specifically for the two different versions of the transforms as mentioned above. For the PxK2Alexa_Gen5_LogC PowerGrade/LUT, these new LUTs are ARRI_LogC2Video_709_V2.cube and ARRI_LogC2Video_709_WDR_V2.cube. For the PxK2Alexa_Gen5_BMD_Film PowerGrade/LUT they are BMD_Gen5_Film2Video_709_V2.cube and BMD_Gen5_Film2Video_709_WDR_V2.cube.

I’ve also added two new Gen5 in-camera LUTs. These are PxK2Alexa_Rec709_Gen5_OnSet.cube and PxK2Alexa_Rec709_WDR_Gen5_OnSet.cube.

And if you have purchased the LUT version of PxK2Alexa I’ve also added two Gen5 all-in-one post-production LUTs. These are PxK2Alexa_Rec709_Gen5.cube and PxK2Alexa_Rec709_WDR_Gen5.cube.

UNDERSTANDING THE TRANSFORM

The standard PxK2Alexa transform is divided into two components, the camera match transform and the output transform.

The first component or transform matches the cameras in linear space and outputs the image in log. It takes Blackmagic Design Film Gen 5 footage from the P6K/P4K as the input, linearises the image, matches it to the Alexa, then outputs this match as ARRI LogC/Alexa Wide Gamut.

The second component is an output transform LUT that takes the ARRI LogC/Alexa Wide Gamut image and converts it to Rec709. This takes the flat desaturated log image, applies a LogC to Rec709 2.4 gamma curve, an Alexa Wide Gamut to Rec709 matrix and outputs an image with restored contrast and saturation that will look correct on your display.

WHY TWO TRANSFORMS?

The main reason is so that footage converted with PxK2Alexa can be integrated into existing colour grading workflows designed for the Alexa, or so that it can integrate alongside footage from the Alexa allowing the same look to be applied to both sets of footage with little or no modifications.

The key component of PxK2Alexa is the camera match transform. This is actually where the “Alexa look” lives. The output transform, while important, isn’t actually a large part of what gives the Alexa its distinctive look. In most Alexa productions, the default ARRI Rec709 output transform LUT used in camera, is discarded when it comes to grading. And all grading is carried out on the ARRI LogC/Alexa Wide Gamut image. Therefore using just the first component of PxK2Alexa places the BMPCC footage at an equal start point to real Alexa footage. From this point the BMPCC footage can be treated as if it was real Alexa footage. Any grade, PowerGrade, look or LUT designed for the Alexa can now be used on the footage with little or no modification.

WHEN YOU MIGHT WANT TO USE A SINGLE COMBINED TRANSFORM

In some situations or workflows it might be necessary to use a single combined transform. A combined transform is useful for previewing the look on-set via a LUT as it would be impractical and unnecessary to use two transforms at this stage. It can also be useful to use a combined LUT at the edit stage so you can work with a more finished looking image. Combined in-camera/on-set LUTs can be found in the PxK2Alexa Rec709 In-Camera and On-Set LUTs folder. If you purchased the LUT version of PxK2Alexa, high quality combined LUTs for post production can be found in the PxK2Alexa Rec709 Post-Production folder.

IMPROVING THE STANDARD ARRI REC709 OUTPUT TRANSFORM

While the standard ARRI Rec709 LUT is probably the best of all camera manufacturer LUTs, it can still be improved on. As part of 2Alexa I have made some modifications to the standard ARRI LUT. These new LUTs have been modified for a more finished look with more filmic saturation. They were born from my research into film emulation. They allow for deeper, richer colours whilst avoiding over-saturation. The new LUT is called ARRI_LogC2Video_709_V2.cube. And a lower contrast wide dynamic range version is called ARRI_LogC2Video_709_WDR_V2.cube

Camera SIDE SETUP

On the camera side the setup is very straightforward. And if you’re shooting in BRAW, in most situations you don’t really need to worry about these settings as they can be adjusted in post. However in some situations the ISO setting will be factor as that can affect how you expose the image, more on that below. If however you shoot in Prores, the correct settings are of more importance.

The recommended camera settings for Prores/BRAW is as follows:

Gamma: Blackmagic Design Film Gen 5
Gamut: Blackmagic Design
ISO, Temp/Tint: Use whatever settings you need to achieve the look you are after. The new Gen5 versions of the transforms offer increased flexibility, allowing you to shoot at any ISO, Temp/Tint combination while maintaining accuracy.
LUTs: I use PxK2Alexa_Rec709_Gen5_OnSet.cube for most situations. But if I’m shooting something with a lot of dynamic range and need a better idea of what is happening in the highlights/shadows I use PxK2Alexa_Rec709_WDR_Gen5_OnSet.cube.

Gamma and Gamut

The Blackmagic Design Film Gen 5 gamma and Blackmagic Design colour space preserve the bulk of the sensor data which makes them ideal candidates as the input for the Alexa conversion. If your footage is shot in BRAW make sure you decode to these settings. If you shoot in Prores make sure your camera is setup to record to these settings.

The PowerGrade version also accepts footage decoded as linear, see the usage instructions below for more details.

ISO

You can shoot at any ISO but I find that ISO800 is the closest match to the Alexa. Not only because it matches the Alexa’s native base ISO of 800, but also because it narrows the gap between the cameras when it comes to highlight handling. But I recommend you shoot at whatever ISO is appropriate for the shot, it doesn’t affect the accuracy of the transform.

Rating the P6K/P4k at ISO800 does increase noise slightly, but in my testing it’s only slightly more noise than an Alexa shooting 2.8K ARRIRAW. I still recommend you shoot your own tests and determine what level of noise you are comfortable with.

Temperature and Tint

Temperature and tint is now totally flexible. The new Gen5 versions of the transform no longer internally adjust the temp/tint, they are now faithful to the temp/tint set in-camera or in the raw tab.

If you’re shooting in Prores I recommend getting as close as possible on set, then fine tuning with the offset wheel in Resolve. In general I dial in the big moves in the raw tab or on set, apply the settings to all clips, then fine tune shot to shot differences with the offset wheel.

Filtration

One of the biggest factors that can affect the quality of your footage and the accuracy of the transform. Variable NDs, IRNDs and IR cut filters can introduce colour casts. However, this is fairly easy to correct for. The easiest method is to shoot an outdoor scene with and without filtration, then in Resolve use the temp and tint controls to match the filtered shot to the unfiltered shot. These settings will be your new neutral temp and tint settings.

For example, the Hoya UV & IR Cut filter adds a slight green tint, but it can easily be offset by adding +5 Tint. I also noticed that it adds a minor green/blue vignette which is more prominent on wide angle lenses. This can be corrected with a circular Power Window and the offset wheel.

Correct Exposure AND ETTR

Part of what makes Alexa footage look so good is correct exposure. This ensures deep rich colours, rich skin tones and correct contrast via maximised use of the sensor’s dynamic range. This means methods such as ETTR should be avoided.

ETTR is ok for cameras recording to 8bit codecs, but ETTR is unnecessary for cameras recording 10 or 12bits to high quality codecs like BRAW or even Prores 422HQ.

ETTR creates issues with differing noise levels and exposure not matching between shots in the same scene. This is due to the exposure being dictated by the brightest object in the scene. And if the brightest object in the scene disappears or changes brightness, ETTR dictates that you change your exposure. Which means shots from the same scene won’t match in exposure or noise level. What might be even worse, is that it is possible to expose so far to the right that it is difficult to return correct contrast back to the shot, as the majority of the shot lives in the upper linear portion of the log curve.

A much better method than letting highlights dictate exposure, is to expose for the middle of the shot, or middle gray. AKA 18% gray. The theory here is that if you expose for middle gray on a sensor that has equal stops above and below middle gray, you’ll be able to accurately capture the entire dynamic range of the scene with correct contrast, with minimal or no clipped highlights and all at an acceptable noise level. And the exposure will be consistent between shots and scenes. With cameras like the P4K/P6K, it is possible to do this for most scenes.

False Colour

The easiest method to expose for middle gray is to use false colour. With false colour enabled on the P4K/P6K shooting at ISO800, anything that is highlighted green is being exposed exactly at the middle of the sensor’s dynamic range. Along with green the BMPCC also uses pink (1 stop brighter than middle gray) to help you expose skin. For most shots featuring people, all I do is place green towards the shadow side of the skin, and place pink on the lit side of the skin. Any skin tones between those colours will be right in the sweet spot. For darker complexions it’s possible place green further towards the lit side of skin to avoid overexposure.

For scenes that don’t feature people, it’s a bit more flexible. Generally I place green on or near the focus of the scene. But paying close attention to the brightness of that focus. Placing green on a white polar bear in snow will result in an underexposed image. Here you need to use judgement and experience to gauge correct exposure. And for this example I would probably look to place pink on the shadow side of the polar bear.

I also like to setup zebras to appear at 100%. Mainly as a final check to make sure that nothing of importance in the scene is being clipped.

How do you know when you have correct exposure?

If you can take your footage into Resolve and apply P4K/P6K2Alexa and without any adjustments the skin brightness looks correct, you can simultaneously see detail in the shadows and highlights, and you have no urge to adjust exposure, then your exposure is spot on.

For some projects shot by talented DPs, I can grade the entire project without adjusting exposure. Thats the level of accuracy possible with false colour.

If you need to correct ETTR or overexposed shots see the Solving Issues section below.

Installation and Usage

In-Camera LUT installation

The in-camera LUTs can be found in the PxK2Alexa Rec709 In-Camera and On-Set LUTs folder. For instructions on importing and applying LUTs on the P6K/P4K, check pages 85-86 of the BMPCC Operational Manual which can be found here: https://www.blackmagicdesign.com/support/family/professional-cameras

LUT VERSION Resolve Installation

Extract the zip file, open Resolve and bring up Project Settings. Navigate to the Color Management tab on the left and find the Lookup Tables section. Click the Open LUT folder and copy over the P6K2Alexa/P4K2Alexa folder. If you also want the all-in-one Rec709 versions you can also copy the PxK2Alexa Rec709 Post-Production folder as well. Navigate back to Resolve and click the Update Lists button. The LUTs will now be accessible inside Resolve.

Resolve Color Management Setup

In the Color Management tab make sure the Color Science is set to the default of Davinci YRGB and the Timeline Color Space is set to Rec.709 Gamma 2.4. The non ACES PowerGrades are currently not compatible with the Davinci YRGB Color Managed workflow. I’ll look at creating compatible versions in the future.

Using the LUT VERSION in Resolve

This is the basic node structure I use with the LUT. Make sure your Color Management settings are set according to the Resolve Color Management section above. And make sure Color Science is set to Gen5 in the raw tab.

Node 01 is noise reduction. I generally use Spatial NR with Mode set to Faster, Radius set to Small. Then under Spatial Threshold I unlink Luma and Chroma and leave Luma at 0.0 and set Chroma to around 8.0.

Node 02 is used for fine tuning the image balance. Generally to correct for shot to shot differences as the overall balance is best handled in the raw tab. If the footage is Prores, the bulk of the balancing will take place in this node. Since this node sits in BMDFilm log space I would use the offset wheel to make exposure or colour adjustments. Just pay close attention to exposure as it can cause the LUT to clip.

Node 03 is the PxK2Alexa transform LUT. Select either PxK2Alexa_Gen5_LogC.cube or PxK2Alexa_Gen5_BMD_Film.cube.

The gap between Node 03 and 04 this is where creative grading takes place.

Node 04 is the output LUT. What LUT you select here depends on what PxK2Alexa transform LUT you are using.

• If you are using PxK2Alexa_Gen5_LogC.cube in Node 03, select either ARRI_LogC2Video_709_V2.cube or ARRI_LogC2Video_709_WDR_V2.cube or any other LUT included with PxK2Alexa that begins with “ARRI_LogC2Video_709”. Or even any other LUT you might have that is designed for ARRI LogC.

• If you are using PxK2Alexa_Gen5_BMD_Film.cube in Node 03, select either BMD_Gen5_Film2Video_709_V2.cube or BMD_Gen5_Film2Video_709_WDR_V2.cube. If you want to use other LUTs or PowerGrades designed for ARRI LogC you will need to use a Color Space Transform node prior to this node to convert just the gamma, from BMD Film Gen5 to ARRI LogC. Then apply the LUT in this node as normal.

PowerGrade Installation

To install the PowerGrades in Resolve, in the Gallery tab find the PowerGrade 1 stills album. Adding the PowerGrades to this album will allow you to access the PowerGrades from any project and it also means you only have to add them once. Once selected second mouse button click in the gallery window background and select Import. If it doesn’t let you select a file, you might need to click the options button at the bottom of the import window and then select .dpx or .drx from the list, then try again.

Once installed the PowerGrades can be applied to the selected shot by middle mouse button clicking on the still in the gallery. Or with a second mouse button click and then selecting Apply Grade.

Along with the PowerGrades you’ll need to install the ARRI LogC to Rec709 conversion LUTs. Follow the LUT installation instructions above and copy the PxK2Alexa Rec709 LUTs folder to Resolve’s LUT folder. If you do this incorrectly, your footage will remain as flat log gamma after applying the PowerGrade. You will also get a missing LUT error message.

the PxK2Alexa PowerGrade

Make sure your Color Management settings are set according to the Resolve Color Management section above. And make sure Color Science is set to Gen5 in the raw tab when using the Gen5 PowerGrades.

Node 01 corrects the individual RGB channels via the RGB curves.

Node 02 is a CST node that transforms Blackmagic Design Film Gen5 to linear.

Node 03 is for accurate exposure adjustments using the master gain wheel (the slider under the main gain colour wheel), which is especially useful when working with Prores footage. Doubling the gain from 1.00 to 2.00, 2.00 to 4.00 etc increases the exposure by precisely 1 stop each time you double the value. And halving from 1.00 to 0.50, 0.50 to 0.25 etc decreases the exposure by 1 stop each time you halve the value. This exposure adjustment method can also be useful when working with footage that has been shot ETTR, more on this at the bottom of the page. You can also colour balance by using the gain wheel, which results in more accurate and cleaner results than using the offset wheel and sometimes even better results than the temp/tint controls in the raw tab.

Node 04 is the 3x3 matrix and the core of the transform. This matrix lives in the RGB mixer and it aligns the P4K/P6K colours to match the Alexa.

Node 05 is a CST that transforms the image from linear into either ARRI LogC or Blackmagic Design Film Gen5 depending on which version of the PowerGrade you are using. If you have any colours that are clipping or causing issues, try enabling Gamut Mapping in the CST of this node.

The Gap between Node 05 and 06 is where creative grading takes place.

Node 06 is the highlight roll-off curve. It’s the only creative part of this PowerGrade, hence why it is disabled by default.

Node 07 handles the conversion from either ARRI LogC or BMD Film Gen5 to Rec709, depending on which version of the PowerGrade you are using.

• If you’re using the PxK2Alexa_Gen5_LogC version of the PowerGrade the default LUT here is ARRI_LogC2Video_709_V2.cube. But you can select any LUT from the PxK2Alexa Rec709 LUTs folder that begins with “ARRI_LogC2Video” or any other LUT designed for ARRI LogC.

• If you’re using the PxK2Alexa_Gen5_BMD_Film version of the PowerGrade the default LUT is BMD_Gen5_Film2Video_709_V2.cube. But you can also select BMD_Gen5_Film2Video_709_WDRV2.cube. If you want to use other LUTs or PowerGrades designed for ARRI LogC you will need to use a Color Space Transform node prior to this node to convert just the gamma, from BMD Film Gen5 to ARRI LogC.

I like to treat the footage as if it was shot on a real Alexa and it tends to respond in an almost identical way. The PowerGrade (or the LUT version) allow me to use the exact same grades and workflows I’ve developed for the Alexa, on P4K/P6K footage. And usually with no modifications.

Following my standard Alexa workflow, for most grades I remove Nodes 06 and 07 and replace them with a Print Film Emulation (PFE). Either a real PFE LUT or one of my PFE PowerGrade rebuilds. I used to select all the nodes from 01-05, and group them in a Compound Node to clean up the node graph. But now I’ve started not compounding the nodes as I like to do most of my exposure and temp/tint corrections in the Node 03. So keeping the internals of the PowerGrade visible is necessary.

With or without the PFE, all grading takes places after Node 05 but before the output LUT, PFE LUT or PFE PowerGrade.

Similar to the LUT version of the PowerGrade I always put a noise reduction node before Node 01 and I use the same settings as listed in the LUT section above.

PxK2ALEXA RCM POWERGRADES

The PxK2Alexa RCM PowerGrades allow you to match the P6K/P4K to the Alexa when using the Resolve Color Managed workflow. It should produce better results when using RCM PowerGrades such as the RCM Print Film Emulation PowerGrades.

Node 01 tames the brightest highlights to match the softer look of the Alexa. If you’re delivering in HDR, experiment with disabling this node.

Node 02 corrects the individual RGB channels via the RGB curves.

Node 03 is the 3x3 matrix and the core of the transform. This matrix lives in the RGB mixer and it aligns the URSA G2 colours to match the Alexa.

A node after Node 03 is where I balance the image and make exposure adjustments. This is best done in the HDR Color Wheels panel, using the Global Colour Wheel for balancing out colour casts and the Exp control to adjust exposure. You can also append other RCM PowerGrades such as the RCM PFE PowerGrades after this balance/exp node.

To use the RCM PowerGrades, set the Color science to Davinci YRGB Color Managed, Colour processing mode to HDR Davinci Wide Gamut Intermediate. And then set the Output color space to match your deliverable’s color space.

PxK2Alexa ACES PowerGrade

The node structure is also similar for the ACES version of the PowerGrade. The main difference is Node 07, which approximates the WDR look inside ACES.

To use the ACES version make sure you setup Resolve in ACEScct mode, then apply the PowerGrade as normal. At this stage the PowerGrade only works with BRAW footage as Resolve doesn’t have an IDT for Prores P4K/P6K footage.

Other Software

The are three methods to use the PxK2Alexa LUT transforms in other NLEs. For all three methods make sure your Color Science is set to Gen5 in the raw tab.

1. The easiest method is to use the all-in-one LUTs included with the LUT version of PxK2Alexa. Apply one of the Gen5 LUTS from the PxK2Alexa Rec709 Post-Production folder, then grade underneath this LUT. The way I would set this up in Premiere is to create an Adjustment Layer that sits over the entire timeline. Add a Lumetri effect to the Adjustment Layer and select one of the all-in-one LUTs. Add another Lumetri effect to any clip that needs grading/correction. You can also make adjustments in the raw tab. Corrections to each clip are now happening under the main Adjustment Layer LUT.

2. The second method is slightly more involved but it’s more accurate and closer to working with real Alexa footage. It It also gives you more flexibility as you can choose to use any output LUT made for ARRI LogC. The way to set this up in Premiere is to apply a Lumetri effect to a clip, then in the Input LUT field select the PxK2Alexa_Gen5_LogC.cube LUT from the PxK2Alexa/PxK2Alexa Log folder. Then copy this Lumetri effect to every clip in your timeline. Create an Adjustment Layer that sits over the entire timeline, add a Lumetri effect to it and select any LUT from the PxK2Alexa/Alexa Rec709 folder that begins with “ARRI_LogC2Video_709.” You can also select any LUT made for ARRI LogC. Any corrections made to the Lumetri effect at the clip level are happening under the main Adjustment Layer LUT.

3. The third method is the same as above but instead of selecting the PxK2Alexa_Gen5_LogC.cube LUT, select PxK2Alexa_Gen5_BMD_Film.cube. In the Adjustment Layer Lumetri effect you have the choice of selecting either BMD_Gen5_Film2Video_709_V2.cube or BMD_Gen5_Film2Video_709_WDR_V2.cube. The benefit of this workflow is full access to the extra highlight range of the Gen5 film curve. This is especially useful if you shoot ISO640 or higher and use the highlight recovery option, as all the highlight information is visible. Which is not the case when using the LogC curve.

Solving ISSUES

Correcting ETTR and Overexposed shots

Questions, Comments, Support

For questions, comments or if you need LUT/PowerGrade support feel free to contact me at support@juanmelara.com.au