How to Calibrate a Reference Display in CalMAN Studio

Creating A Calibration 3D LUT in CalMAN

November 6, 2017

Part 2 in our calibration series has us doing our first calibration in CalMAN Studio. We generate two different LUTs for our OLED display.


Series
CalMAN Part 2: Reference Display Calibration Series

How to Create (and Verify) a 3D LUT for an RGB OLED in CalMAN

Note: This Insight series is a follow-up to our Display Profiling series. If you haven’t watched that series then you should start here to learn the essentials of CalMAN and LightSpace.

CalMAN Studio: The Color Cube (3D LUT) Workflow

Display calibration isn’t a one-size-fits-all solution. Depending on the exact colorimeter you use and the exact display technology of your reference display, you’re going to modify your display calibration workflow. This series covers multiple display technologies (OLED and LCD). But we have to start somewhere, so we’ll start with a display that’s both one of the most customizable and the one that I use in my shop, the FSI CM250 RGB OLED.

About the RGB OLEDs

FSI’s 24″ OLEDs are top-emission RGB OLEDs. They support uploading 3D (and 1D LUTs), which make them ideal for the 3D LUT workflow you’re about to learn in this Insight. But if you use a LUT box to calibrate your reference display, you follow the same basic workflow as outlined here. But all top-emission RGB OLEDs suffer from a human perception problem called Metamerism Failure.

About Metamerism Failure

As Robbie explains in this Insight on Perceptually Matching two displays, “Put simply, Metamerism Failure is a phenomenon that even when two colors are measured to identical values with a calibrated instrument, they still look different [to the human eye].”

In other words, if you perfectly calibrate any LCD and any RGB OLED and place them side by side then they’ll look different from each other. To deal with this problem, an offset to the white point of RGB OLEDs is applied, which generally overcomes the metamerism failure. This offset is known as the Judd Voss Modified White Point.

About the Judd Voss Modified White Point

The Judd Modified white point doesn’t effect the color gamut of a display… the primary RGB coordinates stay the same. It’s only the white point that changes. As you watch this Insight it’s important to note: The Judd Modified white point only effects RGB OLEDs, almost exclusively found from reference display manufacturers such as Flanders Scientific and Sony. Consumer OLEDs (for example, from LG or Samsung) use a different OLED display technology and the Judd Voss modified white point doesn’t apply.

For a history of Judd Voss, check out this page from Light Illusion.

How to select the proper Luminance Response Target for your display?

Calibration Settings for an RGB OLED

In this Insight, I set Power 2.4 as my Lum. Response Target (or gamma target). That’s because the FSI CM250 is an OLED. Since OLEDs have true blacks, their native response is a gamma 2.4 and directly plugging that in as the Lum. Response Target gets you the best results. But if you’re on an LCD? You’ll make a different choice.

 

CalMAN Studio Calibration Standard for RGB OLED in Rec 709
These are the calibration settings used in this Insight for FSI’s CM250, an RGB OLED.

Calibration Settings for a typical LCD

If your Reference Display is an LCD then you’ll modify your settings. You’ll use the standard D65 white point. And you’ll use the BT.1886 Lum. Response. Why BT.1886? Because LCDs don’t have pure blacks and the 2.4 Power setting will compromise your calibration. Instead, BT.1886 allows the calibration software to measure how ‘bright’ the blacks on your display are – and then modify the gamma response of the calibration to fit your specific display.

CalMAN Studio Calibration Standard for LCDs in Rec 709
These are the calibration settings you typically use for an LCD reference display.

What about the Input Signal Levels?

Should you choose SMPTE (64-940) or Full (0-1023)? The answer is simple: This setting needs to match whatever your reference display is set. For most of you, SMPTE is the correct answer. BUT, not always. Check with your display manufacturer if you’re unsure. Also, the 3D Color Cube workflow in CalMAN has a test to help you determine if you’ve made the correct selection.

Coming Up in Part 3 of this Calibration Series

In the next Insight, we compare the two different calibrations we did in this Insight… and then kick it up by adding a 1D LUT to our calibration and see if it improves our already excellent results!

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Comments

14 thoughts on “Creating A Calibration 3D LUT in CalMAN”

  1. Hi Patrick,
    I have a Fsi CM250 and a i1display pro with offset. I don’t understand how to replicate 1D and 3D lut workflows in LS CMS. Can you please cover this when you will talk about “calibration with Lightspace”? Thank you.

    I’ve got also some questions about LightSpace CMS:
    – If I enable the Limit Luminance function to max 100 nits, in convert color space tab, should I have to follow the “changing luminance” procedure before calibration in any case? Furthermore, If I change the luminance before characterization, should I have to use the Limit Luminance function to 100nits?
    – If I change the luminance in CM250 before the characterization, should I have to keep this new luminance value after the calibration, or should I have to reset it to Luminance Standard Mode (100 nits)?

    1. When putting this series together I had to decide if I’d show a concept, then show how to execute that concept in both apps? Or if I’d create two ‘stand alone’ series that doesn’t require a LS user to watch the calman stuff (and reverse). I’ve opted for the latter. So everything you see me doing in this series in CalMAN will be completely covered in LightSpace… and that includes the 1D + 3D LUT workflow.

      – RE: Adjusting Luminance before characterization – This is always a good idea. Remember, calibration requires you take the energy of peak white and steal from it to balance the RGB response throughout the grayscale. By setting your peak white to a brighter value than your target, you’ve got the energy to steal from for calibration. And LightSpace’s ‘limit luminance’ does a good job of also hitting your target nit value IF your display is running brighter than the target before characterization. If it’s not then you don’t want to use that option.

      – RE: Adjusting Luminace after characterization – If after characterizing and uploading your LUT you find your FSI display is running too bright, then keep the Luminance in Custom Mode and adjust down the setting until it hits your target nit value. As long as you’re using the Custom Mode in the Color Management settings, it will not throw off you calibration at all (a benefit of using an OLED).

  2. Hi Patrick thanks for bring light to the dark matter of calibration world !

    I have a questino for you: If my reference monitor is a FSI OLED CM 250 and my client monitor is a LG OLED 65EF9500, Do I need to use the OLED Judd Modified or just keep the white point to OLED ?

  3. Hi Patrick, thanks a lot for the series of insight on calibration. It would be beneficial if you can cover calibrating HDR monitors, both, for Dolby Vision and HDR10.

  4. This is a really great guide! I can’t explain how useful this has been!

    One question. I’m calibrating a monitor that can’t take a 3D LUT. So I’m putting the lut in resolve as a video monitor lut. As far as I can tell, there’s no way to then profile the display with that Lut applied. So I can’t measure how accurate or not the calibration has been.

    Is there any way of doing this?

    Thanks!

  5. Hi Patrick, why wouldn’t you first optimise the display and create a 3d lut on top of that? Wouldn’t that give better results? Why not balance the rgb gain first and then let it create a 3d Lut? Do you also check for the contrast and brightness ajustment everytime you calibrate or once you’ve set those with the test images you’ll leave them? Also, do you only set contrast and brightness level with the test images or is there a more accurate way to set contrast and brightness?

    1. Because the LUT is more accurate, doing the same thing as RGB balance but at a much more granular level.

      RE: Setting Brightness – I always check it post-calibration, since the fixes that a calibration performs will effect your peak target. And the most accurate way to set peak whites is with test patches and a meter. Later in this series I talk about specialty test images that finds mismatches between Video / RGB settings in the image monitoring pipeline.

      1. But if you put the display with rgb controls in the ballpark of where it needs to be, for instance like you did with the 2 point calibration on the Sony PVM, doesn’t the 3dlut have “less work” to do and isn’t that better? I don’t mean to come off arrogant, I’m really new to calibration and am just questioning this because I really want to understand it.

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