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Revisiting Judd Modification For OLEDs

January 20, 2018

Team Mixing Light answers a member question about using the Judd Modification for an OLED reference monitor. What is it? When to use it?


Series
Day 20: 24 Insights in 24 Days – 2018 New Year Marathon

Team Mixing Light Note: Patrick was scheduled to release the next Insight in his CalMan calibration series today. He was going to show you how to calibrate a Sony OLED without the use of LUTs. Instead, he scheduled the installers for overhead speakers as he finishes upgrading his home theater to Dobly Vision with Dolby Atmos (a 5.1.2 system). So we’re releasing this Mailbag today. Tomorrow Patrick will release his calibration Insight (or he’ll be fired ūüôā )


‘What Is The Judd Offset And Should I Be Using It?’

We’re in the final week of Insights Marathon!¬† We hope you’ve been enjoying the articles, videos, and podcasts so far.¬†In this installment of¬†From The MailBag, we got a question from Mixing Light member Manuel who asks:

‘I have an FSI AM250 OLED monitor and I noticed in the color management menu with color matching parameter I can choose between CIE 1931 and Judd Modified.¬† Which one should I be using?¬† I’ve read about Judd modification, but I don’t fully understand it.’¬†

Great question!  And one that we get quite often from members, or get asked about at conferences & events.

The use of a Judd white point has become a common practice with RGB top emission OLEDs over the past few years Рbut why? Is it just a white point adjustment?  Should you be using with your WRGB OLED? Team Mixing Light discusses this and hopefully clarifies a few things for Manuel.

Note: As we roll into the last week of our 2018¬†Insights¬†Marathon, a reminder that the week of January 29th, 2018 – February 2nd, 2018 we’ll be off.¬† Our regular schedule of¬†Insights¬†will pick back up the week of February 5th and at that time, we’ll start releasing MailBags weekly and roll out a couple new features too!

Remember, you can submit your questions via the contact form or by emailing us at [email protected] Your questions can be technical, creative, about gear or anything else related¬†to the world of color correction.

Postscript:  A few things worth mentioning or clarifying from this installment of From The MailBag

  1. When Sony first introduced their OLED, they were originally shipped with a CIE 1931 white point. About 18 months after release, Sony started shipping them with a Judd Modified white point.
  2. As mentioned in the episode, the Judd Modification is known as a CMF or Color Matching Function. One way CMFs can be used is as an offset on a calibration meter. The problem with this approach is that when used on a calibration meter the entire Judd Modification¬†is used and not just white balance is being affected. Don’t do this!¬† As we say several times in the episode, Judd in practice is a white point adjustment only.
  3. While metamerism and OLEDs are often talked about together, it’s important to understand that metamerism¬†can happen with any differing display technologies and is a phenomenon not specific to OLEDs matching other displays.

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3 thoughts on “Revisiting Judd Modification For OLEDs”

  1. Hey Robbie, now that you are rocking 4 displays on your suite due to HDR, how did your calibration approach change, if at all? Do you experience a metarism failure between the x300 and the FSI? What about your 2 client monitors? Do you use your x300 for sdr work?

    1. Hey Jose –

      Sorry for the delay getting back to you on this – I’ve been in NAB recovery mode ūüôā

      So I don’t actually use all 4 displays – the SDR LG OLED setup in the room was simply for an event we did with Dolby.

      The X300 and the DM250 are both top emission RGB panels and have nearly identical SPDs. Rather then doing any sort of perceptual match routine all I’ve done on the DM250 to match the X300 is dial in a couple points of Blue in the FSI white balance controls – as the DM250 is older and Blue ages quicker this makes sense. But even with out that adjustment these displays match well.

      Of course one is showing P3/2020 PQ and the other Rec709 Gamma 2.4 but from a white balance point of view (which effects perceptual ‘matching’ the the most they’re pretty much identical)

      The LG client monitor in SDR and HDR is a whole another story. With that I’ve done a perceptual match routine (discussed here on ML) for SDR and HDR matching to the X300. SDR is easy, but in HDR the LGs are really inconsistent – panel heats up and at high nit patches things are never really the same twice! It takes a lot of patience to get a quality HDR calibration.

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