Getting Started with Lightspace DPS – Do You Need To Calibrate?

May 18, 2016

'Does my color correction display need recalibration?' Getting Started with Lightspace DPS (a free app) helps you answer that question.


Series

Part 1: Does This Display Need Recalibration (and a contest)?

This Insight is Part 2 of our Display Profiling 101 series (the introductory Insight is here). This Video Insight is Part 1 of our Getting Started with Lightspace DPS overview. You’ll be walked step-by-step through:

  • Activating and turning the Demo License of Lightspace into the free Lightspace DPS
  • Getting Lightspace DPS and DaVinci Resolve to communicate over your local area network
  • Understanding the ‘Calibration Interface’ menu and its ‘Quick Profile’ menu
  • A reading of the ‘Delta E’ report and what it’s telling us about the display I profiled
  • How to save your Display Profile Report as a PDF

By the time we’re done, you’ll have a basic understanding of how to use Lightspace to answer the question: “Does my reference display need to be recalibrated?”

In this Insight, I make a critical mistake while Profiling.

Go ahead and download this PDF, which is an export of my Display Profile Report:

Where did Patrick go wrong: ‘ML 001 Test Profile’ PDF

On the Grayscale Delta E graph you’ll notice a big bump from .1 – .6 in the grayscale, with my Delta E exceeding 4.0 on the 1976 line. Even the perceptually modified 2000 Delta E chart shows values well beyond 3.0.

The Delta E graph from Patrick's initial profile
The Delta E graph from Patrick’s initial profile. Download the PDF and see if you can figure out what he did wrong?

 

Since Delta E 2.3 is the Just Noticeable Difference line, this report is worrisome

The black line is the threshold above which error values are noticeable. This graph is telling us that colors on this display are different than the colors being sent to the display! And the error range is easily seen by the human eye.

In other words, between 20% and 70% on the grayscale – this display is inaccurate

It needs to be recalibrated.

And that’s the beauty of the Delta E report – it gives us a Go / No-Go reference. The rest of the reports generated by Lightspace help us understand how the display has drifted and where specifically the problem lies.

But a closer reading of the whole report reveals:

We made a mistake!

We can’t trust these Delta E values. In fact, the mistake I made was the very first mistake I made the very first time I used Lightspace. And the moment it was pointed out to me (using this report) I slapped my forehead with a ‘Duh!’.

The problem… fixing this mistake is non-obvious. So in Part 2 of Getting Started with Lightspace DPS I’ll show you the mistake I made, why I missed it and how we fix it. You’ll also see a nifty feature of Lightspace that allows us to recalculate the Delta E graph without having to re-profile the display.

And if you follow along at home and get crazy Delta E values like me… we’ll solve those over the next two parts in this series, since you’ll probably need to fine tune your settings to get accurate results.

Contest: Where did Patrick go wrong in this Profile???

The very first person who can correctly answer (in the format listed below) in the comments, ‘Where did Patrick go wrong?’ will win a shrink-wrapped copy of  ‘The Color Correction Handbook‘. A second copy of the book will be raffled off between everyone else who answers correctly while this contest is open. This contest closes at midnight, NYC time on Monday May 16, 2016.

The answer to the ‘Where did Patrick go wrong?’ question can be found in this PDF. To win you must copy and paste the following into your comment on this post:

Question: Where did Patrick go wrong with his Profile?

Answer: (replace this text with your answer)

Supporting Graph Name:

There are two parts to this answer, and you must get both parts correct to win!

You must state (1) where the specific problem is found on the report and (2) the name of the graph that supports your answer. The time-stamp on the comments will determine the order of responses. Robbie Carman will be the final arbiter of who answered correctly, in the case of a dispute or ambiguity.

Do you already own the prize?

If you already own the Color Correction Handbook, please hold back your answer to let someone else win the prize!

I’ll announce the winner in the Comments.

Enjoy!

Next: Fixing the mistake & learning to read the graphs in Lightspace

In the next Insight in this Getting Started with Lightspace DPS series, you’ll get the answer to what I did wrong and how to fix it (and without having to re-profile the display). We’ll also go through each of the graphs that Lightspace generates to understand how to read them. Remember, the goal of this series is to get to the answer, “Does my display need to be calibrated?” These graphs are the key to understanding the answer to that question. After watching the video below, head over to Part 2.

Update 1: The rules for the contest have been modified… there will be two winners. The first person who correctly answer will win the book. A second copy will be raffled off to a second person, selected from anyone else who also answers correctly. This contest closes at midnight, Monday May 23 2016, NYC time.

-pi


Comments

26 thoughts on “Getting Started with Lightspace DPS – Do You Need To Calibrate?”

  1. Question: Where did Patrick go wrong with his Profile?

    Answer: Was his monitor at gamma 2.4 and the calibration looking for gamma 2.0?

    Supporting Graph Name:DifGamma

  2. UPDATE: There will be two winners in this contest. Winner #1 is the first person who answers correctly. Winner #2 will be randomly selected from all the other people who answered correctly before the contest close date. The contest ends midnight, NYC time on May 23 2016. I’ll announce the winners here in the comments on Tuesday, May 24, 2016.

  3. My best guess is that the target gamma is wrong.

    The report says
    Target Gamma: 2.200
    Average Gamma: 2.430

    If the target was set to 2.400 then that would actually be pretty close…

    Edit:
    Oops, I only skimmed the written part sorry

    Question: Where did Patrick go wrong with his Profile?

    Answer: The target gamma was set to 2.2 but should have been 2.4

    Supporting Graph Name: DifGamma (It’s offset by about 0.2)

    1. Hi Guy! Thanks for commenting! I’m not commenting on the substance of your answer (since the contest is still open) – but if you wish to put yourself in the running to win the book, please be sure to use the format (as specified in the ‘where did patrick go wrong’ section of this page, including your thoughts on which graph supports your Answer):

      Question: Where did Patrick go wrong with his Profile?

      Answer: (replace this text with your answer)

      Supporting Graph Name:

  4. Question: Where did Patrick go wrong with his Profile?

    Answer: Monitor set to a different Gamma than the target gamma in Lightspace calibration software.

    Supporting Graph Name: DifGamma

    (Initially thought there could have been a discrepancy in what type of monitor type (LED/phosphor) type you set in the software in relation to the monitor you used, but then saw the gamma difference.)

  5. Not entering your contest, but, wanting to ask a question. After running Lightspace CMS, and seeing some rather large delta E’s, I am surprised because the monitor was calibrated with Spectracal Calman RGB. It would seem that the Lightspace CMS disabled the .icm profile that applied the Calman corrections and did not perform the test WITH the .icm profile applied. Am I to presume that Lightspace CMS will apply the current .icm profile during the test?

    1. The workflow I’m showing in this series is for *external monitor* calibration – a monitor that would be monitored through Decklink or Ultrastudio gear. It’s a different workflow than you’d follow for computer display calibration, like you did using CalMAN RGB. I don’t want to give you the wrong answer so I’ll ask Steve from Light Illusion to drop in with an answer to your question.

      1. Thanx to both of you, Steve and Pat, for such a quick reply. I understand what you’re saying, that color accuracy from internal color management systems, like ICC or ICM, ain’t so good for color accuracy. I had forgotten that distinction between external monitors and graphic cards.

        I’ll wait for your next installment, to see what I may be missing, tho’.

    2. Hi Bill – LightSpace will not disable or apply any ICC/ICM – it will use the PC setup exactly as it is.
      But, you have to be sure the image path you are using for patch generation is also using the ICC/ICM.
      In reality, only the VCGT component of the ICC/ICM is loaded into the graphics card, and that is a 1D LUT, so will only ‘manage’ grey scale/colour balance.
      Any ‘Gamut’ control component of the ICC/ICM will only be applied IF the graphics software is ICC/ICM compliant.
      Most professional Film and TV systems avoid ICC/ICM workflows, as they are not accurate enough – and as their application can vary depending of the graphics system being used, the results are not guaranteed.

      Hope that helps.

      Steve

      1. Bill – There’s a good chance that over the next two videos I may offer a pointer or two that will help you set your colorimeter properly. In this Insight, I got terrible Delta E’s, but you’ll see in the next video how easy it is to fix the problem. In the video following that, I’ll go through the setup of an i1 Display and all the various settings, to optimize for that meter. It can be tricky – but once you learn to navigate the minefield, it makes a ton of sense and the results are accurate and replicatable.

    1. Marcus,

      Part 2 will probably be released on Tuesday. Next week there will be a Part 3 about Lightspace: Optimizing the i1 Display OEM for Lightspace, where I dig through all the settings to help you get the best readings possible. I’m also collecting tips that Steve from Light Illusion, Bram from FSI and Robbie Carman have been sending me. I’ll post those after we wrap up working in CalMAN Color Checker. I want the dust to settle and gather more questions / answers before recording that one.

  6. Going to be very specific here to increase my win chance 🙂

    Question : where did Patrick go wrong with his profile
    Answer : Before you start any profiling, you have to make sure you set all your target values properly for the colorspace and luminance range you want your monitor to be compared with.
    Now Patrick did not specificaly mention inthe video what his desired target is other then rec709 but knowing him he probably (and lets assume for the sake of this discussion) wants his monitor to match rec709 with a target gamma of 2.4 and a max nit value of 100.
    The shipped rec709 target of DPS is 2.2 , so he has to first ‘create’ a new target with rec709 and gamma 2.4 before it can be selected in the target dropdown box. The free version allows you to manualy create new targets , in this case easiest by selecting the rec706, change the gamma value to 2.4 and then save it under a new name eg [email protected]
    Now it can be selected as profiling target.
    The max nits value can and should be selected in the screen that Patrick showed us where also the probe offsets can be entered. In this case the default of 100 likely matches his desired target, but in case it does not is a potential for errors in interoreting the resulting graphs.

    Supporting graph : diff gamma , which show a 0.2 offset in the range where also the delta e shout above the desired results.

    To be completely anal retentive about the answer , he also may or may not have his momitor warmed up for some time (depending on monitor this can take a bit longer but a good starting point of at least 30 minutes works for my monitor), prior to starting the calibration. But looking at the result, that would be a seriuously bad monitor if just not beeing warmed up gives him this result. So his main error is as mention above.

    P.s. Unfortunately in the free version of DPS this custom [email protected] target can not be saved permanently and every time you run the program you have to redo it. Has to become muscle memory 🙂
    I have made this mistake too many times myself unfortunately while in the long learning process of monitor profiling and ultimately calibration.

    Edit:
    Alternative answer : he did not make a mistake but just on purpose did this to make us think about the process and better understand the insight. As this is one of his typical teaching methods , he is not beyond suspicion and a case could be made if it came to a supreme court session.

    1. Actually…
      Before you start any profiling, you have to make sure you set all your target values properly…

      With LightSpace CMS that is not true… you can chnage your ‘target’ values at any time – before.during/after profiling.

      Profiling is just taking measurements of what the display is presently set to – there is no need to have anything pre-set.

      And further, the Min/Max ‘Luminance Units’ values set via ‘Options’ have no impact on the graphs. The values for the graphs are taken directly from the profile data, after the profile is complete. The ‘Luminance Units’ are only used to set the ‘Target’ values when performing ‘Manual Measurements’, used when manually setting a display’s own controls, and to set the ‘min/max limits’ of the ‘Thermometer’ display, also used when taking manual measurements.

      Steve

      1. Sure, you can change a lot after the actual measurement, but normal workflow would be to do that first to prevent errors like Patrick made. If you set it first you basicaly set you mind in how you interpret the results.
        Tnx for the info on the luminance values. That i did not know. I would have sworn that it would change the delta if you set it at 500 while you monitor is calibrated for 100. You learn something everyday 🙂
        I still set it anyway. Good habits and there is no real workflow logical reason not to do it 🙂 (specially if you use and compare different types of calbration software that may be less forgiving as yours 😉

        1. Good Practice is always GOOD!
          Makes sense to always set all values as they should be regardless, as you may go back to a function that does use those values and forget you have not pre-set them.

          Oh – and in the pre-set colour space EBU TECH 3320 is ‘Rec709 Gamma 2.4’.
          You do not need to make a new Rec709 2.4 gamma one.
          We have kept Rec709 as 2.2 Gamma as this is historically what is most common – BUT Rec709 actually has no
          defined gamma…
          The EBU spec does specify 2.4 gamma now – they changed to be ‘closer’ to BT1886.

          Steve

      2. Hi Steve (again),

        I just did a quick test as this max nit value sat wrong in my personal experience and now i know why. You are right (of course as you made it that the graphs do not change) but i would still stick with my recommendation to set it properly. During the automatic measurement you can see realtime what the delta E values are and where it (as well as the the L/U/V values) deviates (and how much) from the set target. (like you mentioned as well , the ‘thermomenter values’)
        This “does” show different values depending on your set nit . I set the max nit to 500 as a test just to see exaggerated results and the real-time displayed delta-e values shoot through the roof (double digits).
        I find the realtime info next to the graphs (main source of info) of good value to see during your measurement where it goes wrong and in which area the most issue are .

    2. Glenn – Indeed. If I thought a trick answer would be more valuable than an actual mistake… I’d do it! But in this case, I’ve just replicated the very first mistake I made with Lightspace 🙂 Figuring out the answer to the mistake was a very valuable lesson in how to use this app… so I thought it’d let everyone join in the fun!

      Thanks for your detailed response here. I greatly appreciate your enthusiastic participation!

  7. Just posted an extensive reply with apparently the correct answer as Patricks spam/moderation filter marked my reply as spam/awaiting moderation. Guess he put in a filter to capture any correct answers so he does not have to shell out for the price 😉

      1. Tnx sensei. Reading it back i see one specific (irony intended) word that likely triggered your fence to come down as it is often used in different target group one on one tutorials to say it very carefully 🙂

  8. We have a Winner (actually, two Winners)!

    As per the rules above, the first person to get the answer correct – and in the format as required by the rules – is Greg Greenhaw!

    The second winner, randomly chosen from between everyone else who answered correctly – and in the format required – is Guy!

    I’ll contact each of you for your shipping addresses for your copy of Alexis Van Hurkman’s ‘Color Correction Handbook, 2nd Edition’.

    Most everyone got the answer correct: There was a mismatch between the Target Gamma and the Measured Gamma; gamma 2.2 vs gamma 2.4.

    In my mind, the graph that showed this most clearly was the Gamma graph – but I accept the Diff Gamma graph as an acceptable alternate indication that the problem lies within the gamma profile of the display.

    In Part 2 of this series on ‘Getting Started with Lightspace DPS’, we’ll go through this much more thoroughly.

    Congrats to the Winners and thank you all for answering and participating.

  9. great series!

    I wonder, when profiling my display, should I use Video Levels or Full Levels ?
    I noticed that when I used Video levels the color values of the patch shift between light space and davinci. and in the video it was said to look for consistency in Color values.

    Thanks

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