The below article contains excerpts from The Display Calibration Guide – Volume 1 SDR.
Setting Up Automatic Pattern Generator for HDMI from a Laptop
You should set the following up to display patterns from a computer:
- Connect an HDMI cable to your laptop or desktop PC
- Go into Windows Display Preferences and make sure toExtend the main display as opposed to Duplicate it.
- Go into Pattern Generator Preferences in HCFR and selectyour target screen, which will be the second from thedropdown (even though it might have the same name)
- Set image area according to display type (see previoussection on this)
- Leave APL at 0
- Set Pattern Intensity to 100% for now (this will need tochange for CMS only)
- Set Pattern Generator to GDI (fullscreen)
- Set 0 – 255 for GDI options. This is normally the correct setting but see section on Internal vs External Patterns for more information on this option.
- Tick “disable video LUT”
- Click OK to save and exit.
Advanced Automatic Pattern Generator Options
There are two tabs when configuring Automatic Pattern Generation. The Blanking tab allows you to set the main display to a black screen when calibrating so it doesn’t interfere with the measurements. For this to work, your HCFR screen and your calibrated display cannot be the same (e.g. don’t set this if you are calibrating your laptop’s screen while running HCFR on the same laptop.)
The Display tab allows you to set the following options:
- Target screen: which screen to display the patterns on.Is it your primary screen or another screen that’s connected? When using internal patterns, configure the display for extended mode in your Windows Display Preferences and then select the secondary screen here (it may also only show up as a Generic PnP Monitor.)
- Image area (%): You can set up the patten size on the display as % of display area.
- APL (video) level (%): this is the average picture level displayed on the rest of the screen when using window patterns. This is helpful if you can’t defeat the display’s (local) dimming algorithm in the display’s menu. This can stop the display from dimming when displaying dark patterns as the overall APL is kept the same. This is normally an issue on high-end LCDs such as QLEDs.
- Image Background: instead of displaying black or another APL around the window, you can display an image in the background. Again, this might be helpful if certain dimming algorithms are non-deflatable on the display.
- Pattern Intensity (%): how bright you want your patternsto be as a % of full white. This is normally 100% for greyscale and gamma and should be set differently for CMS (75% or 50% dependent on SDR / HDR and type of display). We discuss this under CMS.
- Pattern offsets from centre (pixels): This option is only available when using ChromeCast or PGenerator (more on these in a moment). If using window patterns, you can specify them to be offset from the centre. This is useful if you cannot get the sensor to line up with the centre of the screen. Be mindful that some displays will have lower contrast and colour / gamma characteristics towards the edges and corners so it is not a great idea to calibrate from the edge or corner of the screen.
- Display Mode :
- GDI fullscreen: use the inbuilt pattern generator overyour laptop / PC’s external display port / HDMI port.
- GDI (overlay): same as above but in a maximisedwindow as opposed to full-screen.
- Floating window: same as above but in a smallerwindow you can resize.
- CCast: Use a Chromecast connected to the samenetwork as your PC.
- Raspberry Pi: use a PGenerator (link) on Raspberry Pi.
- madTPG: use MadTPG installed on your PC. MadTPGis MadVR’s pattern generator. You can optionally disable the calibration loaded into MadVR (3DLUT and LUT).
- Display Triplets: this displays the pattern code (called the triplet) on the bottom of the pattern. It is not normally necessary to do this. It may only display on GDI patterns or PGenerator.
- Enable HDR10: Make your Nvidia graphics card to inject HDR10 meta-data into the HDMI feed without switching Windows into HDR10 mode which would mess up the patterns. The patterns will still be in an SDR container but with the correct meta-data to force the display into HDR10 mode. This allows you not to have to use an HDFury device to inject the meta-data. However, please note that newer versions of Windows 10 and Windows 11 break this option by switching Windows 10 into HDR mode.
- GDI Options: these are to configure the inbuilt patterns using GDI – over your secondary display connection for example.
- 0-255: These options are for the video levels discussed earlier in this guide. 0-255 is full range / enhanced and it is what PCs put out. But this is the default correct option when the display and Windows are in limited range.
- 16-235: this is for video levels that Blu Ray players out out. Unfortunately, sometimes enabling this does not have the desired effect unless other options are correctly set. See further on in the Internal vs External Patterns section to configure this correctly.
- Disable video LUT: this option disables any monitor calibration loaded for the display in Windows during pattern playback.
Recommended Patch Sizes
We normally recommend using window-ed patches with flat panels (e.g. 10% window size is standard). With projectors, I recommend you use full-screen patches.
However, you need to be aware of how different window sizes affect brightness of a patch (and therefore both greyscale and gamma) – especially with HDR on some displays. This is normally due to power delivery within the display directing more power to smaller bright areas than larger bright areas – either because of technical or regulatory issues.
In addition, some displays such as OLEDs will engage brightness limiters for larger window sizes and can even drift during calibration if patches are displayed continuously. To combat this, you can use even smaller window sizes (e.g. 5%) and put up a black frame every so often to let the display rest. Automatic pattern generators are normally able to do this (including HCFR’s Automatical pattern generator).
Recommended Patch Intensities
The following are the recommended patch intensities when calibrating:
Greyscale (SDR/HDR): 100%
Gamma (SDR/HDR): 100%
CMS (SDR): 75% (50% for WRGB OLED and DLP) CMS (HDR): 50% – corresponding to approx. 100nits / reference white (observe especially with limited luminance displays such as projectors!!!)
The reason we recommend lower intensity patterns to be used for CMS calibration is that there is very little information at the edge of the gamuts and especially at 100% intensity.
Therefore, it is better to optimise the display for lower intensities where most of the content lies. In addition, some display technologies like WRGB OLED or single-chip DLP are not accurate at higher light intensities, therefore calibrating them at that intensity will compromise the gamut at lower intensities.
While this might not be obvious, frame-rates at which you are displaying patterns and patches does matter.
This is because both source devices such as Blu Ray players and streaming boxes, as well as displays can process data differently when put into 24Hz versus 50 or 60Hz modes. This is why it is important to prioritise the frame-rate that you will be using the most.
For example, if your calibration is for your games console, such as a Playstation or an Xbox, you may want to prioritise 60Hz output as the consoles will generally be connected at this framerate (even if the games are running at 30fps btw).
If you are calibrating your display to watch movies and TV shows and you have your Blu Ray player or Apple TV set to 24p (or frame-rate matching) output, then it is a good idea to run the patterns at 24Hz. This will ensure that your calibration is going to be correct when you put on a movie.
The Display Calibration Guide
If you would like to learn more about displays, and display calibration, you can get The Display calibration Guide here.
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