ColourSpace uses a Sub-Range approach to patch scaling, which means it will define the output patch triplet values based on the patch scale range set within the Settings menu.
Resolution sets the Bit Depth used to define patch values within Manual Measure, and the bit depth sent to external TPGs, depending on their capabilities.
User defined .csv Patch Lists generate output triplet values that directly match the values in the .csv file
Patch Scale and Resolution must be set to match the Patch List data
Patch Scale & Resolution Settings
The Patch Scale options set the range between which the patch triplet values, sent to any attached Test Patch Generator, will be restricted to, and needs to match the display's setting for input video range. This is usually Full for PC displays, and Legal for TVs, with Extended specified for 109% super white, as sometimes used in post-production workflows.
The Resolution option sets the bit depth used to define the patch colour within the Manual Measure menu of ColourSpace. Any TPG attached to ColourSpace will be sent patch triplet values in the bit depth required by the TPG, based on the Resolution value setting. Setting the Resolution value within ColourSpace to match that of the TPG's expected input triplet bit depth is therefore the expected configuration.
Using a higher Resolution bit depth will not increase calibration accuracy
Greater bit depth need only be used when matching a TV's CMS control points during Manual Measure adjustment, when the control points are specified in 10 bit, or greater, values
Manual Measure Sliders
The range the manual Measure Sliders work to is defined by the Patch Scale values set within Settings, and will limit the sliders to just the set range. If Legal is set as the Patch Scale values, the sliders will not go beyond those values. For example, setting Limited range (8 bit) will prevent the sliders from going below 16, or above 235.
The displayed patch bit depth is defined by the selected Resolution value. When changing Resolution bit depth, the patch values are absolute, so if a 235 (8 bit) patch is displayed, and the Resolution is changed to 10 bit, the patch displayed will remain as 235, but now as a 10 bit patch colour, so will be considerably darker.
Resolution bit depth should be set to match the display's bit depth, and that of the TPG being used. Setting to higher values will not increase calibration accuracy, and may cause less accuracy due to a miss-match between the value defined within ColourSpace, and the actual patch value displayed and measured on the display screen.
The presets held within the Characterisation menu, including Cube based and Quick Profiles, are automatically set to the range defined by the Patch Scale values set within Settings.
Patch Resolution is defined in floating point within ColourSpace, so the selected Resolution bit depth is irrelevant when performing Characterisation profiling, other than matching the signal expected by the TPG and display, as required.
User Characterisation Patch Lists
User generated .csv Characterisation Patch Lists need to match the Patch Scale setting defined within the ColourSpace Settings menu - Legal, Extended, or Full, as well as define the patch triplet values in the correct Resolution bit depth, to guarantee expected profile results.
Patch Lists must match the Patch Scale and Resolution bit depth selected
If there is a mismatch, profile results will be inaccurate.
Patch Lists must have black and white patches that match the Patch Scale range
If the patch list lacks black and/or white patches for the selected Patch Scale, synthetic black/white data will be added to the profile when Saved, based on the Target Min/Max Luma values in the Settings window.
0 and 255 for Full; 16 - 235 for Legal; 16 - 235 & 255 for Extended (8 bit)
User Preset Patch Lists
User generated .csv Preset Patch Lists should match the Patch Scale setting defined within the ColourSpace Settings menu - Legal, Extended, or Full, to guarantee expected operation.
If the .csv patch list has values that go above/below the range set via Patch Scale, the triplet output will be clipped to the set Patch Scale range, with all patches below/above the set range generating the same output triplet value.
if the patch list lacks black and/or white patches for the selected Patch Scale (e.g. the patch list is Legal, but Patch Scale is set to Full) synthetic black/white data will be added to the profile, based on the Target Min/Max Luma values in the Settings window.
The patch data displayed below the Patch Colour box will shows the actual triplet to be used, and hovering over the patch within the patch list will show both the clipped patch patch triplet value, and the original patch value, with a highlight around the patch, and a **CLIPPED FROM** warning.
When performing an Auto Advance sequence, the highlighted patch being measured will start and stop with the min/max patches that match the set Patch Scale, not the min/max patches within the patch list, if they go below/above the values set via Patch Scale.
Note: If a user generated Preset Patch List, with Full range values, is loaded into Characterisation, Custom Sequences, and re-Exported with Patch Scale set to a different range, for example, Legal, the exported patch set will will be clipped, as defined above.
The Resolution bit depth set within ColourSpace should also be matched by the .csv triplet values, as the patch values are absolute.
If a .csv patch list with 8 bit Legal Patch Scale values is used when Resolution is set to 10 bit, or higher, the peak patch level will be limited to 235 (at the set bit depth), and will be darker than expected.
109% Extended Range
The concept of calibrating a display to 109%, extended range, to allow for super white, is not something that should be required for home TV calibration, as no broadcast material exceeds Legal range.
However, for post-production, 109% Extended Range is a valid concept, and needs to be understood with respect to Patch Scale.
When calibrating to 109% Extended Range, patch 235 (8 bit) should target 100 nits (for a Rec709 grading display), with patch 255 (8 bit) being 9% over-range. The luma value for patch 255 (8 bit) will vary depending on the target colour space EOTF, as well as the display's black level.
With ColourSpace, when working with 109% Extended range, the 100% patch (235 - 8 bit) is the target Peak White value.
ColourSpace always works 0% - 100% range, with 109% being over-range
The 1D graphs will plot the 0-100% range, with 109% plotted over-range.
To see over-range data, the graphs will need to be zoomed-out.
Limit Range limits the patch range such that the defined nits value becomes the peak of the measured range, within the selected Patch Scale range.
If using Manual Measure, the sliders will be restricted to the set maximum value.
If a user defined Preset patch list is used, any patches over the set Limit Range value will be clipped, both in Manual Measure, and Characterisation.
When using ColourSpace's in-built patch sets within Characterisation, the whole patch range is re-scaled to fit within the defined Limit Range value.
Regardless of the method used to display the patches, the saved profile will plot the measured range within the defined Patch Scale, with the 1D graphs, such as EOTF, showing just measured range.
The above graphs show a pre-calibrated PQ ST2084 preview display, with a max peak luma of 280 nits. After profiling with a Limit Range value of 157 (8 bit), the first graph shows the profiled 280 nits range plotted within the full PQ ST2084 10,000 nits, while the second graph shows the same profile plotted against a PQ ST2084 colour space set to 280 nits peak.
Critically, the Limited Range profile can be used to generate a calibration LUT, making it possible to profile a PQ based HDR display, with a burnt-in PQ EOTF active, and generate a more accurate calibration. No requirement to be forced to disable the PQ EOTF and replace with a pure power law EOTF.
The in-built Test Patterns also follow the Patch Scale settings, with their signal range set to match the Patch Scale values. It is therefore important the correct Patch Scale values are defined, to match the display's input signal requirements, when using the Brightness and Contrast Test Patterns to set black and white clipping points, etc.
With Patch Scale set to Legal, the Brightness Test Patch is lifted, such that zero black becomes 16 (8 bit), and the Contrast Test Pattern is lowered, such that 100% white becomes 235 (8 bit).
With the correct Patch Scale settings, the Brightness and Contrast Test Patterns will look identical on Full Range, and Legal Range displays, enabling correct configuration.
Mixing Profiles & Patch Scale Settings
Changing the Patch Scale setting for any given profile, after profiling or after recalling a profile from the library, will invalid the profile data displayed.
ColourSpace will faithfully display the profile data, as constrained by the Patch Scale settings, but having a mismatch will make the displayed data invalid.
All profile data is only valid when displayed with the correct Patch Scale settings.
The Patch Scale setting must match the Profile
If there is a mismatch, the displayed profile data will be invalid.
Profile data is only valid when displayed with the correct Patch Scale settings
Point Info Dialogue
The Point Info pop-up dialogue window is also constrained by the Patch Scale value settings, as the actual data in the profile is floating point, so normalised between 0-1.
Therefore, to see the actual point info as originally saved into the profile, the Patch Scale settings must be as set when the profile was made.
If the Patch Scale values are set differently, the point info triplet data will be re-scaled to match the selected range, maintaining the actual measured data relationship for graphing. This can, and will, result in invalid point data.
The Resolution bit depth also constrains the data displayed in the Point Info dialogue, and should ideally use the same Resolution value as used when the profile was generated, to see the point info as originally saved into the profile.
The above shows a 10 bit, 1 LSB step, profile, displayed with Resolution set alternatively to to 8 bit, and 10 bit. When set to 8 bit, blocks of 4 input patches all map to the same output patch number, as is expected.
Test Patch Generators
External Test Patch Generators, and TPGs built into displays, display the RGB triplet value, as specified within ColourSpace. The correct Patch Scale and Resolution bit depth settings depend on the TPG itself, as well as the display's own capabilities/settings.
When connected to an external TPG, be that a stand alone TPG, LUT Box with TPG capability, or display with in-built TPG, ColourSpace will send the correct triplet value, based on the hardware's specific capabilities.
It most instances, this means the Resolution bit depth set within ColourSpace is irrelevant, as any set value is defined in float, before be converted into the correct triplet integer for the TPG in use.
For most applications, 8 bit Resolution will be the default setting.
If the Resolution is set to a bit depth greater than the TPG's/display's capabilities, capabilities there is the potential for duplicate patches being sent, slowing profiling unnecessarily.
If the display's screen has a bit depth that is lower than the input signal it accepts, there will also be flat spots on the profile data, if the number of patches exceeds the screen's native bit depth.
See the dedicated User Guides for each supported external TPG, LUT Box, and display.
BG Colour, Stabilisation, & Drift
After setting Patch Scale, BG Colour, Stabilisation, & Drift can be set to alternate colour values that can be beyond the Patch Scale limits, such as placing the BG colour to zero, with Patch Scale minimum set to 16 (8 bit).
(BG Colour, Stabilisation, and Drift patches are always set via 8 bit values)
Direct HDMI Profiling
This simplest method for Test Patch Generation is to use the direct HDMI output from the ColourSpace PC. This can provide bit perfect patch generation, without the need for any additional hardware.
An in-depth User Guide can be found on the Direct Profiling page.