Test Patch Generation

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.


Patch Scale 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 need to match the display's setting for input video range. This is usually 0-255 for Full Range displays, and 16-235 for TV Legal, although any range can be specified, such as 16-255 for 109% super white.

Patch Scale

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 16-235 is set as the Patch Scale values, the sliders will not go beyond those values, with 0% Black being defined as 16,16,16, and 100% white as 235,235,235.

Characterisation Presets

The presets held with the Characterisation menu, including Cube based profiles, are automatically set to the range defined by the Patch Scale values set within Settings.

Preset Patch Lists

User generated .csv Preset Patch Lists should ideally match the Patch Scale values set within Settings, to guarantee expected operation.

However, if the .csv patch list has values that go above/below the values 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.

Additionally, the patch data displayed below the Patch Colour box will show the actual triplet to be used, while hovering over the patch within the patch list will show the actual patch value, for those patches that are below/above the values set via Patch Scale.

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.

If a user generated Preset Patch List with a 0-255 range is loaded into Characterisation, Custom Sequences, and re-Exported with Patch Scale set to a different range, for example 16-235, the exported patch set will will be 'clipped', as defined above.

Test Patterns

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.

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 16-235 range.

However, for post-production, Extended Range, 109%, is a valid concept, and needs to be understood with respect to Patch Scale.

When calibrating to 109%, Extended Range, patch 235 should target 100 nits (for a Rec709 grading display), with patch 255 being 9% over-range. The Luma target for patch 255 will vary depending on the target colour space EOTF, as well as the display's black level.

For a display with a zero black level, the 109%, patch 255 Luma target would be:

  • Rec709, EOFT 2.4 - 123.336 nits
  • Rec709/sRGB, EOTF 2.2 - 121.199 nits
  • P3 D65, EOTF 2.6 - 125.510 nits

The EOTF value is all that changes the 109% target nits value, if the display's black remains at zero. If the display's black level changes, so will the 109%, 255 patch, Luma target nits value. BT1886, with a non-zero display black level will be different again.

With ColourSpace, to calibrate to 109%, select 16-255 as the Patch Scale, and within Manual Measure, measure the display's black and white levels. Set the sliders to patch 235, and read the Target Y value. Adjust the Luma Target (Nits) value within Settings until the Target Y in Manual Measure matches 100 nits. The Target Max Luma is now set correctly for 109% Extended Range.

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 should 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.

BG Colour, Stabilisation, & Drift

As Patch Scale is a global setting, BG Colour, Stabilisation, & Drift will also initially be constrained by the set Patch Sales values. If it is desired to used alternate colour values, such as placing the BG colour to zero, with Patch Scale minimum set to 16, the BG Colour can be re-set after Patch Scale has been set.

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.

Test Patch Generators

External Test Patch Generators display the RGB triplet value, as specified within ColourSpace.

See the dedicated User Guides for each supported external TPG, LUT Box, and display.

Direct Profiling

HDMI Profiling