Home Cinema

Using LightSpace for Home Cinema

Unlike existing traditional consumer calibration systems LightSpace HTL & HTP are not limited or cut-down versions, and instead are exactly the same as used within the professional market for high-end colour management - no compromises.

This makes LightSpace HTL & HTP the best possible calibration systems for use in any AV environment, be it home use, educational facilities, corporate, or entertainment. Knowing you are using the exact same system as used in professional post-production facilities, where the master film and TV programs are graded, guarantees the images seen on AV system will match perfectly the look intended by the program's production team.

As this is the basic intent for any calibration process - to match as accurately as possible the original source content as graded - the results attained by LightSpace CMS are impossible to match through the use of existing traditional consumer calibration systems.

Ease of use, with automated profiling and 3D LUT generation, enables system integrators and home users to master advanced calibration with ease, quickly guaranteeing the best possible end result.

True 3D LUT Calibration

LightSpace CMS Home Cinema Calibration

LightSpace CMS works with true 3D colour management, both for profiling and final calibration, based around an unmatched 3D colour mathematics engine for uncompromised final calibration.

Some alternative calibration systems that have evolved from home use applications have attempted to adopt 3D colour management based workflows, but lack the advanced colour mathematics required for true and accurate operation. This results in a 'guess-work' based approach to calibration that inevitably produces inferior final results.

There is also no need to profile with a 3D cube to then be able to generate true 3D LUT for calibration. If you have a perfect display (ideally with near perfect RGB Separation and good RGB Balance) you can actually profile just the grey scale and single R, G, B patches, and then generate a perfect 3D LUT that would control not just the grey scale, but gamut as well. Very, very few calibration system understand this fact.

But, different displays do have different requirements for profiling, and one approach will not work across the board. For displays that have a linear response, with a good level of RGB Separation (RGB decoupling) and reasonable RGB Balance (white point) a Quick Profile approach will work, while for displays that are non-linear, with poor RGB Separation and poor RGB Balance full 3D cube profiling will be required. Additionally, the number of points used within the 3D cube profiling data set is key to getting a final accurate calibration.

Alternative systems that use a guess-work approach to calibration will struggle to generate the necessary accuracy, as the number of points measured are too few, and too spaced apart, and combine profiling with calibration which is not an ideal approach as it locks the profiling to the expected end colour space (gamma and gamut). For further info on this see later.

If the profile has the correct number of points for the display's needs, and that can mean using a minimum of a 17 point cube (17x17x17 cube), a 21 point cube (21x21x21) for a display with poor RGB Separation, RGB Balance and/or low gamut, a final calibration LUT can be generated that has a smaller number of points, but that retains the inherent accuracy of the higher resolution of the profile.

When profiling with a small number of points it is virtually impossible to generate a calibration LUT that will be anywhere near accurate enough.

An example of this is the use of 125 point 3D cube calibration performed by some alternative systems. What 125 point calibration actually means is a 3D cube that is 5x5x5 points. For combined profiling and calibration this is no where near accurate enough.

However, a 5x5x5 calibration LUT can be accurate for final use, when combined with a higher resolution 1D LUT for grey scale management, if the initial 3D cube based profiling was done at a much higher resolution than the final LUT resolution - which is why a minimum of a 17^3 profile is really needed for accurate profiling.

Note: This is not the same as using fewer points initially, and interpolating the final results - that will never give as accurate end results.

The smaller Lumagen Radiance LUT boxes are an example of this, where a 21 step 1D LUT is use for grey scale management, in combination with a 5 point 3D LUT for colour management, which can produce good results when the initial profiling is performed with a higher resolution cube.

5x5x5 Cube 17x17x17 Cube

The above images show a 5x5x5 cube, as used to perform 3D cube profiling by many alternative calibration systems, compared to a 17x17x17 cube, as used by LightSpace CMS for profiling. The difference in profiling accuracy is obvious to see. With LightSpace's ability to use 21x21x21 (or greater) cubes the difference is yet more obvious.

The following images show the difference this makes in a real-world situation.

5x5x5 Cube 17x17x17 Cube

The above LUT for a real display shows the calibration accuracy in 5x5x5 and 17x17x17 data. The complex nature of the calibration is due to the display having a very non-linear RGB response, which is common for many home TV displays. From the above comparison it is easy to see how the 5x5x5 cube is unable to hold the necessary level of accuracy.

The following images show this inaccuracy in more detail - the first image shows a 5x5x5 LUT expanded to a full 17 point LUT, compared to the real 17x17x17 LUT shown in the second image.

5x5x5 Cube 17x17x17 Cube

The difference is obvious... the 5x5x5 LUT just can't hold the required data accuracy.

Profiling vs. Calibration & LUT Generation

There is a lot of confusion regarding the 3D cube profiling vs. Calibration and 3D LUT generation.

Profiling is the measurement of the underlying display's actual capabilities and present set-up. From this profile data calibration LUTs can then be generated. This means that accurate profiling is key to the level of final calibration accuracy, and the correct profiling needs to be performed based on the needs of the display.

It also means that profiling should be performed as a totally separate function from calibration, not merged together as can be the case with other Home Theatre Pro systems. This is discussed further in the Profiling Display Gamut and Gamma section below.

Pattern Generation

Another major differences of LightSpace CMS compared to alternative calibration systems is the use, or lack of, Pattern Generators.

Pattern Generators are hardware boxes used by some calibration systems to present Calibration Images to the display being profiled. This adds hardware costs to the calibration system, and relies on the Pattern Generators being accurate. Tests of a selection of the usual Pattern Generators has shown some of them to be rather inaccurate, resulting in poor final calibration results.

Light Illusion actually works with various hardware manufactures to help enhance their product accuracy - this has included Lumagen and Entertainment Experience, as these boxes also server as LUT Boxes, so can be used for final display calibration, rather than as Pattern Generators.

Uniquely, LightSpace CMS can use the direct HDMI out from a Laptop running LightSpace CMS for direct display profiling, ensuring accurate profiling workflows. This is possible as Light Illusion understands the way graphics cards work, and can control VCGT through the use of SpaceMatch DCM.

Home Profiling

The above image shows the traditional use of an external pattern generator.

Home Profiling

And the above shows the direct profiling approach that can be used used by LightSpace CMS, in addition to the use of an external patch generator.

Not having to invest in unnecessary additional hardware obviously reduces the overall cost of calibration, and maintains far more flexibility for the profiling and calibration process.

For information on using direct HDMI from a PC for calibration patterns see the Direct HDMI for Display Profiling page.

Self Generated Calibration Discs or Generators

As LightSpace CMS self-generates the profiling patches it uses based on the users settings (Quick Profile, 17 point cube profiling, etc) these profiling patches can be exported and made into any form of external profiling disc, from DVD and Blu-Ray to Quick Time movies and more.

This is possible due to LightSpace's DIP mode - Display Independent Calibration - where the profiling patches are displayed totally independently from LightSpace, and LightSpace runs in sync with the external profiling patches.

This again means there is no additional expense required in purchasing calibration discs or generators for use with LightSpace CMS.

For the ultimate in Blu-Ray calibration discs see: Ted's LightSpace CMS Calibration Blu-Ray Disk

Profiling Display Gamut and Gamma

One of the largest differences between alternative calibration systems and LightSpace CMS is the approach to profiling. Due to the advanced colour mathematics engine within LightSpace CMS there is no need to separate out Gamma and Gamut profiling, and no need to tell the system in advance the target colour space. This is because profiling is totally separate to calibration within LightSpace CMS

Using one-pass profiling, as with LightSpace CMS, allows for extraction of the required calibration information in the required format - either as a single 3D LUT, with combined Gamma and Gamut information, or as a separate 1D LUT for Gamma and a 3D LUT for Gamut, as required by the various LUT holding systems.

Calibration systems that manage Gamma and Gamut separately, or that require the calibration system be told in advance the display's expected Gamma or Gamut (target Colour Space) before calibration use inferior colour management mathematics, with results that are limited in accuracy - for example having acceptable gamma and primary colour alignment, but with poor internal colours (RGB and even CMY may be accurate, but the in-between mixed colours - blueish pinks, yellowish green, etc, including skin tones - can easily be inaccurate).

A further problem with calibration systems that need to know the final Colour Space (Gamut and Gamma) in advance, and that lock profiling to calibration, is that if after calibration you decide that the target Gamma or Gamut should be different, due to the final image looking too dark, or the display proving impossible to calibrate to the initial chosen colour space, the full profiling/calibration will have to be performed all over again with the new target colour space set.

With LightSpace CMS this is not a requirement as profiling is totally separate from the target colour space, making it possible to generate final calibrations for any target colour space as accurately as possible for the given display.

Calibration Accuracy

The aim of any calibration is to maximise the accuracy of the display within the limits of the display's capabilities, with a focus on the central core of colours within the display's required colour space. Understanding this is very important, as many calibration systems focus on the extreme colour space colours (the primary colours) only. In the real world we see very few 'primary' colours, and focussing on them for calibration can often lead to very inaccurate final results, especially as many displays struggle with accurate primaries.

Additionally, calibrating at low-light levels can be very difficult with the more cost-effective probes available, with the probes introducing errors into the profile that do not accurately represent the display. Combine this with cheap displays that have a colour cast within their back-light, that shows in low-light conditions, but is overcome by the display as brightness is increased. Such back-light cast colours cannot be 'colour corrected' out, although the profile data will cause many colour calibration system to attempt to do so, causing inaccurate calibration results.

A further potential issue with display calibration is that if the underlying display has a colour gamut that is below that of the target gamut the calibration can only effect the area of the display gamut that is capable of matching that of the target.

Display calibration systems that major only on the primary colours cannot accurately re-map the interior gamut areas that can actually be calibrated.

It is key that any calibration system understands what can, and what can't be calibrated, and does the best it can to calibrate what can, and doesn't allow what can't be calibrated to adversely affect the final result.

A good calibration system will provide ways to overcome such display and probe problems.

Calibration LUT Generation

After profiling has been performed with LightSpace CMS the calibration LUT is then generated from the profile by matching it to the required colour space. This LUT is what then calibrates the display accurately.

Home Calibration

For home cinema users the main LUT boxes supported are the Prisma LUT box, the old eeColour, and the Lumagen Radiance range.

Calibration Verification

After the calibration LUT has been applied its accuracy can be verified by re-profiling through the active LUT. The larger the patch set used for the re-profiling the more accurate the verification will be.

Additional Technical & Support Info.

Operating System: Windows 7/8/10
PC Requirements: Minimal - 2Gig Ram Laptop, with HDMI
Mac Operation: Via a Virtual Machine or Boot Camp
User Guides: Software User Guides
LightSpace CMS Demo: Downloads
German language version of this page: displaycalibration.de

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