Image Sequence Probe

The Image Sequence Probe capability within ColourSpace enables any patch image sequence to be used to generate a profile.

The Image Sequence Probe is very unique, and has many applications, from Virtual Set calibration, to film profile generation via telecine or film scanner transfers.

The Image Sequence Probe effectively enables cameras, scanners, telecines, and more, to be used as virtual probes.

  • ColourSpace INF/XPT/PRO


ColourSpace Integration

The Image Sequence Probe is extremely powerful, and opens up a huge range of possibilities for profile generation from any process that can generate image sequences of colour patches.

Image Sequence Probe
Image Sequence Probe

The concept behind the Image Sequence Probe is exceptionally simple, and at the same time extremely powerful. Any image patch sequence can be used with the Image Sequence Probe, as all images have an expected target colour space.

This means any signal path can be used to generate patch image sequences, from a camera recording patches from any display device, to images generated via telecine from film scans, or any graphics program directly generating patch images - basically, any workflow that generates patch images!

Image Sequence Probe Settings

The Settings options provide specific Image Sequence Probe configurations.

OETF

The OETF selector enables the original image source colour space to be set, which defines the maths used when converting the image RGB values back into profile data. Any colour spaces can be used, including User Defined.

Min Luminance (nits)

Min Luminance sets the nits value 0% black is mapped to.

Max Luminance (nits)

Max Luminance sets the nits value 1000% white is mapped to.

Sequence

The Sequence ... button enables navigation to the folder containing the image sequence patches, with the editable name window allowing the sequence parameters to be defined.
The first frame in the image sequence should be selected, and the file name edited using standard printf formatting - %04d - any preceding text entered before the %, with 0 defining the padding value, and the 4 defining the width of the integer number.
Therefore, image names stuff000001.dpx, stuff000002.dpx, etc., would be defined as \stuff%06d.dpx.

Offset

Offset defines the image sequence numbering offset from zero.
In the above example, the offset would be 1, as the first image name in the sequence is one, not zero.
(Note: If the Sequence path is a single file, the Offset value is ignored.)

Step

Step defines the image sequence incremental numbering.
In the above example the images are named 000001, 000002, etc, so the step is one.

Status Window

The green Status Window shows the patch name being measured, as well as the status - Idle Ok, or Err.
The full path to the files being measured can be displayed by hovering over the Status Window.

Area

Area sets the the image area to be averaged for the virtual measurement, centred within the image.

Probe Adjustments

Probe Adjustments are generic probes settings, with consistent operation regardless of the probe in use.

Configure Matching

Probe Matching is used to match a Tristimulus to a Spectroradiometer, increasing the profile accuracy.

There are three different methods available for probe matching - ColourSpace's unique 4 Colour Volumetric Matching (FCVM), and Multi-point Volumetric Matching (MPVM), with the option to force the use of the traditional simple matrix method (FCMM).

Offset

Probe Offset enables a user to manually enter offset values for different probes/display combinations. This can be used with Image Sequence Probe too.

Extra Delay

Extra Delay sets a delay time after the image patch has changed before probe measurement starts, and manages potential delays in the image file path.
The Auto option cannot be used.


Virtual Set Calibration

There are multiple different workflows for the use of the Image Sequence Probe for Virtual Set Calibration. The following outlines the basic approach, but it should be obvious there are many different ways the Image Patch Sequence could be generated and applied within the ColourSpace Image Sequence Probe option.

While ColourSpace is fully integrated with Brompton's range of Tessera LED Video Wall Processors for accurate Closed Loop display profiling and calibration, any Virtual Set and any video processor can be accurately calibrated with ColourSpace's Image Sequence Probe.

Virtual Set

Patch Generation & Capture

As above, this is just one workflow for patch sequence generation and capture, from which users can define alternative methods.

  • Generate the required patch sequence as needed, including a matching .csv Patch Set file if the sequence is user generated
    This can be a sequence of patches exported from ColourSpace, or generated by any other method
  • Play the image sequence on the video wall to be calibrated, using a defined pre-set time per patch
    The preset patch time is just to ensure a clean patch capture
  • Record the image sequence via the normal capture camera
    It is expected the camera and video wall are pre-set to the same target colour space, which can be anything including the native colour space of the video wall
    If the camera is set to a different colour space, the recorded patch images will need to be converted back to the video wall colour space, using the Camera Tools in ColourSpace as needed
  • From the captured image sequence, extract one frame of each patch colour
    If required, average multiple images to generate a single clean image per patch
  • Save each image in a folder, with a unique frame number per patch

Image Sequence Probe Settings

Within ColourSpace, the Image Sequence Probe will virtually measure each colour patch within the patch sequence, and plot against the defined target colour space, generating a measurement profile.

  • Open a ColourSpace Profiling window, select Probe Options, and select Image Sequence Probe from the Hardware drop-down list
  • Select Connect
  • From the Image Sequence Probe Settings, set the required OETF for profile data generation
  • Set the target Min/Max Luminance
    The value can be the actual peak from the video wall, or a user defined value to normalise a measurements to
  • Use the ... button to navigate to the folder containing the patch image sequence
  • Set the Offset, Step and Area values as required

Image Sequence Probe Operation

To perform the virtual measurements, the normal Manual Measure, or Characterisation menus are used.

  • If the original patch sequence used was exported from ColourSpace, select the same patch sequence in Characterisation
  • If the patch sequence was user generated, load the matching .csv Patch Set into Characterisation, Custom Sequences, or Manual Measure, Presets, depending on the user patch sequence size
  • Start profiling as normal
  • The defined Target Gamut/EOTF within Settings will operate as normal

After virtual Profiling completes, the profile can be used as normal, either to verify the existing image chain colour accuracy, or to generate a calibration LUT, etc.


Film Scanner

Film Look LUT Generation

As with Virtual Set Calibration, there are multiple different workflows for the use of the Image Sequence Probe for Film Profile operation. The following outlines the basic approach, and again it should be obvious there are many different approaches that could be adopted.

Patch Generation & Film Recording

As above, this is just one workflow for patch sequence generation and film recording, from which users can define alternative methods.

  • Generate the required patch sequence as needed, including a matching .csv Patch Set file if the sequence is user generated
    This can be a sequence of patches exported from ColourSpace, or generated by any other method
  • Record the image sequence using a film recorder
  • Process the negative film stock
    If needed, print the negative
  • Using a telecine or film scanner transfer the film into digital images, targeting a standard colour space
  • Save each image in a folder, with a unique frame number per patch

Image Sequence Probe Settings

Within ColourSpace, the Image Sequence Probe will virtually measure each colour patch within the patch sequence, and plot against the defined target colour space, generating a measurement profile.

  • Open a ColourSpace Profiling window, select Probe Options, and select Image Sequence Probe from the Hardware drop-down list
  • Select Connect
  • From the Image Sequence Probe Settings, set the required OETF for profile data generation
  • Set the target Min/Max Luminance
  • Use the ... button to navigate to the folder containing the patch image sequence
  • Set the Offset, Step and Area values as required

Image Sequence Probe Operation

To perform the virtual measurements, the normal Manual Measure, or Characterisation menus are used.

  • If the original patch sequence used was exported from ColourSpace, select the same patch sequence in Characterisation
  • If the patch sequence was user generated, load the matching .csv Patch Set into Characterisation, Custom Sequences, or Manual Measure, Presets, depending on the user patch sequence size
  • Start profiling as normal
  • The defined Target Gamut/EOTF within Settings will operate as normal

After virtual Profiling completes, the profile can be used as normal, either to verify the existing image chain colour accuracy, or to generate a Look LUT, etc.


Camera Profiling

Using the Image Sequence Probe with a calibrated light source it is possible to profile a camera, and generate a ColourSpace profile that shows the camera's response.

A very simple approach to camera profiling is to shoot a video test chart, such as DCS Labs or Macbeth, under controlled lighting, and from the captured image generate a single coloured frame for each colour patch on the chart used.

A matched .csv Patch Set will need to be generated with the matched target colours. The colour data can be obtained from the test chat manufacturer, or via online documents such as Wiki ColorChecker, and the associated Macbeth ColorChecker Chart.

Camera Profiling

Camera Capture

Again, this is just one workflow for patch sequence generation for camera profiling, from which users can define alternative methods.

  • Shoot the chosen colour chart under controlled lighting, with the camera set to match the expected colour space of the chart - usually Rec709 for the RGB values provided by the manufacturer/Wiki page above
  • Capture a single frame
    Averaging a number of frames may be a good idea
  • Generate a matching patch sequence .csv file of the colour chart colours
  • From each colour patch within the colour chart generate a single full frame colour image
  • Save each image in a folder, with a unique frame number per patch frame

Image Sequence Probe Settings

Within ColourSpace, the Image Sequence Probe will virtually measure each colour patch within the patch sequence, and plot against the defined target colour space, generating a measurement profile.

  • Open a ColourSpace Profiling window, select Probe Options, and select Image Sequence Probe from the Hardware drop-down list
  • Select Connect
  • From the Image Sequence Probe Settings, set the required OETF for profile data generation
  • Set the target Min/Max Luminance
  • Use the ... button to navigate to the folder containing the patch image sequence
  • Set the Offset, Step and Area values as required

Image Sequence Probe Operation

To perform the virtual measurements, the normal Manual Measure, or Characterisation menus are used.

  • Load the matching .csv Patch Set into Characterisation, Custom Sequences, or Manual Measure, Presets, depending on the user patch sequence size
  • Start profiling as normal
  • The defined Target Gamut/EOTF within Settings will operate as normal

After virtual Profiling completes, the profile can be used as normal, to verify the camera colourimetry, etc.


Camera Matching

Camera Matching

The Image Sequence Probe can be used generate camera matching LUTs, via a number of different workflows.

There are a number of possible workflows that could be used, such as pointing the cameras to be matched at the same display, and capturing the same patch sequences via each camera. The basis of this approach is as per Virtual Set calibration, combined with Camera Profiling, as above.

An alternative is to shoot the same scene with both cameras, ands then extract from the captured images colours that are from the exact same locations. A singe still image, captured with the cameras to be matched, can be used.

Camera Capture

The underlying workflow is the same, regardless of the approach adopted.

  • Shoot the same patch sequence, or scene, with the cameras to be matched
  • If a patch sequence has been used, generate a single full frame colour image per patch
  • If a scene capture has been used, use a pixel sniffer to extract colours from matching locations in each camera image
    The more individual colours extracted, covering the widest possible range, the better
  • Save each image in a folder, with a unique frame number per patch frame
  • Generate a matching patch sequence .csv file of the colours extracted
    Only one .csv patch list is really needed for the master camera, although generating for both cameras provided additional flexibility

Image Sequence Probe Settings

Within ColourSpace, the Image Sequence Probe will virtually measure each colour patch within the patch sequence, and plot against the defined target colour space, generating a measurement profile.

  • Open a ColourSpace Profiling window, select Probe Options, and select Image Sequence Probe from the Hardware drop-down list
  • Select Connect
  • From the Image Sequence Probe Settings, set the required OETF for profile data generation
    The selected OETF is not really relevant for Camera Matching, as it will cancel-out when using the profiles for LUT Generation
  • Set the target Min/Max Luminance
  • Use the ... button to navigate to the folder containing the patch image sequence
  • Set the Offset, Step and Area values as required

Image Sequence Probe Operation

To perform the virtual measurements, the normal Manual Measure, or Characterisation menus are used.

  • Load the matching .csv Patch Set into Characterisation, Custom Sequences, or Manual Measure, Presets, depending on the user patch sequence size
    The same .csv patch list should be used for both camera sequences
  • Start profiling as normal

After virtual Profiling completes, the profile can be used as normal for LUT Generation, with one camera profile set as Source, and the other as Destination. The generated LIT will match one camera to the other.


Any Patch Sequence

As should be obvious from the above, any patch sequence can be used with the Image Sequence Probe, leading to a huge range of possible applications.

With the ability for any colour space to be user defined as the target against which the patch sets are referenced, the possibilities really are unrestricted.

Patch Sequence