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Phocus 2.9 Colour Calibration

Closed Loop Colour Calibration

We now support custom colour calibrations directly within Phocus without any need for the usage of 3rd party calibration software. While the standard factory colour calibration for our cameras will generally work very well there are situations where you will want to use a custom colour calibration made using the exact lightning setup used for the shoot.  Calibrations made using the new closed loop colour calibration will be used directly on the raw camera data as a direct replacement of our factory calibration, thereby providing the best possible quality.


How to use it

In the Reproduction tool a new Colour Calibration popup menu has been added. By default this will say Factory, which corresponds to the same default colour handling used by previous releases of Phocus. In this menu you can select the Edit… option in order to bring up the Colour Calibrations dialog. Note that this dialog can also be opened via the Window menu where it has the keyboard short cut alt-cmd-C.

 

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In order to add a new calibration make sure that a suitable image containing a colour reference chart is shown in the viewer before opening the Colour Calibrations dialog.

If you have no existing custom calibrations the dialog will move directly on to the calibration interface. Otherwise use the + button on the left (keyboard short cut is +). In the calibration interface you will see the selected image together with an overlay reflecting the type of colour target selected.

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The standard workflow from here will be to:

1) Select target type

Out of the box we currently support ColourChecker, ColourChecker SG and ColourChecker DC targets. You can also use the + button to add your own target references. (see image above).

2) Align target location

While you can make a manual adjustment of the overlay indicating target position, normally you will just have to press the Auto Locate button and your target will be automatically located.

3) Calibrate

Press Calibrate to perform the actual calibration. If this is successful you will get basic ∆E statistics. Using the Mark ∆E > slider you will get feedback in the image showing patches that deviate by more than the selected ∆E value.

4) Create the calibration

Once you’re happy with the calibration result the actual calibration is stored by clicking the Create button and you will return to the base interface of the Colour Calibrations dialog showing you the list of existing calibrations. Here you will also be able to enter a text description of each calibration.

5) Using the calibration

To use the new custom colour calibration, select it in the Colour calibration pop up menu in the reproduction tool. The calibration itself will be embedded in the 3F file along with the other adjustment settings so there is no need to move the stored calibrations between host computers. If you view an image containing a colour calibration that is not already stored locally it will be automatically copied to the computer.

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 Variable Correction for Scene Calibration Tool

In the Scene Calibration tool a new slider allows you to make fine adjustments to the intensity correction.

1) Start by creating an exposure of plain white non-reflective material in the same illumination as your main subject. This should show any light fall off and colour shifts that are affecting the image. Capture you main image as usual (it will show the same colour and illumination issues as the white frame).

2) Import both images into Phocus.

3) Select the white frame and using the scene calibration tool click the create option. You will be prompted for a name.

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4) Now select the actual image to be corrected.

5) From the drop down selection arrow of the scene calibration tool select the calibration file you have just created. Ensure the tool is switched on (small tick box in top right hand corner of tool box).

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6) Now tick the remove cast box and the “equalise intensity” box if required.

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7) If the correction is too harsh drag the intensity slider to the left until the correction is at the desired amount.

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