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# Camera/Scanner Profile Parameters Dialog Help Window

LProf is an open source application that creates ICC profile for cameras, scanners and monitors.

#### Resolution (CLUT points)

This set of radio buttons are used to select how many points will be included in the profiles Color Look Up Table (CLUT). Select smaller values to make small but less accurate profiles. Select larger values to create larger more accurate profiles. This can also be used to make Matrix/Shaper profiles by selecting the Matrix radio button. Matrix/Shaper profiles will be the smallest of all profile types.

#### Profile Verbosity

These radio button allow you to control how much additional information is stored in the profile. Selecting "Only required tags" will store only information that is absolutely needed in the profile. This makes for smaller profiles. "Store additional tags" stores additional information but does not store measurement information. "Verbose, store anything" will include everything that can be included in the profile including measurement information that is useful to the Profile Checker and other software such as iccexamin.

### Regression Parameters

This section now features an automatic smoothness feature. With "Auto optimize smoothness" selected the profile generation code will use Randomized General Cross Validation (RGCV) to try different smoothing factors, and to determine (and eventually use) the "best" one, with the lowest RGCV estimate. Best in this case means the smoothness factor results in the lowest delta E. This is based on:
Wahba, G., Johnson, D. R., Gao, F. and Gong, J. "Adaptive tuning of numerical weather prediction models: Part I: randomized GCV and related methods in three and four dimensional data assimilation." TR 920, April 1994.
A short version is located here:
Monthly Weather Review, 123 (1995), 3358-3369, under the title "Adaptive Tuning of Numerical Weather Prediction Models: Randomized GCV in Three-and Four-Dimensional Data Assimilation."
Automatic smoothness optimization can be influenced by setting different values in the spin box to the left of the Auto optimize smoothness radio button. Setting positive values in the spin box will result in smoother CLUT curves than the automatically estimated smoothness value and setting this to negative values will result in CLUT curves that fit the data points more closely at the expense of reduced CLUT curve smoothness. In most cases the default value of zero (0) should yield optimal results and is a good starting point. In some cases users have reported that the smoothness factor that yields the lowest delta E does not give the best actual results. Usually this shows up a color reversals in very dark and/or highly saturated parts of images. This has been specifically observed when profiling Nikon film scanners with very highly saturated/dark greens. The solution is to increase value in the "Auto optimize smoothness" spin box or to set a "Manual smoothness" value that is higher than the automatically selected value. There are 13 smoothness factor values that can be selected by either the "Auto optimize smoothness" feature or manually.
Users can also set the smoothing factor manually by selecting the Manual smoothness radio button. This has the advantage of running faster during profile creation but users will be on their own for selecting the best smoothness setting. Values between -6 and 6 are valid with higher values resulting in increased smoothness. Values near zero (0) are a good starting place.

#### White Point Handling

Starting with version 1.11.5 LProf now features a new set of controls for setting the profiler white point handling. These features are very powerful and should allow users to select the correct white point handling for each device. The white point location can be set in six different ways using the radio buttons in the "Location" button group. For most uses the "Dmin target patch" and "Adapt device white point" are the right choices. "Adapt device white point" is how LProf has done this in the past. On the right side of the Location button group are the RGB, L*a*b* and XYZ buttons. Selecting these will allow you to specify a specific white point. The XYZ and L*a*b* buttons will allow you to specify the white point as an absolute value in either the CIE-Lab or CIE-XYZ color spaces. The RGB setting will set the white point to a user specified RGB color in the target image. You can also use the "Pick from image" button to select an area in the target image that will be used for setting the white point. The radio buttons in the "Luminance Scaling" button group are for setting how the profile will handle RGB values in images that are higher than the RGB values for the calculated white point.

#### Chromatic adaption & viewing condition

This functionality has been completely revamped with the release of LProf version 1.11.5 and is now much more powerful. It is now possible to set both the "Assumed viewing conditions for the captured medium" and the "Assumed PCS viewing conditions".

The "Assumed viewing conditions for the captured medium" are the lighting that were in use at the time the profiling target was captured. For most situations this should be set the the default value of "Original scene - Bright Outdoors". There are other pre-defined setting that are based on published standards that can be selected. In addition, users can set these to almost any arbitrary set of values. Settings other than "Original scene - Bright Outdoors" are in general very specialized and should only be used by users who know specifically why they are making this change.

In most cases the "Assumed PCS viewing conditions" should be set to "ISO-364 P2 ICC reference medium". Like "Assumed viewing conditions for the captured medium" setting there are a number of industry standard presets available and users can select almost any set of arbitrary values. Settings other than "ISO-364 P2 ICC reference medium" are in general very specialized and should only be used by users who know specifically why they are making this change.

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