Gradient Brightness Correction is necessary when you notice the image dataset slowly brightening or darkening as you slide through it in one direction

First, choose the Direction in which the gradient occurs: X, Y, or Z.

There are two Correction Methods available: Multiplicative and Additive. Which method should be used depends on the processing applied by the image acquisition device. Scanned image data typically indicates whether the device uses linear or logarithmic processing. If the processing is linear, use the Multiplicative correction method. If the processing is logarithmic, use the Additive correction method.

With Enabled ROI the gray value range within which the correction is applied can be restricted. The minimum and maximum gray values of that range are selected in the Histogram ROI.

Click Apply to correct the Gradient Brightness based on the given settings.

The following example illustrates a brightness gradient from the exterior to the interior along the Z-axis. This gradient can also be seen in the Slice Mean gray value, as shown in the Histogram section and the following diagrams for the X-axis. Gradient Brightness Correction is applied to Direction X without Enabled ROI. This correction significantly improves the gray-value image. Consequently, the gray value histogram shows a significant improvement in differentiation between pore space and solid phases. The slice mean gray values now have a linear trend along the X-axis.