The micaToolbox uses 32-bits/channel for all image processing. These images will generally be linear (unless you’ve selected non-linear when loading the image), and as a result will often be very dark in appearance (dark areas of the image are almost impossible to see).
ImageJ displays 32-bit images by specifying the minimum and maximum displayed value, which for calibrated images defaults between 0 and 100% reflectance, and for cone-catch images defaults between 0 and 1.
You can manually alter the display brightness using the “Set Min and Max” tool provided with the toolbox:
plugins > micaToolbox > Image Visualisation > Set Min and Max
If the image is too dark, reduce the upper value (e.g. try max=50 for calibrated images, or max=0.5 for cone-catch images).
Note that changing the min and max display values does not affect image pixel values at all – measurements are unaffected – and this is a useful tool for seeing darker information in an image.
See also making presentation images.