A read only property used to indicate which one channel (if any) encodes luminance data.

A Long value.  

object.LuminanceChannel

The LuminanceChannel Property syntax has these parts:

For color Interpretations where one channel encodes a luminance value (e.g., HSL) the luminance channel is returned as a zero-based value. For mciMonochrome interpretations, for Interpretations where more than one channel is needed to determine luminance (e.g., RGB) or where luminance is not directly encoded in one channel (e.g., Indexed Color), then mcwcAllChannels (-1) is returned as the LuminanceChannel property.

For the mciPolar type, channel 0, the magnitude channel is reported as the “luminance” channel.

This property can be used to determine if luminance-based algorithms should be run on a single ChannelToProcess or if they need to be run on all channels.