Why are there THREE layers when I load ONE bmp file ?

Hi,
I have a simple question.
It may not related to the Igor Pro.
When I load a single bmp file (ex. SEM image or CCD image), there are 3 layers in one bmp wave.

I used the command •ImageLoad/T=bmp (actually 'Load Image...' used from Data tab)

To preview the image in 2D in data browser, I change the number of layers 3 to 0.
I wonder if it is normal or not.

Thanks in advance.
The image is composite Red, Green, Blue (RGB) colors even if it is a grayscale image.

To convert to a single layer grayscale use imagetransform.

imagetransform /O RGB2gray imagename // note this overwrites the image with the grayscale (single layer) image. If you don't want to do that omit the /O flag.

Andy