PixelFormat.Format8bppIndexed in Bitmap Hangs!

[Mil]

Hello,

I'm trying to convert Images using Bitmap class. I want to use
different options for example
reduce the size of image.

In my code I tried to create a Bitmap class instance with a Bitmap's
constructor:
new Bitmap(source.Width, source.Height, PixelFormat.Format8bppIndexed);

The result was that program stopped executing and started to hang. If I
create a Bitmap
with a constructor Bitmap(source.Width, source.Height) everything is
ok.

Does anyone know what happends when I give PixelFormat class as an
third parameter
to Bitmap's constructor?

So, If this does not work how should I create different type of Bitmaps
with different features?

My purpose is to convert Color Tiff image to as light GrayScale Tiff
image as possible (ligth = size of the file is smallest). Can C#'s
Image handling classes help me or not.. anyone know
about this?

Cheers.