I plot files with color raster attachments. When I plot to PDF with the raster settings left as color, the plot comes out smaller than if we modify the setting and plot the raster greyscale. Why would greyscale image plot out larger than a color image?
The difference in file size is being caused by the 'RGB Raster compression' method being used inside of your plotter driver file. If using JPEG compression, RGB raster compresses very well, better than index-color or binary raster. If using ZIP compression, index-color and binary raster compresses better than RGB.