Fred, at 6 meters (~236"), your only real option is likely a PDF versus...what format would you use? And to go that large with a PDF, one has to use a PostScript file and then Acrobat Distiller using a certain preset in order to obtain a usable PDF. I have done roughly 10 meters in length to PDF. All image types have a pixel limitation (number of pixels in the image).

I often have full background images. These need divided and reassembled in XDP as XDP cannot handle a single image that large when using PDF. Because of the viewing distance that banner was to be seen, I made the bitmap elements to be about 70 dpi. It was also full of large type and vector elements.

Mike