Im not really sure that im following your train of thought on this.

If a camera takes a picture that is 8mb in size, whether there is 'noise' on the image or not, its still only going to be 8mb in size isnt it?

As i said, not sure if thats what you mean but right now im not understanding how an image that has 'noise' on it differs than an image that is noise free if the end result is a filesize thats 8mb.

Regards,

Lee