Canon 1Ds compared to Canon 1ds Mark II
Here is a comparison of the Canon 1Ds 12 megapixel and the Canon 1Ds Mark II 16,5 megapixel, to show you how much visible difference there is between these two camera's.

The middle of the picture is enlarged on 100%. Foto is made made Jack Flesher.

Although there is a difference of 5 Mpixel or almost 40% more pixels between the camera's there is little difference to be seen. 12 megapixel camera's already deliver a lot of detail. Visible differences can be seen when there are at least 2 or 3 times more pixels. So with a 24 of 36 megapixel camera you will see some difference. But even then it will be depending on the target, there must be a lot of detail to be seen otherwise the more megapixels will be useless.

The photo of the 1Ds has been upsized to match the 1Ds Mark II
Photo by Jack Flesher
Detail of the Canon 1Ds. Move your mouse over it to see the 1Ds Mark II overlay.