[NTG-context] Scaling down the resolution of used pictures

At the moment it is not very important, but my other question remembered me about an old situation. I do not use graphics a lot in my ConTeXt files. But some time ago I used several pictures with a very high resolution. This made the resulting PDF very big. I did not expect the PDF printed on a printer with a higher resolution as 1200 DPI. Is there a way to have the included graphics not be bigger as necessary (without changing the original pictures)? Again, at the moment it is not urgent. But when I come in the same situation again, it would be nice if the resulting PDF was not five times as big as necessary. And maybe the answer is useful for someone else also. ;-} -- Cecil Westerhof