[logback-user] How to suppress image logging in logback-access?

I'm using logback-access with Jetty. It's working fine, except that http requests for images (*.jpg, *.gif) are getting logged. Most app servers suppress these log records because they bloat the logs. When I was using the old Jetty NCSARequestLog object, there was a setIgnorePaths() method that worked, but the logback RequestLogImpl doesn't have a similar method. I'm pretty sure there's a way to do it in logback-access.xml, perhaps using some kind of filter. Does anyone have the appropriate syntax?