...in what Scott Tucker is working on- a pure white HDR... I would also suggest trying a "dummy" HDR file that is really an LDR... maybe it just needs the "hdr" extension but without the actual HDR data...(I think this would be possible in Photoshop).

...here's a test render I made in Vue 5 when it first came out two years ago- the TOTAL illumination for this scene was a SINGLE white tile (240 x 240)... and yes, if you use a gray-scale ramp- you can create a DIRECTIONAL light source as well...

Being LDR- the render is quite FAST.  Needless to day, LDR doesn't have the Dynamic Range of HDR- but it (LDR) is a really FAST and a SIMPLE way to light a scene...