huh? i don get u man...  the pop up flash will still fire a flash to ur subject. Making ur subject now with 2 lighting source (ur Wireless flash and ur pop up flash)....many ways can be done to overcome the flash from ur pop up flash eg like achew said..use 1/200 or higher/cover with exposed film or tissue.

kev da man : OOF?

U still don understand wht im trying to say...from ur picture..yes i can see tht u r using wireless flash...and i can see 2 light sources...1 from your pop up flash...1 from ur f42.... Go try this...shoot something tht only has 1 source of light which is from ur f42, without covering ur pop up flash. If u can do it...let me know how..i really want to know..

is some situation u need the pop up flash to fill-in some shadows. But im trying to say here, with juz only light source from ur f42...the wireless flash effect is much greater and add 'mood' to ur picture..and also u can bring up some details from ur subject surface if ur flash angle is right..this method is called shadow relief... and back to the original post..i said nikon CLS is able to disable the pop up flash totally... and now u tell me tht even if the pop up flash fires...that would create classic direct flash shadows no doubt yes its nice!!! but not always..

here..try do this..

kev da man: The onboard flash does interrupt IF you are shooting at the flash sync speed or slower, high ISO, bright apertures and much closer distances. However, in my wireless flash shots, I did not face the problem of onboard flash getting in the shot much at all, most likely due to shooting at further distances.

AlphaBeta: The easiest way to remove the influence of the pop-up flash in Sony wireless is to have some distance. For 'classic' portraiture with a few meters from the subject and lights further away, the pop-up is simply negligible. With the A900 and F20 at ISO400 F5.6 1/200s, and a subject 2 meters away, there is no influence of the F20 on the picture.

So here's an experiment for your D90; turn off the lights and shoot without flash at 1/200s F1.8 ISO1600. Then set your pop-up to WL commander and "--", raise the pop-up (but do not add the SB-900 to the equation) and see if the pop-up contributes any light.

Dynamic Range Optimizer. You have it in your A200 also but only up to Advanced. Level 5 is only on the A700-A900.

kev da man: Whatchu talkin' about Willis? Advanced is supposed to underexpose to prevent highlights from blowing out. So you should see less highlight clipping!