A new discovery - In Macro mode, the Nikon D90 commander flash mode will be deactivated and your remotely controlled Nikon SB-900 will not fire no matter how hard you ask it to. It will only work if you have it on camera.
Here, a toy is used to see what the Nikon 18-200 is capable of. Shot with remote flash placed underneath the toy (to give it a more sinister look). The diffuser is used. Distortion control corrected within Nikon D90.