I have been trying to learn more about the flash capabilities of my Nikon N90. Reading the manual, it seems that with many Nikon branded TTL flash units, the camera automatically selects "automatic balanced fill flash" over "standard TTL flash". The former apparently takes account of ambient light and results in better exposure of the main subject; the latter can tend to over-expose the main subject and under-expose the background. My favoritest flash of all time is not a Nikon branded one, but my Sunpak 555. I recently acquired a Sunpak Nikon TTL module and cable for it. Does anyone have any idea how the N90 will work with the Sunpak on TTL mode? Any idea where I could find some substantive commentary on the Nikon TTL capability of the Sunpak 555?