Instructions
M Mode:
In this mode,you can adjust flash brightness according to your own preference,the speedlight will flash under the camera synchronous signal.
S1 Mode:
In this mode,DF-400 will trigger flash with the main speedlight first flash,the effect is the same as using radio trigger.When using this mode,your main speedlight should be set to manual flash mode,using neither TTL flash system nor red-eye removal function which caused multiple flash.
S2 Mode:
S2 mode is similar to S1 mode and is also known as “preflashing cancel mode”,but it can ignore the preflashing from TTL,so you can use it to support the main speedlight that working in TTL mode.In particular,if S1 mode is unable to synchronously flash with your built-in speedlight,you can try to use S2 mode
Okay straight manual flash very basic. Is this what you have. Are you saying that the flip flash of the D80 goes up when you have the DF400 mounted on the hot shoe. You may have to look in the manual of D80 to turn off the on board flash. You may be able to use the D80 onboard flash in manual power mode. (some one will chime in if I am wrong.) You can use that to also fire the the DF400 in S1 mode. You may have to test the power modes of the D80 to be low as not to affect the light to subject from your camera but the DF400 will light the subject.
Basic math Guide Number(33 at ISO 100) = [Flash to Subject Distance] x [F-Stop] so lets say you want shoot at an aperture F/4 you could use 33/4 = 8.25 feet
Hope this helps.
Lou Cioccio