I have posted numerous threads with settings for the Inon strobes and Canon cameras that should appear under searches.
There are multiple issues to deal with. If you are not able to effect power sufficiently using the strobe sTTL exposure knob then you can go into the Func Set button on your camera and set exposure, Flash +/-, set it down 1 full stop and try that. If needed set it the 2 full stops under. Yes, you can use both the camera flash compensation control and the strobe compensation control in P/A/Av/Tv camera modes with the strobe in sTTL mode with the camera flash set to Auto under menu.
Frankly, I prefer the EA mode, set camera f stop to match strobe f stop on power knob, if you wish to under or over expose set either the camera f stop or strobe f stop power knob to a different f stop without changing the other.
Example, set camera to f8 and set strobe to f.5.6. That should result in one stop under on the strobe exposure. Shutter speed example, 1/60 to 1/125 is a full stop change in exposure, etc.
You need to learn your shutter and f stop scale exposure equivalency:
F-number - Wikipedia, the free encyclopedia.
BTW, setting your S90 or G11 camera strobe to Manual under Menu button allows you to shoot EA or Manual with your Inon strobe in Av/Tv/Manual or select P/A on your camera mode dial and then select sTTL on your Inon D2000/Z240 and shoot sTTL. This works because Auto or P (program) on your S90 or G series camera and most Canon cameras overrides the "manual" flash setting under the Menu button. The setting is sticky and when you return to Av/Tv/Manual your camera strobe will be back to Manual and of course with the camera set to Manual exposure mode the camera strobe is always Manual (and no preflash of course as is always the case when Manual camera strobe is selected0)
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