A fellow Sony A100 DSLR user, Tom Harvey, has done some extremely thorough testing that illustrates the flash exposure problem.
This is with the camera's own popup flash.

Tom reports:
I cannot get anything other than TTL/ADI to change anything that I would not expect to change on my camera.
Here are my test shots, all set to AUTO (on the mode dial) with single setting adjustments indicated...




- [Ambient light, ADI, TTL ]
As per previous findings TTL about right, ADI underexposed.




Using ADI
- Ambient only [no adjustment, -1Ev, -2Ev] - Ambient & Flash [no adjustment, -1Ev, -2Ev, +1Ev]

Editor's comment:
Note how negative exposure compensation makes image brighter when Ambient only , this is the opposite to the result with Ambient & Flash

We are referring to the setting in Custom Menu 1 - see below:





Using TTL
- Ambient only [no adjustment, -1Ev, -2Ev] - Ambient & Flash [no adjustment, -1Ev, -2Ev]
Editor's comment:
Again note the opposite effect when Ambient Only is selected in Custom Menu 1




Using ADI
- [Wide AF area, Spot, Select (centre)]
No significant changes.





Using ADI
- [Matrix metered, Centre weighted, Spot]
No significant changes.





Using ADI
[Night portrait, Night Scene, Sports, Macro, Landscape, Portrait ]
Nothing unexpected





Using TTL
[Night portrait, Night Scene, Sports, Macro, Landscape, Portrait]
Nothing unexpected





Using ADI, Manual focus
- [On subject, minimum, maximum]
Distance information obviously is taken into account, but infinity focus seems to give roughly the correct exposure.




Using TTL, Manual focus
- [On subject, minimum, maximum]
No major impact.





Using ADI
- [DRO off, DRO standard, DRO+ ]
No major changes. DRO+ helps a little.

--
Tom

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Now how can we get Sony to look at this ADI problem?

David