Originally posted by jayman_1975 I just did some more testing and have noticed that while in TAV mode, the auto ISO value doesn't change when I flip the flash up. It will use the same values for flash on and flash off. Strange. But in AV mode, when I flip the flash up, I can instantly see the ISO value drop to account for the extra lighting from the flash. I'll have to research this more.
That is the general difference in using manual setting vs auto settings with flash. In manual mode the camera let you control all settings and only add fill in flash when flash is used. I guess Pentax use the same logic for both manual mode and TAv mode (even though the ISO is auto in TAv).
So you need to use exposure compensation in TAv to adjust ISO (and the mixture between between ambient and flash light). Or switch to manual mode and set ISO manually to get full control over the flash.