How can I get correct portrait flash exposures?

[MiqsPix]

I have a Nissin Di622 speedlight flash on my Canon 1000d but cannot get consistent inside house portrait flash results. Some are overexposed, some are under. I know if I use the auto setting all will probably be ok but I am trying to learn by using either aperture priority, shutter priority or manual set up, whichever is the best. I have selected all the respective settings on the camera e.g. portrait, external flash, and tried flash exposure compensation but still cannot get consistently what I want. Some are great, some are awful! Unfortunately I haven't got any LCD screen or distance readings on the back of my speedlight so I can't work it out as suggested. Is there any way I can be more successful with flash using the Nissin Di622?

Edit:
I now realise I wasn't using the E-TTL II Evaluative flash mode setting. I now have more consistent results. Unfortunately I want to use ISO 200 to reduce noise and keep quality and when I set this I get the aperture setting flashes in my viewfinder. Something is obviously wrong! I want to use an exposure with flash of 60-125th sec with an ISO of 200, as my younger subjects move. Can this be done?

[ianpinion]

Hi MigsPIX,

Does your flashgun have a high speed setting (HSS)? I think what you're finding is that the camera is slowing the shutter speed down because it thinks that at ISO 200 it will underexpose the image. If you put it in HSS mode it will work with the shutter speed you manually select.

Personally, I find it easier to use the flash in the P (Program) setting and if the camera is slowing down the shutter speed I dial in some positive exposure compensation, take a test shot, view the result and adjust as necessary until I get it how I want whilst using the HSS mode.

[greenwing]

Forget shutter priority or program for indoor flash shots. The camera will just open up the lens wide in the low ambient light, and that may not be what you want.

Use aperture priority and the camera should detect the flash & set flash sync speed, probably 1/60? If you want a faster shutter use manual & set it as you wish up to 1/200 or whatever your fastest sync speed is.You should probably ignore the camera's meter, it shows the ambient light and doesn't know what the effect of flash will be. Let eTTL do its thing.

Chris