Eyron wrote:

> If I have a set shuuter speed (ie sync at 1/125 sec)

> and the correct
> aperature reads say  F9 .

So the camera is in shutter priority mode, or is it in program mode?

>
> But I need a lower F stop to limit depth of field.
> Will minus 3 stops of exposure control alow this and give me a 3 stop larger
> aperature?

First of all, -3 means 3 stops less exposure. In shutter priority mode,
this would close the aperture further, which is exactly the opposite
of what you want. So you neeed to to get to f3.5 or so to have much less
depth of field. Going with a +3 setting will give you less depth of field,
but your image will be 3 stops overexposed. What you really want to do
is set the camera in aperture priority mode, then pick around f2.8 or
f3.5 if you want shallow depth of field. The camera will then choose the
appropriate shutter speed, which in this case would be 1/1000th of
a second. If you have an  slr,  flash usually wouldn't work properly
at such a high shutter speed(since at high shutter speeds, the
shutter curtain is never fully open over the whole film frame or sensor)
In that case, you would want to lower the ISO rating the camera is set
at if there is room to do that. So if you lower the ISO rating by three
stops(ie from 400 ISO to 50 ISO), you can get roughly f3.5  at 1/125th
of a second exposure.

>
> Also what would my F stop be here?
> Are there any drawback to use exposure compensation. ( ie noise etc.).
>
> EEO