Back now and I have checked the D50 manual and see the available flash modes with the SB22 are : NonTTL Auto and Manual. Non TTL auto is where the flash is measured by a sensor on the flashgun rather than in the camera. This means you have to be careful that the sensor is not receiving light direct from the second flash unit rather than light reflected by the subject.
Probably easier to control using manual. In manual you do actually have a form of power reduction by using the wide angle diffuser. The flash is quoted as being Guide No 25 and reduced to G/N 19 with the wide angle adaptor.
A link to the pictorial view and some specs of the SB22
http://www.mir.com.my/rb/photography...SB22/index.htm
Don