Thanks graham I also thought that the f-stop will be included but when I did the calculations it came no where near what I got so I added the 1.4
I was wondering if the speed could have hade a difference to what the camera specs are. graham lets say the camera setting for flash is 200 and I want to shoot at 500 will I have to divide by 4 as it is 4 settings higher than the camera's speed for flash