For clarification: With digital cameras there is a longer shutter delay and therefore a different sync cue; that is taken care in the DX speedlight models and they will operate flawlessly on the film cameras as well. The non-DX speedlights may not properly function with a digital camera. Both the SB-28DX and SB-28 will work on a SU-4, the question is how not to pre-trigger them with the pre-flashes when in 3D Multi-sensored-Matrix-balanced fill flash. The way to do it is simply to set the triggering flash in standard TTL, (one icon only, showing) or tilt the head of the triggering flash. That is all. If someone wants a flash for a film camera, that will serve him later on a digital camera such as the soon to come D100, then it is better to get a DX speedlight, either the SB-28DX or the SB-80DX.