It should operate in its Auto or Manual mode on any camera.
But TTL likely is an issue in many cases. For sure, it cannot do the new digital iTTL with the D40. If TTL with the D40 is an issue, then you need a new model flash from current production (SB-800, SB-600, etc). If not concerned with TTL, then it should work in its Auto or Manual modes.
Do you have the SB16 'A' or 'B' version? the difference being the hotshoe, with the 'A' being a standard version and the 'B' designed specifically for the F3.
Regarding the flash, it has 3 modes, M, A, and TTL - so compatability is a relative feature. If you do in fact have the 'A' version, it will work in at least Manual and Auto modes, I don't own a D40 so don't know if that camera supports conventional TTL.
M and A modes are trickier to learn, but the SB16 has flash scales on the back anyway so calculations are quick.
edited to add: on your film bodies, again, if its the correct version, it will be fully compatible with the F601 only M and A modes for the FM2n.
Hi, and thanks for the info so far, I'm not sure as to the exact model, but it has the standard fitting for the top of all my slr's and does actually "go off" when fitted to them, but I have never used it with film in the camera's and not so far used it with the D40.
I guess I should load each slr with a film and experiment, but it would be usefull to be almost sure of the correct settings, just so I don't waste time, film and money on developing ruined film.
If I use it on the D40, would this give me an indication of it's results with the film slr's, or would the results be totally different?
I also have a couple of SB16's and now own a D40. I tried it on the D40 and found it will work in either the manual or the two auto modes, but does not work in TTL mode. You can use it but will need to experiment with exposure. It works best in the manual mode of the camera where you can choose the f stop and shutter speed. Rather than guess at settings I bought a new SB600 to use on the camera. I am saving the SB16's for use with my film cameras and as an off camera slave.
I have in fact used the SB16 off camera as a slave, triggered by the built in flash of the D40. I attached a simple photosensitive trigger to the SB16 to trigger the flash. It seems to work quite well for me at least. It is said that the D40 triggers a preflash to set the TTL correctly. I use the camera on manual and apparently the preflash is not present. Otherwise it will trigger the remote flash too soon.