Recently, I feel that I need to get a flash light for my Fm3A. Since I also have a S3 Pro, I was thinking if I should get a SB 800 or 600. Until today, I strongly feel that it would looking pretty strange to have a Fm3A with SB 800 mounted on top of it. I am wondering, if there are other choices that would match with the look of the fm3a?
sb 15, i used to use one on my FE2, worked brillantly (looked great). i think there only available 2nd hand now. i know the S2 used standary TTL, don't know about the S3, think it's i-TTL so a SB 50-DX.
Any of Nikon's TTL capable speedlights will work with your camera. The SB15 was the first hotshoe mounted flash that featured TTL (early 80s). The SB27 may be still available as new old stock so check around.
The SB15 has tilting flash tube and the SB27 has a pull-out bounce card. Both units have the ability to point downward for close-ups. The SB30 is TTL and still available and can also point downward.
Even non-TTL auto flash units will work as well as the manual ones. The short story is practically all Nikon Speedlights ever made will work in one mode or another on your camera. Keep in mind their power output or GN varies widely among models.
I recommend you buy the most powerful one. Currently that's the SB800 but that doesn't fit your criteria of what looks best on your FM3a. So from the site I referred to earlier take a look at them all and see which one you like and see if you can find one on ebay or your local camera store.
As for usefulness keep in mind a flash that can properly expose your subject 60 feet away will obviously be more useful than on that can only illuminate up to 30 feet away. For any given speedlight it's maximum shooting distance will depend on the ISO of the film you are using, the maximum or working aperture of the lens used, and if it has the option; the speedlights zoom head position. What is useful for you may not be useful for me so I can't make any recommendations.
There's some information here, here , or here that may be helpful to you.
