I have the SB-28 and it works fine on the D3200.

However the D3200 will have to be in M mode so you can set the shutter sync speed. I use 1/125. You will need to set the aperture in A mode and then go back to M to take your flash photo.

The SB-28 will need to be in A mode. When you first turn the flash on the ISO display on the flash LCD will blink. Use the + or - button to set your ISO. It can only be set immediately after turning on the flash and while the ISO is blinking.

Now you can use the zoom button to set the lens focal length and the SEL button to set the lens aperture to match what you set the D3200 aperture to.

After you set the ISO, lens FL and aperture you will see a line of black squares directly above the distance scale in feet. The f stop you chose will be fine as long as your distance from camera to subject falls under the black squares. If they fall outside of your distance simply change the f stop on the flash and then the D3200 until they do.

You should get a perfectly exposed photo automatically as long as your f stop and ISO is set correctly and the distance falls anywhere under the black squares.

As a starting point and with a 50mm lens, ISO 400 and f5.6 set on both the D3200 and the SB-28, you should get good flash photos Automatically at any distance between 5 and 40 feet.

I don't have the SB-20 so I can't help you there. But the SB-28 is the newer flash and should be preferred.

edit: If you don't have the manual for the SB-28 you can down load it from the NikonUSA site.

Good Luck,
Len

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