How The Hell Did The Zapper Gun Work?

[punkonjunk1024]

OK guys, I just thought of this...
The powerglove required all that crazy stupid hookups to work, but the damn zapper gun required nothing, and it was super accurate! ON A FREAKING 8BIT OLDSCHOOL SYSTEM!

I've always kinda taken this miracle for granted... can someone explain it?

[Beldaran]

From Wikipedia:

Technical overview

When the trigger was pulled, the game blanked out the screen with a black background for one frame, then, for one additional frame, drew a solid white rectangle around the sprite the user was supposed to be shooting at. The photodiode at the back of the Zapper would detect these changes in intensity and send a signal to the NES to indicate whether it was over a lit pixel or not. A drop followed by a spike in intensity signaled a hit. Multiple sprites were supported by flashing a solid white rectangle around each potential sprite, one per frame.

It is possible to cheat in games by changing the brightness and contrast of the television, or pointing the gun at a bright light. The gun thinks it is pointing at a solid white target and will report a hit. If there are multiple targets, the "hit" target will be the first to be lit with the white square. This is not as consistent with a fluorescent lamp due to the possible differences in timing of the lamp's flicker verses the timing of the television's refresh rate.

This cheat, especially when done by pointing at an incandescent light bulb, seems to go against the drop – spike requirement, but it works. Changing the brightness and contrast so this cheat works can greatly decrease the life of older model television sets and cause the picture to look bright and washed out, which is why pointing at a light bulb is recommended. Pointing at a bare bulb seems to work better than covered, and cheap incandescent bulbs seem to work better than higher quality bulbs.

Additionally, by using a magnifying glass on the gun, it fools the receptor into thinking that the rectangle is much larger than it actually is, allowing for a shotgun-like effect that will cover the entire screen.

[punkonjunk1024]

That's absolutely ingenius. I couldn't figure it out. Whoever thought of that is a goddamn genius.

Thanks beld, that helped me out. I was baffled. :)

[Starkist]

Additionally, by using a magnifying glass on the gun, it fools the receptor into thinking that the rectangle is much larger than it actually is, allowing for a shotgun-like effect that will cover the entire screen.

Heh, I can see the possible third-party attachments taking advantage of this. A shotgun add-on, anyone? :)

[MANDRAG GANON]

I always thought this aswell, I always wondered why the SNES needed a little tracker thing on the tv but the NES needed nothing but the gun. Then a couple months ago I got a zapper from one of my friends and was playing and noticed the square thing.

I wonder if there ever was a 3rd party zapper, surely if there was there woulda been a shot gun or atleast a rifle. *shrugs*

Edit: Haven't found any 3rd party zappers but I found a modified zapper to be a sniper rifle http://www.g4tv.com/attackoftheshow/features/52389/Project_Duck_Hunt_Sniper_Rifle_.html

[Cloral]

I guess that's why they also called it the 'light gun'.

[Tygore]

I guess that's why they also called it the 'light gun'.

I can't believe I've known about this mechanic for some time yet never made that connection. I guess that also makes the term "Light Gun" somewhat obsolete, since modern shooters use some kind of tracker and can show you exactly where on the screen you shot.