How do the light guns work?

[Schenley]

In quick layman's terms, how the hell do the light guns work?

I just got two NESes which I refurbished. I got the light gun working and am playing Hogan's Alley (FUN) and Duck Hunt...

What's the technology behind those things? How could something so old work so well even on my fairly new 50" TV?

[Querjek]

Funny, I asked the same thing a while ago.

http://www.digitpress.com/forum/viewtopic.php?t=26562&highlight=light

>>Lo---

Damn, just realized I can't do that. Yet...

[Garry Silljo]

What I don't get is why all the old guns are better than the new ones? Nes, SMS, when you plug in the gun no matter where you sit or stand or go, the gun is accurate and works fine with NO callibration. New guns, you have to recalibrate them everytime you adjust your position even half an inch. My fiance loves the Saturn for all of the gun titles that are so few and far between on the next-gen systems, but always gets angry, because she'll pause and go to the bathroom, and then come back and not sit in EXACTLY the same place and suddenly the sight is off. Then she gets fed up with it and puts in Duck Hunt.... smooth sailing.

[Tom61]

What I don't get is why all the old guns are better than the new ones? Nes, SMS, when you plug in the gun no matter where you sit or stand or go, the gun is accurate and works fine with NO callibration.

How could something so old work so well even on my fairly new 50" TV?

Because the NES (and presumably the SMS) gun is stupid. All it does is look for light. Point it at a lightbulb and you'll get the high score.

[Garry Silljo]

I just tried that, and it didn't work, so you're retarded. I have a point, like it or not.

[Kejoriv]

thanks for the interesting information. I always wanted to know that.

[Arcturius]

Did anyone else ever hear the rumour about sawing the end of the NES lightgun to make it do a spread shot when they wew kids *chuckles* I always remember that from school.

[charitycasegreg]

NO. Why would you ask this question? Dont question the nes zapper. Its a question better left unanswered. Naw im just kidding. he already answered so now i cant.. :(

[8-Bit Master]

Try playing Duck Hunt by shooting at the reflection of the screen in a mirror. It works since the light simply bounces off the mirror and at the screen, and it's damn fun too. I've shot at the screen using 3 seperate mirrors, bouncing the light back at the TV.

I know, I know...............I have way too much time on my hands. LOL

[Garry Silljo]

I've done the mirror thing. It's pretty cool, but I stil say that light bulb statement was completely uncalled for. Still, Why can't the new guns work as well as the old? Never had any problems with the zapper. Have had all sorts of annoyances with every gun since.

[Querjek]

Try playing Duck Hunt by shooting at the reflection of the screen in a mirror. It works since the light simply bounces off the mirror and at the screen, and it's damn fun too. I've shot at the screen using 3 seperate mirrors, bouncing the light back at the TV.

I know, I know...............I have way too much time on my hands. LOL
I've done that with my window before. But you know what's even more fun? Doing that WITH THE LASERSCOPE!

[dr mario kart]

speaking of light guns, does anyone have any recommendations for good light guns for the ps2?

[Aswald]

The old light guns simply looked for a point of light (such as the old Unisonic and Telstar games). Shooting at any light source would do; in fact, the instructions recommended a dim room.

If you hit "PAUSE" during NES Duck Hunt, at the right instant, you'll notice that the playfield vanishes, and each duck is replaced by a block of light. Evidently this is done one at a time (in the game with 2 ducks, or clay pigeons, for that matter); it's a simple matter for the game to decide which one you "hit."

[Jaker]

OK in short ot looks at the TV and sees where you shot it at...OK someone check that because none of this make sense.

[jonjandran]

Once again :

To create this effect, the gun contains a photodiode (or a phototransistor) in the barrel. The photodiode is able to sense light coming from the screen. The gun also contains a trigger switch. The output of the photodiode and the switch are fed to the computer controlling the game.

At the same time, the computer is getting signals from the screen driver electronics. If you have read How Television Works, you know about the horizontal retrace and vertical retrace signals used to align the picture on the screen. The screen driver electronics send pulses to the computer at the start of the horizontal and vertical retrace signals, so the computer knows where on the screen the electron beam is located during each frame.

The computer normally uses one of two different techniques to figure out whether or not the gun is pointed at the target when the user pulls the trigger:

* The computer blanks the screen and then paints just the target object white. If the photodiode senses darkness after one vertical retrace signal and then light after the next, the computer assumes that the gun is pointed at the target and scores a hit.

* The computer blanks the screen and then paints the entire screen white. It takes time for the electron beam to trace the entire screen while painting it white. By comparing the signal coming from the photodiode with the horizontal and vertical retrace signals, the computer can detect where the electron beam is on the screen when the photodiode first senses its light. The computer counts the number of microseconds that pass between the time the horizontal and vertical retrace signals start and the time the photodiode first senses light. The number of microseconds tells the computer exactly where on the screen the gun is pointing. If the calculated position and the position of the target match, the computer scores a hit.

[Schenley]

you'll notice that the playfield vanishes, and each duck is replaced by a block of lightI've noticed this when I miss a duck... It happens so quickly, but if you look carefully, you can see it. Kinda like subliminal advertising.

[SoulBlazer]

So how do the modern light guns work as opposed to the eariler models? It DOES seem that all the ones from the PlayStation forward are more touchy.

[Aswald]

It's interesting that in the "old-old" days, there were numerous light gun games, in particular the odd Telstar Arcade, but not really any afterwards until the NES era.

Most, if not all, programmables ever made could easily handle light gun games. It would have been interesting to see them for the ColecoVision, Atari 5200, Intellivision (2, removable controllers), and the Atari 2600. In fact, given all of the accessories for the 2600, I'm surprised such games were never made.

I don't know if this helps understand them better, but usually such guns are built so that the light can only reach the photosensitive cell if it's pointed EXACTLY at the light source when the console checks to see if this has happened. It's like looking at something through a cardboard tube.

[Aswald]

OK in short ot looks at the TV and sees where you shot it at...OK someone check that because none of this make sense.

Sort of. In that exact instant, it checks to see if the light gun is pointing at a light source (I'm referring to the older guns). If it's pointing right at a light source at that instant, then light hits the photocell. A tiny current is created, and this signals the console that yes, the gun is pointing at the light source.

With the Duck Hunt games, if there are two objects, then only one at a time is on the screen when the game "checks". The console knows which one was lit at the time, so if the gun is pointing at something, it'll know which one.

[Schenley]

I have an old light gun for my COCO3. It was made by a third party company, and I believe there were only 3-5 games that supported it. I have two of them, and the gun still works! Unfortunately, the games are on 5" floppies (remember those?) and only one of them works.