Can An 8-Bit Light Gun Work On A Modern TV?

It’s an accepted part of retro gaming lore, that 8-bit consoles perform best when used with an original CRT TV. One of the reason for this is usually cited as being because the frame buffer and scaler circuit necessary for driving an LCD panel induces a delay not present on the original, and in particular this makes playing games which relied on a light gun impossible to play. It’s a subject [Nicole Branagan] takes a look at, and asks whether there are any ways to use a classic light gun with a modern TV.

Along the way we’re treated to an in-depth look at the tech behind light gun games, how the gun contained a photodiode which on the NES was triggered by the brief showing of a frame with a white square where the target would sit, and on the Sega consoles by a white screen with an on-board timer counting the screen position at which the gun was aimed.

The conclusion is that the delay means you won’t be playing Duck Hunt or Hogan’s Alley on your 4K TV, but interestingly, all is not lost. There are modified versions of the games that take account of the delay, or an interesting lightgun emulator using a WiiMote. We’d be happy at playing either way, just as long as we can take pot-shots at the annoying Duck Hunt dog.

Light gun image: Evan-Amos, Public domain.

55 thoughts on “Can An 8-Bit Light Gun Work On A Modern TV?

  1. My crazy idea:
    Use an IR laser diode, a polygonal mirror (for horizontal), and a mirror galvanometer (vertical) to make a “flying dot” projector, resulting in an NTSC/PAL compatible “raster scan” that only the gun can see. Overlay it on the TV screen and synchronize it to the console’s original video signal (before all the upscaling, etc. on the modern display). Bam! Original light gun on modern display (or a blank spot on the wall, whiteboard, map, cloud, etc.)!
    Might need to add an IR pass filter to the gun.

    1. Yeah, one would think this would work, the trouble is in the original code; Unlike the C64 which would actually work the way you suggest, and likely quite well to be honest; The NES actually relies on a flash method, instead of watching for the electron beam to sweep the lines and keeping track. It’s really more of a timing issue, but thankfully one that has been solved, and maybe our kids will get to experience the frustration of uselessly shooting a mocking dog.

        1. I read that in the article too, and it didn’t make sense. “15kHz light” is in the radio band of the spectrum (i.e., not visible).

          If it means it’s sensitive to light flashing at 15kHz (the horizontal scan frequency) that might make sense, but I’m not aware of any photodiode that’s only sensitive to flashing light. It has a response time in the order of 10’s of scanlines, so the CPU isn’t able to do that filtering either (that’s more like what the Sega systems did).

          1. Actually, it is pretty common to use modulated IR signals. For example, our typical TV remote sends out modulated IR signals with 38KHz carrier frequency using IR LED and the photodiode in the TV will be processed by a 38KHz band pass filter.

      1. That’s interesting, I heard about the flash thing, too. I once read that the NES Zapper could be triggered by any bright light source, like a light bulb. I have no experience with that, though. I also wonder if this depends on the Zapper model in question. The NES had a lot of third-party peripherals being available to it throughout its lifetime.

        1. It CAN be triggered that way, yes, but the game does the check by first making the whole screen black, checking the sensor for dark, then each target in turn, checking if the sensor reads light in that frame (yes is a hit for that target).

    2. Be careful with that polygonal mirror. It will be spinning very fast. For instance, a 25-face polygon for NTSC will be spinning at (525/25)x(60/2)x60 = 37,800 rpm. You don’t want to be nearby if it spontaneously disassembles.

      1. Despite the speed of the mirror(s) turning pretty fast, syncing this mechanical device to the electronic signal of the TV is not impossible but is a challenge. Keeping it in perfect sync and perfectly stable at those speeds can be a thing. And a mirror out of sync with the video source will quickly result in a “game over”. The idea is pretty smart, but making it work reliably might be a frustrating and costly challenge.

        The alignment of the projected IR-screen is another issue, since you can’t see it yourself, but there are tools for that, one small issue, although the dot will be bright enough to be detected by the photosensor, the average projected IR-overlay image won’t be very bright if you look at it with a ordinary IR-enabled camera. But perhaps a slower speed for calibration in combination with a red laser might make that easier.

    3. If you’re going to go through all that trouble to make an IR raster scan in sync with the video, you might as well just replace the IR LED with RGB lasers and make yourself a laser projector.

    1. Not a troll, it’s a real story that came to mind. The clone console was a Supercom 72, in case you wonder. The Zapper it came with was cheaply made (very brittle, the button press very crunchy), so it’s no loss to collectors. And I’m from Europe, yes. In my country, lighters in shape of guns/pistols are no longer allowed, too, because they masquerade as a different object they are not. Just like wall clocks with a built-in spy cam do. So there was the possibility that I couldn’t even sell that Zapper online without getting into trouble at some point. That’s what worried me at the time, at least.

        1. Since you mention knifes, they’re forbidden in my place, as well.
          If they go past a specific blade length, I mean (~10cm max?). In public.

          So you basically can’t legally walk the streets while holding big, non-foldable knifes; while holding a butter knife at the street café is okay. Using a normal-sized pocket knife is okay, too.

          Other folding types may or may not be allowed to have a “snap” mechanism at some point. I’m unsure about that one. Hm.

          I’m sure the models with the blade “jumping out” on the front are forbidden, though.

          And chefs (cooks) must carry their knifes in a special steel box, which has a lock.

          Fishermen can carry a knife in public (at the lake etc) if they have a fishing license.

          But all in all, those little knife gadgets, which you can carry on your belt or your necklace etc are illegal, as well. In public, at least.

        2. Or, y’know, anything that’s toxic, flammable, can react with anything else, *can’t* react with anything else (but displaces oxygen), has any sort of unnatural effect, has any sort of natural effect… Humans are fragile.

  2. just stick an ir camera in the thing, put 3-4 ir led targerts around the tv. then you could figure where its pointing with a little bit of calibration data. you can go the other way with the targets on the gun and the camera on the tv. you can use free track and get the orientation data on the gun and then trace that into the screen.

    there is a more dumb way to do this. with a number of photocells at the corners of the screen, then reading the intensity of all four to interpolate the position. this wont give you a 3d vector but it will tell you if you line up in screen space, so its suited to 2d shooters.

      1. You can’t do an accurate light gun with just the Wii LED strip, because there are angles you can’t tell apart if all the LEDs are in a single line. There might be a way to do better if you add accelerometer data, but I doubt it’ll be precise enough for hitting targets without a crosshair in the game, which would just spoil Duck Hunt. (On the Wii, a cursor is generally used when aiming.)

        You really want four LEDs in a quadrangle, and then there is nice math for recovering where the gun is pointing, though a bunch of calibration is needed.

        A practical difficulty is that if your screen is too large, and the LEDs are on top and bottom, you have to be sufficiently far from the screen for the camera to see both sets of LEDs when your point at targets near the top or bottom of the screen. With our 43 inch TV and our sofa distance (maybe 8 feet?) it works with the Wiimote camera, but I suppose a bigger TV could be a problem. You might be able to overcome this by projecting the dots onto the screen itself.

        1. Thanks for sharing the link, it’s an interesting hack (of, I’m assuming given the handles, yours). Do you remember right now if and where the “confusing” angles come into play, especially when assuming user is pointing roughly at the TV in the first place?

        2. There are multiple projects out there already using ir leds. Gun4ir uses 4 ir leds in a + pattern while Samco uses a wii bar above and another below. Tracking in Gun4ir is spot on with or without crosshairs no matter where you stand while Samco is decent if you don’t move otherwise you need to recalibrate it often. Both can use a wide eye or fisheye lens to allow you to get within 1.5x to 2x the distance of screen width.

          There’s also the Lichtnarre project which uses the Wii remote directly but achieves much better tracking than what the Wii achieved and Aimtrak lightguns have been around for years though they suffer needing to be recalibrated often.

          On the other spectrum is the Sinden lightgun which uses a screen border and a webcam in the gun to calculate the crosshair position. It works quite well too.

    1. As mentioned by the other commenter, IR LED targets is how Wii Remote works, with PS Move doing the outside camera variation, and I think some of the 16-bit era light guns had a similar approach.

      The problem as presented in Nicole’s article – which, while still only implied by the entirety of the blog, may be more evident in the whole page than this summary – is that “we” are not making a new game here, and presumably want to preserve as much of the non-TV original hardware in the, uh, “playchain” as possible. If you’re going to replace the old photodiode controller with IR camera and a microcontroller that makes it appear like a photodiode to legacy software running HMOS 6502 knock-off, you might just as well replace your new TV with old one, or configure a PC/RPi/Wii/whatever to emulate everything.

      The problem as seen by the modern software entertainment business is that most of the market seems to be worn out on Wii, AND apparently someone pulled out a patent on the IR camera in the controller.

    1. The gun law in my country is very strict, unfortunately.
      A slingshot, as once used by kids, is being registered as a real weapon nowadays (at least, to my understanding, if it’s the “precision” model with an arm mounting).

      Same goes for a crossbow, as far as I know. At least the strong models and/or those models with a repeat function are considered as weapons of war. The simple, weak models may still be used for sports (not hunting), not sure. The law may change here.

      Anyway, for most weapons you need a gun license, which you must qualify for (police records are being checked etc).
      And the weapons can only being used in special areas, say a club.

      To be fair, shooting with bow and arrow isn’t so strictly being handled, as long as nobody is endangered, I believe.

      Though, I wonder how long it takes up until water guns are being affected by that law.
      You could use them as flamethrowers, after all. YT is full of such weird things. 🙁

      Another consideration is that some water guns may look too realistic nowadays.
      From the far, pedestrians or the police may think they seem real.
      That’s the big main problem with fake guns in general, maybe.
      In the paranoid world we’re living in right now this can lead to tragedies.

      That’s also true for the NES Zapper, maybe.
      Just imagine someone plays Duck Hunt in the evening, while the curtains are being closed and the lights are on.
      A neighbor or pedestrian walking by might be seeing the silhouette of a NES Zapper behind a curtain..
      But he/she doesn’t know that. What they see is a person’s hand is holding a long weapon:
      Since it’s very long and oddly shaped, it might have as well a noise canceler being attached to it.
      That would be an explanation to the witness why he/she didn’t hear a single shot.
      A worried person may totally think it’s a crime scene and call the police.

      Speaking of, when I was little, it seemed to me the policemen were a bit more relaxed here, less US-like than they’re now: they were less playing “cool” cop or demonstrating authority, but looked more like traffic policemen or forest rangers.
      They weren’t being armed so much all the time, either.
      Back then, I suppose, their work wasn’t being so internationalized yet (in EU, they try to unify things across the boarders) and they had a different training, I suppose.
      Back then, police vehicles didn’t have that annoying Kojak siren, either.. *sigh*

      The latter is something that’s hard to adapt to, really. Whenever you hear a Kojak sound, you think it’s a funny sound effect out of an American movie.
      It takes a while until you realize it’s a real police car and not a sound effects module of a toy car.

      But that’s how times are changing, I suppose. 🤷‍♂️
      I remember of when I was little, there was chocolate/chewing gum in cigarette shape, made for kids. It was a harmless fun. They’re either nolonger being allowed (in my place there was a law change in 2013 that banned chocolate cigarettes for a while, but it was an accident and had to be taken back?) or just fell out of fashion because they would glorify smoking (now uncool).

      Makes sense, kind of. The reason why we kids wanted them was because we wanted to mimic our parents, which were often smoking in these days.
      But since that is slowly changing (gratefully!) the loss of chocolate/chewing gum cigarettes is not a big deal, I suppose.

      Same goes for the gun thing, maybe. Kids wanted to be cool and mimic the older ones.
      That’s why those NES games like Duck Hunt came to be, maybe.
      It was a cultural/social thing of an era gone by.

      PS: my apologies for the long comment. I was just thinking out loud. A bit too much, maybe..

      1. The reason all this stuff is happening to you is because you (and people like you) sit there and take it, like a farm animal waiting in line at the slaughterhouse. I’ll never understand the mindset, honestly. Europeans are weird.

      2. When I was a kid, we played with an expended LAW rocket tube.
        It was our imaginary bazooka.

        ‘I killed you.’
        ‘No you didn’t, you missed’.
        ‘Bazooka! I smegged your whole squad!’

        In the park. Good times.
        Real cigarettes. Candy cigs were for babies. Like 3.2% beer.

  3. Oh you should get rid of all of your tools. You can use hand tools to make firearms. Having the ability to manufacture firearms must be giving you even more stress.
    While you’re at it you should get rid of all of your knives because you could use those to kill people too.
    You might want to get rid of all of your computers as well They allow you to simulate, design, manufacture and download blueprints for firearms. Not to mention all the other highly unethical things that go into manufacturing computers like child and or slave labor.(I’m not lying either looking to the supply chain) You should definitely get rid of all of your electronics. It would be far more ethical and you would feel much better about yourself. Also the power that they consumes is destroying the planet and will probably kill uncountable numbers of people over the coming years.

  4. I’ve wondered if it’s possible to create a custom LCD driver board with a fast framerate/refresh LCD panel to mimic the behavior of CRT closely enough to get it to work.

    If you had a 240Hz panel, you could in theory update the screen 1/4 at a time (with a sourcel framerate of 60Hz). E.g. once the 60Hz signal has gone through the first 1/4 of the picture, update the LCD with what you got and keep going. I’m not that familiar with LCD drawing characteristics, so it may be possible to update portions of the screen at a time for even faster updates.

  5. Now I am utterly confused… I thought the lightguns do not work on LCDs, because of the fundamental difference in the design: CRTs work with scanlines, while LCDs display the whole screen. And that is exactly what your other link (about the Duck Hunt) states…

  6. I have a light gun for the nes the works on a flat screen the way I got it working is at some point in time I found a comment that the light sensor in the gun has a filter built in it just for crts so the gun is blind to flat screens so I changed the sensor with another light gun one of the really cheap ones to fix that and found roms that somebody moded that gave you the option to change the time delay at the start screen I don’t remember there name sorry

  7. Note to HaD staff. When you delete an entire comment string, the little thing next to the headline that says the number of comments doesn’t get updated. This one still says 40 comments (there are currently ~20)

  8. The mechanism behind the Light Gun is the same as a light pen. The problem is modern LCD screens which includes modern smartTV screens is they don’t operate with raster scan process like CRTs. The closest thing I can think of is a type of Laser-scanning projector. There’s a product some years ago that is a laser based projector that generates the image raster line by raster line at high speed…. like a CRT. This could work. Light guns and Light pen waits for the raster beam to cross in front of the diode inside. This happens at lightning fast rate you can’t tell the CRT raster beam process. With a light gun, you can just point it at a light bulb and press the trigger… yeah…. kind of work but doesn’t really. Light pens works off the same process but is used to control a pointer or click on an image icon or something like that. How does it know where it is on the screen? It comes from raster line counter and precision timing on the exact point which pixels are being drawn the moment the raster beam is under the photo diode. It’s based on timing and a counter that’s snapshot into registers in memory and read by the software running. If the software or game code determines the corresponding location of the light pens is detected is that of say an icon or something in the game that when selected does something like in a menu. The problem with LCDs are, the image is essentially drawn at once with constant backlight. It is light the raster beam is everywhere on the screen at the same time not pixel by pixel, raster line by raster line. So it confuses the whole system. Basically it will behave weird. You will have to have some contrasting grid on one screen to sort of fake something to get something to sort of work to move something like a cross hair kind of like… sort of, an optical mouse.

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