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I have a laser and a container of water. Putting the laser beam into the water at a certain angle makes all of the laser beam reflected and none of it refracted, so no laser gets above the water. I wanted to take a photo with the lights off of such an experiment, but the results are extremely poor.

Here is a photo of my setup with light on:

Set Up

As you can see, there is no laser beam above the water: total reflection. How can I shoot a photo of such an experiment with the lights off so that the actual laser beam is visible? It looks really good in real life.

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    @Olivier the problem is probably then that I am using a very cheap, low aperture, non-configurable camera built-in camera of a low end smartphone. A professional camera would be better than my eye for sure but this is worse. I will add powder :) – Caridorc Jan 9 '17 at 20:33
  • Caleb's answer is the one you are looking for then :) – Olivier Jan 9 '17 at 20:37
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    You said above that you're using a smartphone so this probably doesn't apply to you - but if someone is trying to do this with a more advanced camera, the solution would probably involve using a tripod and taking a long exposure to pick up more of the light from the experiment. – Nathaniel Jan 10 '17 at 0:27
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    In my country photographers often use insense stick to take photos of light beams. It's also very common to take photos of sun light inside temples because there are already a lot of insense there to utilize. – phuclv Jan 10 '17 at 3:24
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    @Caridorc Probably because that information belongs in an answer, which you are free to write yourself, rather than in the question. – Michael C Jan 10 '17 at 22:48
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How to shoot a photo of such experiment with lights off so that the actual laser beam is visible?

The thing about a laser beam is that all the light is traveling in the same direction, so none of it is leaving the beam and heading toward your camera. If you shine a laser pointer at the wall, for example, you generally don't see the beam at all -- you only see the spot on the wall. If you want to see the beam, you need to add something to disperse the beam to the medium (the air in the room or the water in your tank) through which the beam is traveling. If you've ever been to a rock concert that uses lasers in the lighting, you probably noticed that they always use smoke or fog machines along with the lasers to make the beams visible.

You probably won't need to add much to the water to get the beam to show up brighter. It sounds like you can already see the beam with the naked eye, so it's possible that you just need a dark room and larger aperture and/or slower shutter speed and/or higher ISO to get a good exposure from the laser. But stirring a small quantity of some very fine particulate matter into the water will help disperse the beam and make for a much better photo. I'd start with very fine particulate like wood flour (like sawdust, but much finer), abrasive powder, powdered metal, etc. You might want to experiment with different additives, as you might get different results. For example, I'd guess that a very small amount of powdered mica would give you a sort of sparkly effect, whereas something that just makes the water a little cloudy (a little milk, maybe?) would give a more solid line.

One more thing I'd do to get the best photo would be to use a tank with very clean, clear walls, like a small glass fish tank. The plastic container shown in your photo looks rather cloudy, scratched, and just less attractive than it could be. Put a black sheet of black or white paper behind the tank, depending on what you want the background to look like.

  • "The thing about a laser beam is that all the light is traveling in the same direction, so none of it is leaving the beam and heading toward your camera. " not "none" because a little portion is hitting natural impurities in the water and bouncing back to all directions including my eye. – Caridorc Jan 9 '17 at 20:28
  • @Caridorc Yes, and the problem you're facing is that you don't have enough impurities. If the laser were traveling in a vacuum, you wouldn't see it at all. – Caleb Jan 9 '17 at 20:29
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    Sure. There are lots of things you could try. The main thing to be careful about, obviously, is that if you add something that changes the water's index of refraction, it might change the angle you need to get the total internal reflection that you're trying to illustrate. – Caleb Jan 9 '17 at 20:59
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    You can just add milk. Start with some drops and increase the amount. And yes... use a fish tank! – Rafael Jan 9 '17 at 22:34
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    Also turn off the flash on your phone! It seems like it was on for this pic, and its outpowering the laser. – smow Jan 10 '17 at 10:15
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I followed the advice in the accepted answer and added some iron powder into the water, so that the laser can reflect more hitting the impurities. The result is fine considering the very low quality camera and very low power laser I am using:

Laser

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You need to turn off the house lights and do a time exposure long enough to burn in the laser. If the water is clear it won't show up there either but only on the surface it is reflected/refracted towards. You'll need some impurities in the water to refract some light towards the camera. If the water is fresh from the tap it will likely have some air in it enough to refract, otherwise maybe try mixing in a tiny bit of cornstarch or salt or sugar to see if it will help.

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