Schlieren-Videography

You can get better results, when the raster is aligned with the sensor-pixels of the camera. Already a tiny angle may worsen the result.

Just a quick idea of how to create a Moiré pattern using Inkscape.

1. Open a new file ( DIN A4 or what is your standard size)
2. Draw a square all over the outlines of the new file
3. Set it to no stroke, go to fill and set the color to black
4. Click on "pattern" and on "stripes 1:1"
5. Now there should the a stripe-patter

In the upper left corner you can see a square, a circle and a "x"

With the square you can change the size of the stripes, with the circle the rotation and with the "x" you can move it. Just click on the symbol of your desire and drag it around to change/move the pattern.

In this video I dropped some Salt into the water bath.

Yesterday I tried to do Schlieren in fluids and it works just fine!

As fluid tank I used an etching bath, filled with water. I placed it between the camera and the Moiré pattern.

To create some turbulence in the water I added some Isopropanol and later also Salt. Here is a video of the result with the Iso.

More and better results will follow soon!

As John King suggested here is a video with a new kind of calculating/getting the schlieren. instead of an steady reference image, I used the frame before the current one as reference.

This causes, that fast changes are visible but steady changes disappear, like the flame of the torch.

This one doesnt work out that well, so I will switch back to a steady image.

Here is just a little bit more about the working principle of what is happening.

On the right side we have our Moiré pattern and a light source. The light source is not explicit necessary, if you ambient light is bright enough.

On the left side is our camera.

As the Light now travels from our light source to the Moiré pattern it will be reflected. The dense air between the pattern and the camera will now "disturb" the light.

That is what we want to record, this disorder/interference of the light.

To do so we have captured a reference image of the pattern before and calculate now the difference of these two images.

Again, the bottle, but longer and better \o/

You can see the gas floating out of a fresh opened bottle.

Made a better setup and immediately better results. In the following Video you can see the results.

A lighter and a gas bottle.

Even if you think that your setup is perfect, it isn't. I just remade my setup and figured out which two things are most important.

Thing 1:

Light, you will need an even proper lightning, otherwise you may have a bad effect or even ghostings.

Thing 2:

A good distance, play with that, it took me serval attemps to find a nice distance.