My Homemade Schlieren Imaging Setup

Using a parabolic mirror, the changes in air density changed the refraction index with the help of the parabolic mirror focusing all of the light through one spot into the camera's lens. 

I tried using a razor blade to adjust the contrast however, this didn't seem to work. Perhaps I'll come back to this experiment with better research and maybe that might explain what I was doing wrong in attempting to adjust the contrast.

Evidently, there is a clear difference in what can be seen between the two viewing methods. The hot air above the flame is much more visible in the (incomplete) Schlieren setup.