Tap and hold to create a new filter and you will see a window appear in a different wavelength of light. You can reposition a filter by dragging it from the middle or resize it by dragging the edges or spreading it outward. If you make it big enough it will automatically fill the screen. To return to the default wavelength, just tap and hold to create another filter and then make it fullscreen. To close a filter, either flick it off screen or tap outside the filter area. You can also change the wavelength by twisting the filter. Available wavelengths include Gamma Ray, X-Ray, Ultraviolet, Visible (default), Hydrogen Alpha, Infrared, Microwave and Radio. Information about each wavelength is available by tapping on the informational title that appears briefly when creating a filter.