I just got my paper spectrometer and it works very well! This is the spectrum from an LED flashlight. When I analyzed the spectrum, I see the expected peak at 450 nm and another peak at about 540, but there is a dip at about 570-580 nm - there is no yellow, as you can see. I checked the spectrum with another spectrometer and looks normal, so I think the problem is my camera, an iPhone SE. Does anyone know if this camera is set to filter out yellow? Otherwise does the DVD diffraction grating filter yellow?