The White Balance Lens Cap uses a simple snap-on lens cap design to keep the cap locked firmly on your lens. Accurate white balance setting is as easy as putting the cap back on the camera, point the camera at the light source and then snap a reference image for the use as your cameras pre-set white balance reference. So, no matter how challenging the lighting situation, you'll quickly and easily get beautiful balanced images without the need for bulky reference cards or lots of time on the computer after shooting.