In order to focus on aspects of capturing live performance I am going to assume of the reader a reasonable grasp of the fundamentals of photography. Especially the interaction of shutter speed, aperture and ISO. An excellent means of exploring this without having to raise as much as an eyebrow let alone a bulky DSLR may be found here. For good measure it also includes the effect of varying the focal length of lens and the camera to subject distance. You will need Adobe flash installed, which means that you can’t play with it on your iPad.
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