When working in Manual mode adjusting aperture and shutter speed it is sometimes very handy to not have to worry about setting ISO in your camera. One way to set ISO is by setting ISO to auto mode. It is especially useful in low light. You want to use the lowest setting of ISO but setting ISO to auto with restrictions can really help and you can focus on the other two settings. Here is a short article that explains a bit of how to do that. Click here to read.