Leaving your camera to Auto and you may find ISO settings go wondering…
For optimum quality and lowest noise, look to keep the ISO setting of your camera to between 80-200 (for compact cameras), and 80-400 for digital SLRs.
ISO relates to how sensitive the camera is to light intake, and most cameras will allow you to set ISO manually.
Once in Photoshop, when cropping, selecting and zooming in, noise distortion won’t be as obvious when these settings are used.
It’s worth mentioning, however, that ISO settings such as 100 are not always suitable under poorly lit scenes, as they require lots of available light.