To learn more out of ISO, do the following exercise.
1) Find a subject that has:
• Broad expanses of color, such as a fruit and vegetables at a farmer's market.
• Shadows or gray areas.
2) Photograph the scene at the lowest ISO setting, and at the highest.
3) Compare the two photographs by enlarging them.
• The color is more accurate on the low-ISO photograph.
• The high-ISO photograph has specs of inappropriate color, in the evenly-colored areas.
• The high-ISO photograph has specs of inappropriate brightness levels, in the shadows or gray areas.
• Inappropriate brightness levels are specs that are too light or too dark.
Note the poor quality of the color in the high-ISO photograph below, and the white specs in the dark background.
Use a low ISO to reduce noise.
You can also reduce noise by using noise reduction feature of Photoshop and Photoshop Elements, as well as other noise reduction software.
Newer cameras have less noise than older cameras.
Digital SLR cameras have less noise than point-and-shoot cameras.