How or When to use Higher ISO setting

It might sound strange, but there are times when a high ISO setting is used intentionally to add noise, or grain, to the image. This is particularly useful when capturing black-and-white images in which you want to have an old-ish film look that simulates grain.

Another example is shown here. The ISO setting has been fixed to 1250 to make it more sensitive to light. As a color image it looks noisy , but after converting it to black and white in Photoshop and giving it an edge treatment, it has a very effective vintage look that would have been more difficult to achieve without the added noise.