Have you ever noticed your picture to be a little grainy, regardless of whether it was clicked by a manual camera or a digital camera? Did you ever try to find out why under normal light conditions, when your lens is clean and the surroundings are not dusty, your picture still looks unclear or grainy?

If you notice the 1st picture on your left, you will see that it is very grainy and it seems like it has been clicked during snowfall or a storm. But that is not the case. Such kinds of noise or disturbances arise in your picture when you are clicking on a very high film speed. Film speed is measured in ISO and a film marked at 100 ISO is faster than a film marked at ISO 50. Film speed determines the sensitivity of a film. The higher the film speed, the more sensitive it will be. Digital cameras often have very high ISO values, such as the Samsung P1000 with 1,600 ISO. For while we increase film speed during shooting in low light conditions, we need to be cautious about the fact that the noise or grain in the picture increases as you increase the film speed.

For instance, see the table on your right. ISO 50 is least sensitive but it has minimum grain, on the other hand ISO 800 might help you to get the right exposure at constant aperture and shutter settings but it will have a very high level of grain. Hence it is always advisable to increase the speed of your stock when you are left with no other options of increasing the exposure by shutter or aperture, because a picture with the right exposure but a lot of noise is a bad picture. You can compare the picture above and see for yourself. So next time be cautious of the ISO settings or the speed of your film stock.