If you’ve worked with traditional photographic film rather than digital media, you will know how much effort film companies put into making the noise and grain almost invisible. Even fast emulsions now boast fine grain characteristics. It might seem odd, then, to introduce grain deliberately in order to add impact. But grain or rather the grittiness imparts is useful for adding character and mood.
Image by Sundancew
Grain works well on hard subjects: cityscapes, industrial scenes, rugged landscapes and portraits of men. It can conversely even be used with care to give certain shots a romantic feel. Noise and grain works best when it does not have to compete with vibrant colors; images with subdued color even mon0chrome are best.
Image by Todd Klassy
Adding grain can sometimes add anomalous colors. Sometimes this can add to the pictorial value of the image, but at other times you may wish to suppress it. Use the Monochromatic button in the appropriate dialogue box (if available) to add monochromatic noise to a color image.
Image by Hughes Léglise-Bataille
The JPEG compression technique introduces unsightly rectangular that become pronounced when the image is enlarged. Adding a little grain to the subject is a way of camouflaging this.