Tag Archives: Image noise

High ISO and Noise Reduction

by Paul Schmitt

The digital photography has opened a new era in low light photography.NR fig 1 bunny  In the film era, high ISO speeds meant grainy images. Not so now! Mike Goldstein and Paul Schmitt addressed the subject at our December meeting, first showing the increased noise in a scene as the ISO rose, and then using Lightroom to remove noise. Discussion re- vealed that many are unfamiliar with this and miss the opportunity to boost ISO enough to gain fast shutter speeds in low light. This is key to good subject sharpness. So, we will revisit this. The image at right has a wide range of tones from dead black to soft whites. Image noise is analogous to the static heard on a radio when the signal is weak. Dark tones have a weaker “photon signal” and are noisier.

Let’s look at the image noise in a small portion of this scene as the ISO steps up in a Nikon D300S camera. From left to right they are ISO200, 800, 1600 and 6400. (206×308 pixel samples).

NR fig 2 4 image detailNoise first becomes slightly apparent at ISO400, with it clearly growing in severity at ISO800.  (Let’s use the highest ISO6400 so that the result is most apparent in the  limited resolution of the present format.) Continue reading High ISO and Noise Reduction