Increasing the ISO setting on your camera may enable you to better shoot in low light conditions, but it will also increase camera ‘noise’. The image at ISO 50 looks quite clean, but at ISO 25600 a lot of the details are lost. Also note that noise levels will vary from camera to camera.
The higher the ISO value the noisier/grainy splotchier the image will be. Note the loss of detail especially in the darker/shadow areas.
Images for this article were shot with a Canon 5D MK2 camera. Results will vary between cameras.