However , cameras , using lower ISO speeds going get detail , cleaner images.The lowest ISO speed , ISO100 , shows reduction dynamic range captured.Very fine detail starts drop around ISO1600 , noise remains well controlled , ISO12800 / ISO25600 , becomes damaging image.As ISO speed increased , noise also increases , could use ISO51200 ISO102400 really needed ( colour saturation remains good ) .Above images look awful , 's best use higher ISO speeds.One thing might worth noting , even highest ISO speed ISO1.6million , still read white text test chart , perhaps night surveillance , could useful , depending course , needs.When reviewed K-3 Mark II , said ISO25600 ISO51200 best reserved emergency use only.In comparison , K3 III gives vastly improved noise performance ISO25600 .