As can be observed from these images the grain is becomming appearant already at ISO 400. Still a reasonable grain
control is maintained up to ISO 1600. Beginning at ISO 3200 the grain is clearly visible. However, in situation where grain is not
an issue or the image is not intended to be enlarged beyond letter size even ISO 25600 can be an useful option.
images were produced with a Sony 16MP APS-C camera. The ISO performance varies among cameras, but the basic trend is similar
for most cameras with similar size image processor.