Full ISO 100 image, see the cropped (100%) versions below.
In-camera processing of JPEG files helps to boost colour and keep noise to a minimum. In this first shot at ISO 100, plenty of colour and detail have been captured. The image shows the five hills clearly defined, and the mist and trees can be easily picked out.
The same scene at ISO 200, and again the hills, trees and fields are clearly defined.
At ISO 400, the full frame sensor shows little sign of reducing the amount of shadow and highlight detail that is captured.
While the shadow and highlight detail of the image is retained, there is a slight softening of detail as the in-camera JPEG processing starts to suppress noise.
Looking at the flatter tonal areas of the back two hills and sky, you can start to see a further loss of detail, but colour and tone is still impressive.
At ISO 3200, colours start to wash out a little, and the noise suppression of JPEG files starts to lose some more of the finer detail.
Noise suppression in the background really starts to affect the flatter tonal areas.
While the noise suppression does minimise the effect of noise, the influence can just be seen on close inspection.
At ISO 25600, despite the smoothing effect of the JPEG noise reduction, the image is still usable with good levels of colour and tone. But the minor detail and contrast of the image is subdued.