<div id="linkdxomark">This a comment for <a href="http://www.dxomark.com/Cameras/Nikon/D5300">this page on the website</a></div>I am surprised that the D5300 did not test much higher on the DXO score.
Is the sensor tested by itself or in the camera?
Does the Expeed 4 processor factor into the results at all?
I've had a D5100, a D7000, and a D7l00.
The images I am getting with my D5300 are much better at ISO 12,800 than any of those were at ISO 6400 and even somewhat better than they were at ISO 3200.
As for movies, the D5300 is so much better that there is no comparison.
Sorry, I find that hard to believe.
I did develop a bunch of high/highest ISO images from dpreview and IR with ACR, and my findings somewhat contradict the DXO ratings.
a) Without any noise reduction, D5300 shows more chroma noise, in particular red blotches
b) With slight noise reduction, chroma noise clears up visibly better in D5300 than in D7100/5200
c) D5300 shows considerable color bleed using the chroma noise slider in ACR beyond a certain point (best verified in images with a color checker)
d) Detail retention was worse in D5300 at highest ISO. While the noise seems to dissolve better with noise reduction in ACR, objects seemed to "disintegrate", while D7100/5200 did a visibly better job "keeping things together" (for lack of a better word)
e) Banding/pattern noise is completely absent in D5300, no matter how much you torture RAW files in PP. D7100/5200 show banding at high/highest iso in dark areas.
f) At higher (highest) iso, D5300 images tend to look dull and grayed out in darker areas, which means I´d use the black slider in ACR quite a bit with the D5300.
g) Overall, ISO-performance of the D5300 seems to be in between D3200 and D7100/5200.
So, to me it´s a mixed bag concerning iso performance of the D5300. Testimages taken of color checkers and other flat objects can be wonderfully low in noise, but do not tell you much about more 3-dimensional objects with fine detail. Strangely the D5300 shows slightly more chroma noise without noise reduction, which however clears up much better with just a little bit of noise reduction, compared to D7100/5200. but that doesn´t seem to indicate overall better object representation at high ISO in the image.