Low ISO sensitivity JPEGs
Because the sensor lacks an antialiasing filter, the images retain excellent sharpness even as noise rises. JPEGs look very clean up through ISO 800, and they're still quite good at ISO 1600. (Note: test shots at +0.7 EV.)
High ISO sensitivity JPEG
While ISO 3200 shows quite a bit of detail degradation, it's still quite good in well-lit areas, and many of my ISO 6400 shots were quite usable. (Note: test shots at +0.7 EV.)
Just like the D5200, the matrix metering on the D5300 tends to produce dark exposures.
D5300 vs. D5200, ISO tktk
The biggest difference between the D5300 and its predecessor tends to be sharpness rather than noise.
ISO 100 JPEG
The D5300 produces images with natural-looking sharpness.
ISO 200 JPEG
The lens and sensor resolve well together.
ISO 800 JPEG
The dark areas start to clip at ISO 800, but the details remain quite sharp.
ISO 1600 JPEG
You can see the noise reduction at ISO 1600, but there's little blurring of detail.
ISO 1600, no noise reduction
This is extremely fine-grained noise for a camera in this class. You can start to see the incipient hot pixels here, however.
ISO 3200 JPEG
The camera preserves detail very well even at ISO 3200.
ISO 6400 JPEG
You can get reasonable 13 inch by 19 inch prints from ISO 6400 images, depending upon the photo content.
Bokeh, 18-140mm lens
The lens produces very nice out-of-focus highlight areas.
The default color settings boost the saturation and contrast, but there's no egregious hue shifts.
I think the D5300 does a very good job of color reproduction.