DxOMark published their test results of the Nikon 1 J4 mirrorless camera ($597) that shows only marginal improvements compared to previous models:
If you are still wondering what was improved/changed in the Nikon 1 J4 camera, see this comparison with the previous J3 model:
Nikon 1 J4 compared to compact Sony cameras with 1″ sensor (RX10 & RX100II)
“We like the contemporary looks, small size, impressive AF and of course the system is maturing. Adopting the same sensor as the Nikon 1 V3 will certainly help the Nikon 1 J4 gain some traction with sales, given the price, but sensor performance isn’t as good as it could be and is really only on a par with some (albeit high-end) compacts.”
