Hmmm weird but you would think you will get more for new model but somehow Nikon lowered the low light performance of the D5600 compared to the D5500 and all other parameters seems identical.
Makes no sense why they would do that, I mean not a huge difference but I would expect to see a small improvement and not a small step backwards.
This was takes from the Nikon Rumors site
Nikon D5600 tested at DxOMark | Nikon Rumors
NOT much of a difference...I looked at their test results: Looks to me like this 1/3 stop differecne in one of their categories comes down to the actual ISO performance of the two sensors.
Look at these two screen captures I just made...the really, really CRITCAL results are the same...overall score, color depth, and dynamic range. Those are the most-likely scoes that will really show performance differences. But a 1/3 stop "fudge" on stated ISO values, and actual ISO performance? Ehhhh...this is not "a decline". Again, look to DxO Mark's own explanatory notes...
Set your ISO 1/3 of an EV differently...imaginary problem corrected.
View attachment 133426
As you can see in the screen capture I made, the D5500 has a teeny-tiny bit higher "actual" ISO value at 100,200,400,800. and 3200 ISO settings...and the sliiiiiightest bit higher actual ISO performance at the other four tested values. Voila!
View attachment 133427
Oh look at this screen shot I made--the D5500's 1/10 to 2/10 to 3/10 higher actual ISO value compared to the Nominal value means a whisker (or less) higher SNR across the range. Whoa! I would describe this as a totally expected result.
The most-minor of differences, at almost useless degrees of difference, across the entire ISO range between the D5500 and the D5600.
Orrrrrrr: this could be norminal sample to sample variation.