If you’re talking about JPEG, ignore everything I’m about to say. If you’re talking about Raw, that’s just not true. The D7100 is one of the best high ISO performers out there amongst APS-C cameras.
DxO’s SNR 18% data, which essentially answers the question ‘how clean are my midtones?’, shows the D7100 and 7D II are neck to neck.
Our own studio test scene shots here show that even when the D7100 gets 1/3 EV less light than the 7D II, it’s barely any worse in terms of amount of noise.
Compared to the G1X II & Sony a6000, despite getting 2/3 EV & 1/3 EV less exposure, respectively, the D7100 is better than both.
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work. 