D7500 has high thermal pattern noise
In an earlier post I examined the noise in single dark frames over a range of exposure times. My conclusion was that the Nikon D7500 was a lower noise camera than the D5300. This was also backed up by an examination of master bias frames that again strongly favoured the D7500.
However ...
The first image I attempted to produce with the D7500 exhibited very strong streaks in the noise.
I had been in the habit of not using dark subtraction with the D5300 as it has very
From the blog "Nikon D7500 DSLR for Astrophotography"
I read somewhere that the D7500 uses a two stage amplifier from around 400iso up. In order to see if this was playing a part I repeated the test at 250iso. The result was essentially the same - at around 20deg C, the D5300 has much less thermal pattern noise than the D7500.