Noise appears in dark areas when recording with S-Log.

S-Log2 and S-Log3 are functions optimized under the assumption that grading will be performed in the post-production process. Before grading, videos recorded with the S-Log2 or S-Log3 gamma have more noticeable noise in dark areas compared to videos recorded using other gammas. If the noise is still significant even after grading, it may be reduced by recording with a brighter setting and grading down to the appropriate brightness later. There is a corresponding decrease in dynamic range when you record with a brighter setting. We recommend checking the image quality including grading in advance by test-shooting when using S-Log2 or S-Log3.

For details on S-Log, refer to the page below.
Help Guide for Creators
https://helpguide.sony.net/di/pp/v1/en/contents/TP0000909108.html

NOTE: Help Guide for Creators is a Help Guide for more creative image production using a camera manufactured by Sony.