Following is a crop from a RAW shot, developed in Lightroom 5.7, into a setting sun from a Sony A77II – ISO 100, f/5, 1/20s, with a TTL fill flash.
In the darker regions near the sun a series of horizontal lighter lines can be seen. What causes these?
Here is the same image with contrast cranked up to make it easier to see the bands. Starting from an arbitrary band, I counted the number of pixels separating each successive band and got the following sequence: 18, 24, 12, 24, 12, 18, 24, 12, 18, 18, 24, ...
My guess is that it might be the sensor equivalent of lens flare, in which case the question would be: what is the physical characteristic of the sensor that is being illuminated?