Originally posted by vievetrick I knew I would have the answer quick if I posted it here. That was it!! :-) Thanks a lot!! About to head out for some night shots and wanted ISO 100 at least. Thanks again. I knew it was something I tweaked and just couldn't figure out how to get back.
Just to confuse you a bit more ...
ISO 160 with Highlight correction ON still is ISO 80 actually. But only parts of the image which would overexpose at Highlight correction OFF benefit from the low ISO properties. All other parts would be 1 stop underexposed at ISO 80 which is why the camera tells you to be at ISO 160 (which is wrong actually and the core reason you cannot switch to 80: you already are in 80...).
If you want to shoot with high dynamic range (like a night scene), you actually
may want to use Highlight correction ON with ISO 160 to get the
full dynamic range of ISO 80 but with the extra headroom shifted 1 stop from the shadows towards the highlights. There still is ample headroom in the shadows left and less blown highlights. Of course, nothing a simple EV compensation wouldn't do too ...