Originally posted by MrB1 It might also be relevant here to mention here that using the lowest ISO value loses the ability to implement the D-Range Highlight Correction option.
The experts here will correct me if this is wrong but, If I have understood it correctly, D-R HC smooths the transition from brightness into blown highlights and works for both JPEG and raw files. So, if it is not set, more exposure care is needed when considering the right hand side of the histogram, as the scope for highlight detail recovery in PP might be quite restricted.
Philip
If enabling that (highlight correction), while extended ISO is enabled, it will automatically make the lowest possible iso to select 160, in order to use the last stop for the correction. If extended isn't enabled, the lowest ISO that can be used (with highlight correction enabled) will be 200.
Note that the K5 sensors actual base is 80, so I'd say it's unwise to NOT enable extended iso...you do get increased dynamic range and lower noise compared to iso 100 (although 100 is still very good so mostly just measurable differences, not always visible).