ISO doesn’t always equal ISO.
On the Sony a58, in normal situations, ISO 200 and ISO 800 are pretty close to impossible to tell apart (without very close scrutiny)
But if you take out the blue and green light, that camera’s ISO 200 looks more like 800 (which would normally be fine) and the 800 now looks like 3200, which on that camera, can be pretty smudgy.
If you know the limitations of your gear, you know when to compensate, or use a different strategy, like I did here by opting to push the lower limits of my shutter speed rather than risk the inevitable fail of the higher ISOs
sony a58, 70-200f2.8