Every photographer knows, the higher the ISO, the higher the noise in the photograph. Sure, we have come a long way & most of the modern cameras can control higher ISO’s with minimal difficulty producing cleaner photographs yet most of the photographers fear raising the ISO.
What happens when you do not raise the ISO? You either get an underexposed picture or you get a shaky picture since you need to work at slower shutter speed which may induce blur in the picture. There is no remedy for a shaky picture, no amount of post-processing would work here. For the earlier under-exposed scenario, you might bump up the exposure in post but then again you would get noise(In case you shot in jpeg, forget it if you’re under by more than a half a stop).
In such a case, where one needs high ISO to gain a good exposure, go ahead & raise the ISO. Sure, your picture would have noise(turn the in-camera noise reduction to reduce it & preferably shoot in RAW) but it would be exposed perfectly & won’t have any shake either since you should get a decent hand-holdable shutter-speed. The gist here is to not fear higher ISO’s but to embrace them. It’s much better to get a noisy but good photograph than to get a shaky one.
As Rick Sammon says, “If a picture is so boring that you notice the noise, its a boring picture”.