Unfortunately higher ISO values bring higher noise levels reduced sharpness , different limits different cameras.Faster , brighter lenses also generally expensive , powerful solution low light photography.Be aware though using lenses apertures f/2 wider also means little depth field , narrow plane sharpest focus.Subjects front behind zone witll progressively blurred.This may fine many subjects , little use buying expensive f/1 lens going use routinely f/8.ISO similar concept speed film.There fast films slow films fast ones showed high levels grain.ISO 400 far willing go.Now ISO values exceed many times , sometimes producing images low noise levels even values like ISO 3200 even ISO 6400.How far individual photographer willing go judged ISO shots publish part camera reviews .