ISO Question regarding A7

[Redman12]

Hi there, I'm a new Sony A7 user and just wondered why when on manual settings, when I crank the ISO up to max it doesn't effect my live view monitor for example when I have my iso on 800 it previews exactly the same image on my live view as it would at a higher ISO. Is there a setting that I have missed which will allow my change in ISO to affect my live view, it would make life so much easy framing astrophotography shots. Thanks so much and hope this doesn't sound too newby.