Why so much grainy and noisy ?

[Braineack]

Why I needed f/8 : for the background detail .. if I would shot at f/2.8 the background wouldn't be this clear or something ..

not necessarily.

You were what 20ft (6m) from the subjects? and another 1ft (.4m) from the wall detail?

F/8 at 20ft, gives you a working DOF almost 20ft (6m) itself.

Shooting the subjects at f/2.8 you would have still had a 6ft (~2m) working DOF for both the subjects and the wall to be perfectly sharp and in focus.

All other things being equal, you could have dropped the iso 3 stops to 200 and had the same exposure.



At the current display size on the web, the noise isn't even noticeable.

 

[bc_steve]

I looked at the full resolution image. I don't think it's too noisy at all. My only complaint is that it is underexposed, otherwise it is quite a nice photo.