I wondered about whether optical centring actually gives you any advantage for a long time. I'd heard people say that it gives the brightest sight picture with less distortion etc etc.. but that didn't make any sense to me.
I'll explain why it didn't (and still doesn't). I think that theory is based on the fact that lenses tend to have the least distortion and the brightest picture when you look through the centre of them. That's true of camera lenses and very probably true of scope lenses too I would imagine.
Ok, here's the part that confuses me - when you adjust your turret, it changes the angle of the internal lenses, but it doesn't offset them. So if you look through the centre of the ocular lens, the light path through all of the lenses in the scope is still through the centre of all the other lenses through to the objective, just at a slight angle.
So you're not now suddenly looking through the centre of one lens and the edge of another, turning the turret doesn't offset them, it merely changes the angle of refraction. Yeah, that 'might' have an impact on brightness and flare etc, but it's likely to be very very small.
I then discovered something by accident, after I'd tried mounting a camera to my scope to take some through the lens type shots. It was a bit of a slap yourself on the head "doh" moment and I realised that optical centring will give you a significant advantage in terms of head placement and the reduction of the effects of parallax error. And that's going to be especially important for HFT.
I might write an article on the subject after I've done a bit more research into it and come up with some diagrams and photos to prove the point, but... for the time being, I'd say if you shoot HFT, optical centring is without a doubt (to my mind anyway) worth the effort and it's also worth doing for FT as well, but the difference isn't quite as important.
I'm talking about optical centring (mirror or v-block method) not just centring your clicks on your turret (which is largely worthless)