Thread: SWAROVSKI Z5 2.4-12 x 50

I know it won't be for everyone, but when trying to decide on the importance of adjustable parallax for a given scope/application I found it useful to crunch the numbers:

Parallax Error = (Distance your eye is off-centre from the scope)*(magnification)*(distance factor). The distance factor is (Target Distance - Parallax Free Distance)/(Parallax Free Distance)

Let's assume for the moment that with a decent cheek weld you can get your eye within 1mm of centre behind the eyepiece. Assuming also that this scope is parallax free at 100m (it would pay to check this, I haven't looked around thoroughly but I saw a forum suggestion that Swarovski set the parallax free distance differently depending on the reticle installed?) then:

Scope on 2.4x, target at 200m: Parallax error =1*2.4*(200-100)/100 = 2.4mm
Scope on 12x, target at 200m: Parallax error - 1*12*(200-100)/100 = 12mm

Scope on 2.4x, target at 500m: Parallax error =1*2.4*(500-100)/100 = 9.6mm
Scope on 12x, target at 500m: Parallax error - 1*12*(500-100)/100 = 48mm

A couple of notes to the above: 1) If the target range is less than the parallax free distance then the error figure comes out negative - but just forget about the minus sign and it still works. (2) The above equation works for when your eye is offset from centre up to a maximum of half the exit pupil diameter. Exit pupil is objective diameter (i.e. 50mm in this case) divided by magnification.

Play around with the numbers, estimate how repeatably you think you could get centered behind the scope in a hunting situation, and decide if you can live with the resulting parallax error.

Or you could just go ahead and buy what will undoubtedly be a very nice piece of glass and go shooting. That works too.