Originally Posted by kc
I have a few Scopes with a Parallax Adjustments and I keep them set maxt out,
what good are they? Do they help in low light conditions? or what?
Since this is the long range hinting group you're using them correctly. Just leave them set at infinity and the maximum parallax error your scope can have at the target at any distance is equal to the radius of your objective lens. For a 50mm scope that's about 1 inch. If you leave them adjusted for less than 2/3 the range you're shooting they can allow more error. Realized that how much parallax error a scope WILL have is a function of how well you center your eye with the exit pupil of the scope. The maximum error is a function of how far your eye can be off center and can still see the target as well as the amount the image if the target is out of focus with respect to the reticle.
An adjustable objective does nothing good or bad for low light conditions. The reason for a long range large game hunter to buy an AO scope is that most factory scopes are set for zero parallax between 100 and 200 yards which is far from ideal at long range. Some scope manufacturers will set the parallax adjustment of a fixed objective scope to whatever distance you choose for a modest fee.
The time you should not set your parallax adjustment to infinity is if you're zeroing your scope at a nearby target (50 to 200 yards). In that case set the objective focus for the actual target distance. That is the downside of having a fixed scope re-adjusted for long range.
Here's a simple description of what the parallax adjustment does in a riflescope.
Parallax in Rifle Scopes