What do you guys think about the side focus scopes for parallax?? Am I nuts-I actually like the older style of the adjustable objective better than the side focus. Now keep in mind that I am left handed. So in order to focus I must take my trigger finger hand to adjust-rather than my off hand. And when varmint hunting I always use some sort of front rest, so my off trigger hand is not used for support while shooting.

I am going to buy a new varmint scope. And I definitely want a rifle that has parallax adjutment. I am leaning toward the VX-3---------4.5X14 for a 223 rifle. And it is available with both styles of adjustment.

I would like to leave price out of the discussion and just talk about what you guys think are the real pros and cons between the two styles. Thanks, Tom.

Well, me being left handed also I prefer the A.O. to the side parallax adjustment. I think the A.O. has a better depth of field, at least to my eyes plus there is no backlash when adjusting.

i'll take the side focus every time. i'm right handed and can easily adjust the focus while looking through the scope.

U.S. Optics will build a scope with windage knob and paralax knob on whichever side you want.

another point to remember is that side ao has one more glass element than front ao., which means the basic lens design combinations are different between the two scopes and could be the reason some people report a cleaner site picture. because of finer thread pitch front ao usually turn thru a greater distance and have more refinement in the final adjustment. Most side ao on better scopes, do not have backlash problems, tactical scopes in particular. Shooting large game animals, parallax is rarely a problem and most of the time the ao can be left on the more distance ranges, without a problem. The less the magnification range of the scope the less the problem, also as errors in parallax are magnified less.

Just as a point of clarification to Etoh's post ... there is no such thing as a "side ao".

"AO" stands for "Adjustable Objective"

When you have a scope that has a parallax adjustment, you either have a scope with an "Adjustable Objective Lens", or you have a scope with a "side focus parallax knob".

If you had a "Side Adjustable Objective" scope, you'd have a rather unique item, seeing as how you'd have an adjustable objective on the side of your scope.

I'll take the SF every time--just seems handier than cranking the front AO. I do agree that the front AO is a "smidge" more tunable. My 4200's stay at 100yds, and very seldom do I move them unless I'm out past 300yds, and the critter is a small one. Just my $0.02.

HOGGHEAD,

Recently I played with a Nightfore with A.O., a Swarovski with S.F. and a Bushnell with S.F.

For me the Nightforce was significantly easier to tune to see the lines on the sheet of paper than either of the others. Since you are left handed, it should be a no brainer: A.O.

It was mentioned the S.F. has one more lens. That could be why the Nightforce was noticably better than the other two in low light performance.

Another thing to keep in mind is if you use the flip up type lens covers like the butler creeks, the adjustable objective is almost useless. I like to keep the rain and snow out of the objective lens if at all posible and these flips up work nicely. The rifles that do have the parallax adjustment have the side focus because of this.

Not necessarily. My Leupold and Swarovski AO scopes don't spin the whole front end of the scope.

I prefer side focus; it's just more easier for me.

Maybe not for a lefty though. Dunno.

The only reason I can really see for using a A.O. would be if you are left handed. Side Focus scopes are waaayyy easier to use........................DJ

Side focus can be easily adjusted from behind the rifle. They are also reported to be tougher, i.e. take abuse better w/o zero shifts.
However, they have a shorter depth of focus which may not be a good thing under somne conditions.
The other thing is that once you find where to set an AO for various ranges, you can preset them easily unlike the side focus/parallax adjustment system. E

Side focus have a shorter depth of focus? Where did you here this? Is there some optical reason for this or is it another actual diamond coating on Leupy lenses sort of thing.

Can't preset Side-Focus to particular ranges? What a bunch of baloney. If you want you can focus them for whatever range and then make a little mark on the dial you can see from the rear, that way you can set the range focus without getting out from behind the rifle. Or better yet you can just reach up and focus it......................................DJ

I didn't read all the posts but this is it for me. Depth of field. The side focus scopes I have owned were the newer Leupolds, Zeiss and Nikon.

To me the best side focus was the Nikon Buckmaster.......

I have no clue to all the technical reasons just I know what I saw....

Dave

Daveh,



That might be one reason why the A.O. is easier to tune than the S.F. Although, I set my 4 1/2-30X50 on 150 last year in the woods and left it. Never noticed a problem.

I think Nikon uses a narrower field stop to enhance DOF on their side focus scopes. This gives that "tunnel vision" vignetting effect found in at least my Buckmaster 4.5-14x, and reduces FOV a little bit, but increases DOF across all magnifications (most notably on high magnification). I'm not sure if they do this in the non-SF Buckmaster scopes, which is where you'd really need a wide DOF, since parallax is fixed at one range. I suppose it's to allow the focus to be clear over a wider range of side adjustment?

some scopes like the 6x24x56 Diavari are very accurate in the ranges printed on ao knob and actual. However the increments in the calibration are too wide to be of actual use when compared to the 1 yd or meter of a LRF. Tunnel vision or vignetting is caused by the lens elements including the light from the end of the scope in the sight picture and show a design flaw. Sometimes this is seen more often on FFP scopes because of the need to focus on the front reticle. Front ao are easier to tune because of a finer thread pitch, and when combined with a greater radis in the tuning knob-- A best example is the big 50 schmidt and bender with the large side wheel used in field shoots. In opposition to the position that distances can't be read from the ao side wheel, this is exactly what this scope was designed to do. Depth of field is a function of non refracted light lens from lens, so a larger objective will have less depth of field than a smaller, all else being equal. The more parallel the light rays the greater the depth of field, that is the purpose of an iris. This also depend of the magnification. The more the mag. the less the depth of field. About 15-20 years ago Burris built a scope with an adjustable iris for exactly this purpose to increase depth of field on higher mag scopes for daylight pd hunting. Worked great.

I have found that AO allows me to focus with my left hand while holding the forearm.