First or Second Focal Plane?

[gbal]

Agreed-almost exactly the same applies to paper target shooting-though generally the distance is known-100 y,600y 1000y etc. Whenit isn't-laser rangefinder-the use of this is I think well agreed by all whohave to find variable ranges,except under severe time duress.

And for target subtension-exactly the same considerations-a fine cross hair/dot is best.

 

I should not think focal plane options have much of a role in close range shooting-foxing at night eg.

 

Maybe a little ore subjective is shot correction-in theory,it seems to me the system of mesurement is largely subjective-I judge by fall of shot-there is no other way-and if it's two marks down and one to the left,so be it-you either hold two marks up and one to right,or click accordingly.For the former,the unit-inch,cm or gnats hair -does not matter -it's two up ,one right. If your scope is not set at it's 'true'mag in a SFP scope,as it always is in FFP,it can be more complex making click adjustments,as they will be proportional to the mag setting.Sort of-but the first is the fast way anyhow.Target and varmint shooters might decide that they won't miss by such a margin that the first way is impracticable,or at least on balance is preferable.You can of course shoot at the magnification that gives one to one adjustment.

It's a genuine choice-as evidenced by the scopes shooters actually buy.

Let me state it this way-bullet splash gives your required correction in "two up,one right"-and that is what you adjust (two up,one right".....there is no precision or convenience or speed added or taken away by the base units you translate this into.(so long as they are consistent between reticule and turret,or -with even less chance of human error-within the reticule markings,and that manufacturing travesty just does not occur.)You do need the reticule markings,of course.Not all scopes of either persuasion will oblige-in which case-usually for shots that go high,you will just be estimating,as there may be no markings.(which is what you get with a single target dot/cross hair;and many duplex reticules are deficient-no markings.Not an FP issue-it snookers both equally....up a bit,right a bit less.)

 

There is some choice however as to which +/- you rate more important to your shooting,and neither system is superior on all criteria. The other differences-lack of higher mag power in FFP eg,are being reduced-though so is absolute mag power in SFP.If you shoot at fig 11s 500 yardsaway,that won't seem important,but if you attempt to shoot at and see the results at 800y rabbits,0r 1000y 5 inch discs,it might.

 

gbal

[SWShooter]

The utility of ffp for shooters is NOT in their use in rangefinding.

 

This is a fallacy that is routinely trotted out and has become a truism. Rangefinding with a mil ret is a measure of last resort when all other tools, systems or aids are non functional, unusable or lost.

It's hugely inaccurate and a measure of absolute last resort.

 

 

FFP's actual utility lies in the fact that it enables the shooter to measure his fall of shot at any magnification - as an angular measurement; and then apply that same angular measurement directly to his turrets with no maths, no thought - nothing.

 

Regardless of range, and at any and all ranges, simply 'See 0.9, dial 0.9'

 

The key feature in understanding that utility is understanding angular measurement - be that mil or moa.

The key consideration in making sure you can make use of that utility is to ensure the units on the turrets match the units on the ret: mil/mil or moa/moa - and of course that the scope is ffp, in order that your measurements are correct at any mag, not just one.

 

This is widely and hugely misunderstood, but actually a hugely simple concept.

 

Mr Thicky here , so with a FFP if I find myself shooting 2" low at say 300 yards and my scopes is in 1/4" clicks I would click 8 up and then the same as if I was 2" low at 100 yards ?

[Shuggy]

Mr Thicky here , so with a FFP if I find myself shooting 2" low at say 300 yards and my scopes is in 1/4" clicks I would click 8 up and then the same as if I was 2" low at 100 yards ?

With FFP scopes with matching reticle and turrets (MOA/MOA or Mil/Mil) you should forget linear distances on the target. They are essentially irrelevant. Once you realise that your reticle measures an angle, you realise that you only need to dial the appropriate angular correction. So if you measure with your reticle that the strike is is 1 MOA low, you then dial 1 MOA up. The beauty of FFP is that this works at any magnification and at any distance.

[gbal]

Shuggy ,agreed.

Supppose now I did not have a degree in maths,and your first three sentences were not there,or I don't understand them.

I shoot and note that my fall of shot is 1 and a half cross hatches low on my scope reticule.

So I hold on the target one and a half cross hatches high on my scope reticule.

Were does my second shot strike?

The intended target,I think.

 

Note I have made no reference at all to focal plane,magnification,or turret/reticule consistency,or the units used. It's been fast and my second (hit) has been fired at the same mag as I chose for my first shot,presumably the mag I wanted. Exactly as your shots,except faster,and no potential error in dialing up,or redialing back/forgetting to do so.

 

So where is the advantage/disadvantage in FFP/SFP in (your) above secenario? Seems to be about the same,to me;if anything in hunting scenarios I have the edge (unless you have a patient quarry,and can get a draw.And a zero stop,to dial back to.Don't forget,now, before you engage the next target.

 

If your advantages need some maths,perhaps in other real-not theoretical scenarios,you may assume I have some, but please be clear just how non FFP would be disadvantaged,just as I have suggested FFP might be above (assume my reticule is sensibly hatched,and consistent with turrets-I think we can all accept that now,whatever the unit. Consider the context too-all too frequently,I'd say rather typically,where fall of shot is not seen-seems to me both systems are then embarrassed,big time).

 

gbal

[Shuggy]

You're quite right and indeed, that is how many target shooters hold for wind once they have found their zero at a known range. But if you want to rapidly hold over for different ranges then FFP is better, because the holdovers will work at any magnification.

[SWShooter]

With FFP scopes with matching reticle and turrets (MOA/MOA or Mil/Mil) you should forget linear distances on the target. They are essentially irrelevant. Once you realise that your reticle measures an angle, you realise that you only need to dial the appropriate angular correction. So if you measure with your reticle that the strike is is 1 MOA low, you then dial 1 MOA up. The beauty of FFP is that this works at any magnification and at any distance.

 

Got it.

[SWShooter]

There`s an interesting discussion here on FFP and SFP (along with some bitching) http://www.sniperforums.com/forum/optics/32464-argument-against-first-focal-plane.html

[brown dog]

Shuggy ,agreed.

Supppose now I did not have a degree in maths,and your first three sentences were not there,or I don't understand them.

I shoot and note that my fall of shot is 1 and a half cross hatches low on my scope reticule.

So I hold on the target one and a half cross hatches high on my scope reticule.

Were does my second shot strike?

The intended target,I think.

 

Note I have made no reference at all to focal plane,magnification,or turret/reticule consistency,or the units used. It's been fast and my second (hit) has been fired at the same mag as I chose for my first shot,presumably the mag I wanted. Exactly as your shots,except faster,and no potential error in dialing up,or redialing back/forgetting to do so.

 

So where is the advantage/disadvantage in FFP/SFP in (your) above secenario? Seems to be about the same,to me;if anything in hunting scenarios I have the edge (unless you have a patient quarry,and can get a draw.And a zero stop,to dial back to.Don't forget,now, before you engage the next target.

 

If your advantages need some maths,perhaps in other real-not theoretical scenarios,you may assume I have some, but please be clear just how non FFP would be disadvantaged,just as I have suggested FFP might be above (assume my reticule is sensibly hatched,and consistent with turrets-I think we can all accept that now,whatever the unit. Consider the context too-all too frequently,I'd say rather typically,where fall of shot is not seen-seems to me both systems are then embarrassed,big time).

 

gbal

 

The advantage in the case of FFP is that you have the choice:

Aim off or dial exactly what you see (mil mil or MOA MOA) (When? Ever zero your rifle?! Ever spot a consistent elevation change when plinking or target shooting at long range?).

THERE IS NO MATHS INVOLVED IN DIALLING WHAT YOU SEE!!

[brown dog]

 

The advantage in the case of FFP is that you have the choice:

Aim off or dial exactly what you see (mil mil or MOA MOA) (When? Ever zero your rifle?! Ever spot a consistent elevation change when plinking or target shooting at long range?).

THERE IS NO MATHS INVOLVED IN DIALLING WHAT YOU SEE!!

 

I suppose, I should add the other massive advantage of FFP: Unlike SFP, the zero cannot mechanically wander when changing zoom setting.

[gbal]

Shuggy/SWS : My interest is just in trying to undersrand what might be real advantages,though limited perhaps,for specific uses....I suspect many do not understand the maths etc,nor actually need to-but on both sides too many 'advocates' simply repeat mantras (it's the same at any mag/reticue too thick ...and so forth,which are variably true,but not operationalised into a meaningful context,or simply inaccurate-reticules eg can be suitably designed. With probably £10k in scopes,I'm interested in wheher further investment makes sense.

WE seem to agree that if shot fall is seen,the FFP allows direct compensation via the reticule (two marks low,so hold two marks up),FFP will do that,too,but much easier dialing the correction on the turret. (Interestingly,fixed distance targe shooters do tend to hold off,once dialed in-presumably as there may be continualy wind changes needed,and dialing is either slower,or potentially error prone.

OK .If there are likeely to be multiple target acquisitions needed with some time pressure at different distances- the FFP advantage would seem to be 'any mag' will do,while the SFP has to be set at it's one true mag.How big an advantage this is,I don't know-especially as this seems a 'precision shooting' type scenario,where magnification tends to be moderate (ie not above 25x-but SFP does give up some choice of mag. If fast is needed,the fall of shot will be better,anyhow.Turret turning is a likely source of error-especially without zero reset options.

"Ranging" I think is now accepted as a bit of a non event-Laser is the way to do that. I accept that the FFP can be used,IF size of target is known,and there is some mental arithmetic/calculator available,but error is likely (target height in yards x 1000/mils on reticule = target distance yards.

Fine for a 6'man,and 4 mils 2X1000/4 = 500

How about 10 inch gong,1.4 mils 10/36 X1000/14 =...calculator needed,please wait.

 

I can see some scenarios where the FFP has an edge,and just as many where it's features don't,and may be somehwhat unrealistic in the real world. NO-one so far has really made a clear case for the 'theoretical' points -or rather,I haven't seen such-plenty of repetiution of 'angular measure' and such like,'same ratio' etc...without as yet,a clear presentation of what those specs actually offer in actual shooting scenarios.The other 'side' repeat possible,but non general, disadvantages -equally unsatisfactory to the general case of optimum design in either format.

 

Practical/precision gong bashers seem to like FFP;Target Shooters SFP; Stalkers SFP: Varminters maybe either,more SFP? Suggests only that different kinds of shooting suit the different options....

 

It could be worse-and a whole lot better,if realistic detailed examples were more forthcoming,to allow informed choice. At least it's better than the 'allows faster shooting'...(short actions,straight pull etc)...no,may allow fractionally faster reloading,but makes no inroads at all into the 6 or seven seconds it then takes to realign and aim and ffire....real advantage-effectively zero. (the Norwegian fast shooters would prob not be slower with alternates to their bolt actions).

In a nutshell,what real world reasons are there for either FFP or SFP,spelled out,for the likes of me,hard of acceptance of slogans that just repeat 'specs',and ignore assumtions and reality (you often don't see splash cllearly enough...or why is 'fast' being used when not critical...etc etc).

What can I do with a FFP that I'd actually want to do,ditto SFP; AND that the alternate can't do-that is too often omitted. ( I don't shoot men of any size).

gbal

[SWShooter]

 

I suppose, I should add the other massive advantage of FFP: Unlike SFP, the zero cannot mechanically wander when changing zoom setting.

 

Certainly an important point, many cheaper and some "top end" SFP scopes are reported to wonder.

[gbal]

Certainly an important point, many cheaper and some "top end" SFP scopes are reported to wonder.

OK,if that is so-not many tests have found it,but is this not a 'quality' of manufacture issue,raher than an intrinsic feature of the two designs.SFPs need not wander- very cheap ones sometimes did.FFP reticule were sometimes to thick/thin.But neither need do so-not many scopes would be confidently literally thrown around as NF did,but that attests NF quality of manufacture- perhaps important,and desireable but only that-not that eg their glass is clearer. Maybe a Hensoldt at x2 price?Same point.

Any scope can malfunction-we'd need some real good data to see if FFP and SFP ( of similar price etc) really do differ in mechanical integrity under normal -or indeed any-conditions.

 

gbal

[brown dog]

Any scope can malfunction-we'd need some real good data to see if FFP and SFP ( of similar price etc) really do differ in mechanical integrity under normal -or indeed any-conditions.

 

 

George, do some reading to learn why, for basic optical reasons, wandering zero when zooming is not a mechanical precision issue for FFP (but is for SFP).

[ds1]

Shifting poi with 2fp scopes is due to reticule location relative to the zoom system. The zoom system requires some tolerance for it to work plus more tolerance for it to work though temperature changes as scopes expand and contract.

 

In fixed power scopes it does not matter which plain the reticule is in as there is no zoom system - a tube within a tube - to bugger things up.

[gbal]

David,thank you-a concise and informative summary.*

 

OK, FFP scopes have a potential advantage- there seems no evidence that it is much of an advantage in practise,given good scope construction (as with anything,badly done is a recipe for problems whatever the design etc).

Most of the scope issues on this forum tend to be upper end,often FFP (it's posssible the Leupold SFPs just get fixed with the lifetime warranty,of course,and we seldom hear of them. And that most UKV posters don't go for the cheap end stuff.

Let's add in the increased complexity of FFP though( ie more expensive stuff to go wrong?) -and the usual purchase price premium. Is there really much in it in the individual case over seasons of use? (Seems no data-and conditions of use vary-Precision positional shooting is rougher/tougher on scopes than Bench Rest,or most target shooting.)

HOw do the Precision guys rate scopes-the best test is probably Precision Rifle Blogs' Tactical Scope review-pretty well done.

The most important criterion for such shooters was mechanical integrity.Most scopes were FFP,but the NF ATACR and 5.5-22 NXS (both SFP) were immediately above and below the S&B 3-27 in the middle of the field. FFP were more prone to 'tunneling' at low mag-even the S&B,which was 'excellent' above 10x,the S&B did not track well mechanically (1/2 click out at 5 mils,1 click at 10 mils).The PM115-25 was excellent -best overall. (so there are within high end manufacturer differences-bear in mind all the differences here are really quite small-they are all very good scopes.The budget end may well be considerably poorer-as with most mechanical manufacture). The lower overall placed scopes (Vortex,Valdada,Bushnell Elite and...March(!) had around 1% mechanical tracking error (March was 2%).

NF asked about erector movement/click admitted to .007"/click-ie a hair's breadth.

NF ATACR (SFP was 'perfect' and very close second to PM11 overall winner) was 'perfect',and the S&B 'nearly perfect".

Leupold Mk6 (SFP) was 'perfect' and NXS 5.5-25 (SFP) 'nearly perfect'

 

These four are very ,very close/good. Samples will likely vary a little.

Is it reasonable to conclude,within the test parameters,that well made SFP scopes are not disadvantaged in mechanical integrity wrt FFP scopes?

 

"Optics thoughts" "HighEnd Tactica Scope Test" found the March Tactical SFP 2.5-25 had 'perfect adjustments';" superb,mechanically the best design ever used". The tester expected the FFP version to be the same.Fair enough,but it again supports the view that made right,differences between FFP and SFP on any mechanical crirteria are likely to be very small.....approaching zero ?

 

There are of course other considerations for other uses.Horses for course to put it uber technically.

 

When NF threw their new scope around fairly dramatically without obvious damage,it too suggests well made scopes are pretty robust-but that was a demonstration,not a rigourous test like the Precision Blog.

 

I didn't see anything in Barnsness ""Optics for Hunters" (DEVA-German National Test INstitute) that disagreed with the 'quality construction matters' conclusion. That's not to say everyone needs a £2k + scope. But all the scopes were good,if 'top end'.

g

 

* since it's still raining,here's one of the fuller descriptions I found,really just padding David's a bit.

 

" In some cheap SFP scopes,as the power ring is rotated,so rotating the zoom tube,it can shift the position of the reticule very slightly,with POI wander.This happens because the zoom tube rotates around the reticule "cell"(?sic). How much,or whether it happens at all,deepends on how well fitted the internal parts are.In a FFP scope,this can't happen because the reticule is located on the objective end of the scope,so the zoom tube can't influence the reticule positon.

It all depends on the precise/tight tolerances of the moving parts,the mechanical dependability. Almost any quality SFP scope won't have a problem but it is more likely in SFP than FFP"

 

S0,there is both a general design principle,and a manufacturing quality issue.There are of course,other issues the designs bring in-bottom line seems on this,that if made proper,it's no big deal. Cheap anything in scopes does degrade performance(though not proportionally,always.)

 

My next scope might be an FFP ( just to find out,as it all seems rather subjective),but I'll keep the SFPs too,as no persuasive advantage has yet emerged,but might, for my useages-everything except CQB).

[The Gun Pimp]

 

I suppose, I should add the other massive advantage of FFP: Unlike SFP, the zero cannot mechanically wander when changing zoom setting.

Has anyone actually experienced this? I always used to test for this when reviewing scopes but I never found one that failed the zoom test - even cheap Chinese scopes.

 

I have heard others mention it and I tried it with the new Leupold 7-42 and the new Sightron SV 10-50 - they were both spot-on. The biggest problem is getting a repeatable aim-point at the lowest mag setting.

 

In reality, I doubt that anyone would zoom from 7x to 42x between shots anyway.

[brown dog]

Has anyone actually experienced this? I always used to test for this when reviewing scopes but I never found one that failed the zoom test - even cheap Chinese scopes.

 

I have heard others mention it and I tried it with the new Leupold 7-42 and the new Sightron SV 10-50 - they were both spot-on. The biggest problem is getting a repeatable aim-point at the lowest mag setting.

 

In reality, I doubt that anyone would zoom from 7x to 42x between shots anyway.

 

Vince, I doubt most shooters notice it; as you say, most shoot at a fixed mag without changing it; nevertheless, in a target shooting environment where spotters are permitted it's my limited experience that most expect to miss with their opening shots - with no cause or reason to wonder why the opening rounds went mildly adrift - reasons which may or may not have included magnification changes to an SFP scope.

[brown dog]

Some old US Optics wordage on the topic that's nice and clear:

 

 

 

Question: What are focal planes and what is the difference between putting the reticle in the front or rear focal plane? Answer: Only in a variable power scope is the reticle placement a major problem. In the rear focal plane, or behind the power changing lens system (erector tube), was the first solution that occurred to optical engineers, and most American scopes are still being built that way. Unfortunately, this apparently ideal solution has a very serious flaw. Any tolerance change in the centration of the lens system and their spherical/longitudinal movement with the power change, will shift the point of impact. A variation of one thousandth of an inch will move the zero point approximately one inch at 100 yards. Since the mechanical parts that hold the power changing lens system slide inside each other, (some allowances are made for temperature changes, manufacturing tolerances and wear), there must be some movement made to accommodate this. Consequently this lateral and vertical movement will often shift zero by as much as several inches as power is changed.

A better solution is to place the reticle in the front focal plane, or ahead of the power changing lens system. The movement of the erector system will, optically, have no effect on the point of aim here. So why don’t all scope manufacturers build them this way? The downside of this method is that Americans typically do not like reticles that grow in size when the power is turned up. There is no actual growth in the reticle size. As the magnification increases, so does the reticle along with the objects in the field of view. A one inch dot reticle will still be one inch, at any power, be it low or high. It is only the appearance that is altered. If the power is turned from 2x to 4x, or doubled, the size of the objective image is doubled, and so is the reticle along with it.

Since the front focal plane reticle is a superior aiming device but aesthetically not very popular, there is only that problem to overcome.

[gbal]

Matt,you do a decent line in German one liners:How does

 

"Vorsprung durch Technik"

 

sound as a summary of improvements in scopes- "the March of progress" ? Reviews that find 'perfect mechanicals' may be a tad overstated for both systems,,but is there still a "major' issue with the bits inside top end scopes?

[brown dog]

Matt,you do a decent line in German one liners:How does

 

"Vorsprung durch Technik"

 

sound as a summary of improvements in scopes- "the March of progress" ? Reviews that find 'perfect mechanicals' may be a tad overstated for both systems,,but is there still a "major' issue with the bits inside top end scopes?

 

In this case, knowingly choosing the inelegant technical solution is hardly technological advancement!

[gbal]

But if the SFP scopes are indeed as good as the reviews and much useage-by quite savvy and demanding,and not blind- competition shooters suggest,then another differentiator between the two options has to go.....

Each focal plane arrangement has its pros and cons. Best to be accurate about the contemporary examples..There has been quite enough erroneous,or misleading 'information"in the past. At $7000,the Hensold is not perfect,at least in the Precision blog tests,but I'd be very happy to learn from it.Just the thing for a Ruger 'precision' rifle.And a BEAST for the Bat,or an ATACR-but Bat 'n' BEAST is phonetically more elegant. :-)

gb

[chaz]

 

I suppose, I should add the other massive advantage of FFP: Unlike SFP, the zero cannot mechanically wander when changing zoom setting.

BD,

I'm quite new to the "game", so please can you answer a question for me?

If for arguments sake I have just zero'd my Sightron (SFP )S111 6-24x50LRMOA at 100 yards using 10x mag. Then turn the mag up to 24x and shoot at the bull, will my point of aim have shifted? If it does, (and apologies if I sound dim) why does it?

Another question. If I have the same zero as in 100 yards at 10x mag and upload those details to Strelok+. If I then increase the mag to 24x and shoot at a bull at say 300 yards, will Strelok+ now give me the incorrect moa adjustment as it was calculated at 10x mag?

Thanks.

[gbal]

But if the SFP scopes are indeed as good as the reviews and much useage-by quite savvy and demanding,and not blind- competition shooters suggest,then another differentiator between the two options has to go.....

Each focal plane arrangement has its pros and cons. Best to be accurate about the contemporary examples..There has been quite enough erroneous,or misleading 'information"in the past. At $7000,the Hensold is not perfect,at least in the Precision blog tests,but I'd be very happy to learn from it.Just the thing for a Ruger 'precision' rifle.And a BEAST for the Bat,or an ATACR-but Bat 'n' BEAST is phonetically more elegant. :-)

gb

ps isn't making a mechanical device ' functionally/technically perfect' an improvement,especially if it is indistinguishable in performance to a more "elegant" design. The 'simple clear words' are outdated,even if they once had a good point.

FFP may well have improved too-but don't forget that S&B bracketed by two SFP scopes in the mid field.

[The Gun Pimp]

But if the SFP scopes are indeed as good as the reviews and much useage-by quite savvy and demanding,and not blind- competition shooters suggest,then another differentiator between the two options has to go.....

Each focal plane arrangement has its pros and cons. Best to be accurate about the contemporary examples..There has been quite enough erroneous,or misleading 'information"in the past. At $7000,the Hensold is not perfect,at least in the Precision blog tests,but I'd be very happy to learn from it.Just the thing for a Ruger 'precision' rifle.And a BEAST for the Bat,or an ATACR-but Bat 'n' BEAST is phonetically more elegant. :-)

gb

Having a play with that $7000 6-24 Hensold last weekend. It suffers from what most FFP scopes suffer from - the reticle is too thick at max power. Also, the turrets - really strange - it was very difficult to turn just one division - it always jumped two or three. I know that sounds daft but it did - anyone else handled one?

[brown dog]

But if the SFP scopes are indeed as good as the reviews and much useage-by quite savvy and demanding,and not blind- competition shooters suggest,then another differentiator between the two options has to go.....

Each focal plane arrangement has its pros and cons. Best to be accurate about the contemporary examples..There has been quite enough erroneous,or misleading 'information"in the past. At $7000,the Hensold is not perfect,at least in the Precision blog tests,but I'd be very happy to learn from it.Just the thing for a Ruger 'precision' rifle.And a BEAST for the Bat,or an ATACR-but Bat 'n' BEAST is phonetically more elegant. :-)

gb

 

Nothing erroneous or misleading; just simple mechanical /optical facts that you don't like

 

As regards 'savvy & demanding competition shooters' , clearly, that would depend on the type of competition. If you're thinking of the more static disciplines, have a re-read of my point about most staying on a single magnification and getting spotting shots. Such shooters don't care about the negative, because it doesn't affect the way they shoot - and is significantly outweighed by their desire for a fine ret at max power.