texashuntingforum.com logo
Main Menu
Advertisement
Affiliates
Advertisement
Newest Members
PT2024, Graveaviat0r, Dave Harwood, Vinegarroon, Airborn_pmp
72208 Registered Users
Top Posters(All Time)
dogcatcher 110,823
bill oxner 91,416
SnakeWrangler 65,719
stxranchman 60,296
Gravytrain 46,950
RKHarm24 44,585
rifleman 44,461
Stub 44,419
Forum Statistics
Forums46
Topics540,148
Posts9,758,780
Members87,208
Most Online25,604
Feb 12th, 2024
Print Thread
First Focal Plane or Second Focal Plane, What's the difference? #3406566 07/24/12 08:53 PM
Joined: Apr 2011
Posts: 3,594
S
Skylar Mac Offline OP
Extreme Tracker
OP Offline
Extreme Tracker
S
Joined: Apr 2011
Posts: 3,594
This is something that has been brought to my attention, and I wanted to take the opportunity to clarify the differences.

I would have to say that now days most scopes that have etched reticles are in stalled one of two ways. First focal plane or second focal plane.

Now there is one manufacture off the top of my head that I am aware of that offers both first and second or what's known as dual focal plane, but the is the exception to the rule.

The primary focus of this thread is the difference between the two, first and second focal plane and how it can benefit the shooter.

First Focal Plane or FFP are very common among European manufactures like Schmidt and Bender, Swarovski, Zeiss, and several others. Although this is not always the case with American optics companies. It was not until in the last ten years that this became implemented in these optics.
Some of the reason is that this is more labor intensive as well as costly from a design and production stand point.

First focal plane riflescopes have the reticle installed just forward of the turret saddle just foward of the erector, this is to help control the magnification range of the scope.
What this means, is that as that scope goes through it designated magnification range the reticle will to change, or grow, becoming larger or smaller depending on what magnification the power selector ring is on.
The reticle is not actually morphing but it in fact maintaining its size relative to the sight picture or target image. This means that the subtensions stay the same.
With the subtensions staying the same throughout the disignated magnification range estimation, trjectory compensation, and zeroing can be performed on and magnification. This greatly assits in the utility of the riflescope.

Here is one of the best pictures I could find that helps illustrate where First Focal Plane reticles are located.


Now looking at a target and this is a concern for several people, is the image size of the reticle. Beacuse the reticle apears to change, they do not want a thick reticle, but it stays ralative to the target.




Now, riflescops with second focal plane are more readily available optics from American(Leupold and Bushnell) manufacturers as well as other manufacturers from overseas( Zeiss Conquest) because of they are easier to manufacturer. Scopes with FFP reticles will more often be found in scopes designed for long range tactical use and hunting applications.

In second focal plane scopes,the reticle is installed in the ocular bell, just on the aft side of the erector, past the leses that control the magnification of the sight picture or target image.
Since the reticle does not change in order to be relative to the target, the subtensions are only correct on a specific manification for range extimation and trajectory compensation. Typically the highest magnification.




Here is an example of how the reticle appears, not that both ends of the disgnated magnification range, the reticle appears to stay the same size.


There are always reasons why you should or shouldn't use something over the other. Although it is your descretion, and you will have to decide if utilizing one over the other will benefit you.

But I will say that when shooting long range I have found it more beneficial to make sure that everything matches.

The largest benefit to using a mil reticle is that you can use the reticle like a tape measure. Let’s say that you are engaging different targets and you reach a target that is 865 yards away. You then fire at a man size target and the splash indicates that you hit the abdomen area, but you were aiming for center mass. You can use the reticle to measure how far you missed. In this case 2 ½ mils. Your adjustment would be 25 clicks, since each click is .10 mrad. Now that you have assessed your DOPE you are ready to re-engage and hit the intended area.

A common misconception is that MOA and Mil are linear measurements. They are not.
MOA (minute of angle) is an angular measurement and so is (MIL) miliradian. It is a coincidence that when MOA is converted into a linear measurement that it subtends 1.047 inches at 100 yards. That is so close to 1” that most people consider it to be 1” at 100 yards. So a scope with .25 MOA adjustments translates to each click moving the reticle .25 of an inch at 100 yards.
However, the fact that 0.1 mrad is 1cm at 100 meters is most certainly not a coincidence. That is most certainly intended that way by design and comes out of the very definition of the angular measure of a radian and of the method behind the metric system. That is the beauty of the metric system: you can start with very few basic unitless measures and scale everything from there.

One radian is simply an angle where the subtended arc is equal to the radius. 1mrad is 0.001 of a radian, so 1mrad is an angle where the subtended arc is one thousandth of the radius, i.e. if an object at a certain distance from you subtends exactly 1 mrad, then the size of that object in linear units is almost exactly one thousandth of a distance between you and that object. What linear units you happen to use makes no difference. It will work with any of them.

It is simplest to use with metric linear units because of the base 10 scaling, of course.

With moderately retarded measurement systems we use for traditional reasons (like inches/feet/yards for linear units and degrees for angular units), translation between angular and linear measurements is a lot more involved.

Hence, between MOA and mrad, for as long as all you need to do is trajectory compensation, it does not matter what you use. However, once range finding is thrown into the mix, mrads are usually a simpler and more precise way to go.

If you can make your brain stop having to apply a linear measurement to your angular adjustments it is quite a bit easier to use a mil scope. You do this by using the reticle as a ruler to adjust for how much you missed the target. Say you are shooting 864 yards and you miss low, if you can see how much you missed then you put the reticle on where you were aiming and count how many mils it is to where your shot actually went. If it was 2.5 mils, then you just turn your elevation 2.5 mils in the direction you missed. It does not matter how far or how close you are shooting because it is an angular measurement. Mix matched scopes will soon be a thing of the past as it makes no sense to combine the two in one scope.


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: Skylar Mac] #3406765 07/24/12 09:58 PM
Joined: Mar 2009
Posts: 4,426
J
jeffbird Offline
Extreme Tracker
Offline
Extreme Tracker
J
Joined: Mar 2009
Posts: 4,426
Originally Posted By: Skylar@SWFA
But I will say that when shooting long range I have found it more beneficial to make sure that everything matches.


Absolutely. Excellent advice. Pick either Mil/Mil or MOA/MOA reticle and turrets, but avoid mixing and matching.

Originally Posted By: Skylar@SWFA
The largest benefit to using a mil reticle is that you can use the reticle like a tape measure.


Did you mean the benefit of using a ranging reticle of some variety? Whether the reticle is mil or MOA based should make no difference. For example, the same is equally true for MOA based reticles such as the Nightforce NP-R1 or MOAR.

fwiw - the argument by some, not necessarily you Skylar, of needing FFP to range at long distance on animals I find to be not compelling. The rate of error for ranging with a reticle is substantial for animals beyond a few hundred yards. As just an example, what is the height of the chest of a deer - if it is two years old vs. seven years old, or just different body sizes in general? If they are far off, can size even be accurately estimated in order to enable to the calculation?

For long range, the magnification almost always will be turned up high anyway, and a LRF will be, or at least should be, used for accurate ranging of the animal if it is beyond point blank range or outside of known distances.

Range estimation for a long-range shot on an animal is a different challenge than range estimation of steel targets of a known size in a match.

One other difference, which you pointed out, to me is one of the most important in a hunting application between FFP and SFP.

In the field, the FFP reticle size will "shrink" in observed size on low power and become "thicker" in observed appearance at high power.

In reality, if it is 0.1 MOA it will remain that thickness as an absolute measurement, but it will "appear" smaller.

SFP reticle size will appear "thicker" at low power and "finer" at high power, but the size of the reticle in relation to the overall view in the scope will remain the same large size.

This "observed" difference, especially at low power, makes some favor SFP for hunting scenarios so they will have a thicker & bigger reticle for low power scenarios and a fine reticle for high magnification.

Originally Posted By: Skylar@SWFA
However, once range finding is thrown into the mix, mrads are usually a simpler and more precise way to go.


While this is the most popular answer of the day, I respectfully disagree. To me, it is easier to do the math in my head of estimating a target size in inches, divide by MOA, and then deduct 5% than try to do the MIL math in my head. If someone can estimate a target size in CM, then they are similar calculations - CM/Mils = distance in meters. Easy enough. Using mils to estimate distance in yards based on a target size in inches? That is not as simple for most folks.

Also, most hash marks on Mil reticles are either 1 Mil or 1/2 Mil = 3.4 or 1.7 MOA respectively and MOA reticles are 1 MOA. By the same token, most MIL turrets are 0.1 mil ( = 0.34 MOA) per "click" as compared to 1/4 ( 0.25) MOA for most popular MOA based turrets.

With a smaller unit of measure per hash mark, isn't a MOA based reticle "more precise"?

Just offering some points for discussion, but a good and informative write-up overall. Nicely done. up






Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: jeffbird] #3407019 07/24/12 11:30 PM
Joined: May 2011
Posts: 1,444
B
beaucfus Offline
Pro Tracker
Offline
Pro Tracker
B
Joined: May 2011
Posts: 1,444
I use a mil dot master.



[Linked Image] [Linked Image]
Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: jeffbird] #3409400 07/25/12 06:27 PM
Joined: Apr 2011
Posts: 3,594
S
Skylar Mac Offline OP
Extreme Tracker
OP Offline
Extreme Tracker
S
Joined: Apr 2011
Posts: 3,594
Originally Posted By: jeffbird
Originally Posted By: Skylar@SWFA
The largest benefit to using a mil reticle is that you can use the reticle like a tape measure.


Did you mean the benefit of using a ranging reticle of some variety? [/quote


No,I touching base on the point of using the mil-dot to determine, how far off you are and making it do the work for you. Take for instance if your first shot is low and to the left.

No in most case mil-dot reticles are measured in mils, but there are companies that have moa reticles, like you mentioned NF, also Vortex's EBR, Sightron, IOR, and Premier.

The key is using the reticle to assist you.

Back to the shot though. Say your shot is low and left.
Use the reticle to determine how many mil dots low you. Say three mils.
The move your elevation turret three mils up.

Then evaluate your windage. And correct the adjustment for windage.

In a nutshell, it is easier when you have matching mechanics. Since everything matches there is no math invovled or trying to do conversions.


Originally Posted By: jeffbird

fwiw - the argument by some, not necessarily you Skylar, of needing FFP to range at long distance on animals I find to be not compelling. The rate of error for ranging with a reticle is substantial for animals beyond a few hundred yards. As just an example, what is the height of the chest of a deer - if it is two years old vs. seven years old, or just different body sizes in general? If they are far off, can size even be accurately estimated in order to enable to the calculation?


Sure, and I can understand that, but what about objectives that are closer?

I understand that you can be effective, with a SPF scope, but FFP is relative to the target, and the subs are the same.

Just because you build a long range rig, doesn't mean that you may not occasionaly see something that may come in close. This is the versatility of wild animals. Yes, they are creature of habit, and usually do the same thing and go to the same place. But occasionly the hunter changes. You may have a 15K acre ranch that you are hunting on and you have a LR rifle for that. But when your brother invites you to his place in the East Texas Piney's. Is your LR rig, still effective? Sure it is.

But I understand your view.


Originally Posted By: jeffbird

[quote=Skylar@SWFA] However, once range finding is thrown into the mix, mrads are usually a simpler and more precise way to go.


While this is the most popular answer of the day, I respectfully disagree. To me, it is easier to do the math in my head of estimating a target size in inches, divide by MOA, and then deduct 5% than try to do the MIL math in my head. If someone can estimate a target size in CM, then they are similar calculations - CM/Mils = distance in meters. Easy enough. Using mils to estimate distance in yards based on a target size in inches? That is not as simple for most folks.

Also, most hash marks on Mil reticles are either 1 Mil or 1/2 Mil = 3.4 or 1.7 MOA respectively and MOA reticles are 1 MOA. By the same token, most MIL turrets are 0.1 mil ( = 0.34 MOA) per "click" as compared to 1/4 ( 0.25) MOA for most popular MOA based turrets.

With a smaller unit of measure per hash mark, isn't a MOA based reticle "more precise"?

Just offering some points for discussion, but a good and informative write-up overall. Nicely done. up


I can empathize with that. In school we were not taught in detail about the metric system for measurements.

I remember inches.

I don't feel that MOA is more precise. Is it a finer measurement? Sure on paper it is, but your round doesn't fly straight.

Take the .50 because of the power or the 6.5X284 because of how slippery it is. They both still arc, thus the inplement of angle. MOA and MIL are angular adjustments to match your point of impact with your point of aim.

Great discussion. up ( duel )



Originally Posted By: beaucfus
I use a mil dot master.


They work very well and they are for both Mil and MOA.


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: Skylar Mac] #3409671 07/25/12 07:45 PM
Joined: Mar 2009
Posts: 4,426
J
jeffbird Offline
Extreme Tracker
Offline
Extreme Tracker
J
Joined: Mar 2009
Posts: 4,426
Originally Posted By: Skylar@SWFA
The key is using the reticle to assist you....
Then evaluate your windage. And correct the adjustment for windage.

In a nutshell, it is easier when you have matching mechanics. Since everything matches there is no math invovled or trying to do conversions.


Concur, but this is true whether the reticle and turrets are mils or MOA.

Originally Posted By: Skylar@SWFA
I understand that you can be effective, with a SPF scope, but FFP is relative to the target, and the subs are the same.

Just because you build a long range rig, doesn't mean that you may not occasionaly see something that may come in close.


Concur. If they are in close, things are simple rifle

Originally Posted By: Skylar@SWFA
I can empathize with that. In school we were not taught in detail about the metric system for measurements.

I remember inches.

I don't feel that MOA is more precise. Is it a finer measurement? Sure on paper it is, but your round doesn't fly straight.

Take the .50 because of the power or the 6.5X284 because of how slippery it is. They both still arc, thus the inplement of angle. MOA and MIL are angular adjustments to match your point of impact with your point of aim.


Not sure I understand the point you are trying to make. Please clarify.

Yes, both are units of measure of angle.

A MOA is a smaller unit of measure than a MIL.

How is a larger unit of measure more "precise" in this context?

In my experience, ranging an animal with a reticle beyond a few hundred yards is not very accurate regardless of whether mils or MOA are used due to the difficulty in accurately estimating the body size of the animal.


fwiw - I've used both FFP & SFP, mil and MOA based scopes.

I think we agree on some key points, pick a reticle that has ranging capability, make sure the turrets match, and learn how to use it.

To that, I add but also be realistic and take a good LRF and use the reticle as a backup, and pick one rifle with one load, practice often and be realistic how far a cold bore first round hit can be made.

We owe it to the animals to make humane shots on the first round.


No dueling from this end, just a friendly and thoughtful discussion.






Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: jeffbird] #3409722 07/25/12 07:59 PM
Joined: Apr 2011
Posts: 3,594
S
Skylar Mac Offline OP
Extreme Tracker
OP Offline
Extreme Tracker
S
Joined: Apr 2011
Posts: 3,594
Originally Posted By: jeffbird
Originally Posted By: Skylar@SWFA
I can empathize with that. In school we were not taught in detail about the metric system for measurements.

I remember inches.

I don't feel that MOA is more precise. Is it a finer measurement? Sure on paper it is, but your round doesn't fly straight.

Take the .50 because of the power or the 6.5X284 because of how slippery it is. They both still arc, thus the inplement of angle. MOA and MIL are angular adjustments to match your point of impact with your point of aim.


Not sure I understand the point you are trying to make. Please clarify.

Yes, both are units of measure of angle.

A MOA is a smaller unit of measure than a MIL.

How is a larger unit of measure more "precise" in this context?

fwiw - I've used both FFP & SFP, mil and MOA based scopes.

In my experience, ranging an animal with a reticle beyond a few hundred yards is not very accurate regardless of whether mils or MOA are used due to the difficulty in accurately estimating the body size of the animal.

Just as an experiment - try ranging an animal next season in an unknown distance area, do the math with the reticle and then check it with a LRF. See how far out it can be reliably ranged.

No dueling from this end, just a friendly and thoughtful discussion.


That is correct, both are angular measurements. However most people cannot get the linear aspect out of their head when it comes to shooting.

MOA and MIL are simply angular measurements not linear measurements. You and I are on the same page.

I am speaking of precise in the general aspect of, most manufacturers have a mil-dot reticle but they implement MOA adjustments. Take Nikon and Leupold for example.
Leupold has the Mark 4 with the mil-dot and M1 turrets. See this thread to know the difference between M1,M2, M3, and M5 turrets.
They do not match. Thus for the sake of this discussion, it my opinion the mil/mil or the M5 turrets are better utilized.

Dueling? I was putting that in because of the humor. You have brought up some great points to add to this discussion.


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: Skylar Mac] #3409725 07/25/12 08:00 PM
Joined: Mar 2009
Posts: 4,426
J
jeffbird Offline
Extreme Tracker
Offline
Extreme Tracker
J
Joined: Mar 2009
Posts: 4,426
Thanks for the series of very informative posts. Truly.
Have a good one. up



Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: jeffbird] #3412147 07/26/12 02:58 PM
Joined: Apr 2011
Posts: 3,594
S
Skylar Mac Offline OP
Extreme Tracker
OP Offline
Extreme Tracker
S
Joined: Apr 2011
Posts: 3,594
Jeff, thank you for contributing.


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: Skylar Mac] #3412363 07/26/12 04:24 PM
Joined: Sep 2009
Posts: 4,762
C
ccoker Offline
Extreme Tracker
Offline
Extreme Tracker
C
Joined: Sep 2009
Posts: 4,762
for long range use (500 to 1K) I definitely prefer mil/mil FFP scopes

why someone would put a turret system that doesn't match the reticle is beyond me..


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: ccoker] #3454262 08/08/12 02:35 PM
Joined: Apr 2011
Posts: 3,594
S
Skylar Mac Offline OP
Extreme Tracker
OP Offline
Extreme Tracker
S
Joined: Apr 2011
Posts: 3,594
Charles I think it is because here we are so use to standard measurments.

And someone who asked for a ranging reticle to be designed by the Germans, but when they recieved the prototype, mil/mil was foriegn or alien to them, and requested standard angular measurements be implemented.


Re: First Focal Plane or Second Focal Plane, What's the difference? [Re: Skylar Mac] #6782673 06/03/17 04:43 PM
Joined: Mar 2017
Posts: 61
R
Reydonpete Offline
Outdoorsman
Offline
Outdoorsman
R
Joined: Mar 2017
Posts: 61
Thanks for posting Skylar@SWFA , I'm glad you posted info in a way that explains how these items on scope work as well as how to choose and why when matching scope with ones intended use. Great explanation thanks for posing Good info

Previous Thread
Index
Next Thread

© 2004-2024 OUTDOOR SITES NETWORK all rights reserved USA and Worldwide
Powered by UBB.threads™ PHP Forum Software 7.7.3