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Focal plane and reticle.

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wolfee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wolfee Quote  Post ReplyReply Direct Link To This Post Topic: Focal plane and reticle.
    Posted: May/03/2012 at 09:47
I see some scopes say the reticle is mounted in the front focal plane and some say in the second focal plane.  For all I know there is 7 other focal planes you can stick the reticle in.  Anyway.  What's the difference?  Does it matter? 
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brodeur272 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote brodeur272 Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2012 at 10:36
First focal plane reticles (FFP) become larger when you turn up the magnification.  They can be used for ranging on game as the dimensions between the posts stay the same.  On second focal plane reticles (SFP), the reticle stays the same, but the subtensions (thicknesses) change. 
 
The difference, I've found depends on you the shooter.  I have both and prefer the FFP for most applications.
 
 
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wolfee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wolfee Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2012 at 15:19
Thanks. 
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Skylar McMahon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Skylar McMahon Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2012 at 16:29
Brodeur did a good job explaining this.
Reticles in modern variable powered rifle scopes are installed in 2 different ways. Scopes with FFP reticles are becoming more popular for tactical and long range shooters as they require the values of the reticle to be constant throughout the variable power range. FFP scopes are more expensive due to costly and time consuming design and production. Scopes with SFP reticles remain popular with target shooters and other shooters who wish the reticle to remain the same size throughout the variable power range. The reticle does not clutter the image at maximum power settings.
 
FFP (First Focal Plane) scope
First focal plane scopes have the reticle installed towards the front of the erector tube or forward of the magnification lenses. The reticle is very near the centre of the turret housing. When the magnification is increased the reticle increases in size along with the image you are looking at.


SFP (Second Focal Plane) scope
Second focal plane scopes have the reticle installed towards the rear of the erector tube or rearward of the magnification lenses. The reticle is fixed near the ocular or eye piece.

When the magnification of the scope is increased the image size increases, however the reticle size remains the same. The value of the reticle subtensions now change. If the value of the subtensions are set to "True" Milliradian value at 10x, then when the power is increased to 20x the value of the Milliradians has now halved. Each scope manufacturer will explain in the user manual their "True" Milliradian power setting. i.e. Nightforce NXS always have theirs at maximum power.

Advantages of FFP Rifle Scopes

1. The value of the reticle always stays the same through the power range. The constant value of the reticle allows the shooter to;

a. Calculate the range to the target

b. Maintain the match between the reticle value and the turret value (Milrad turret and Milrad reticle)

2. Calculate the size of objects or targets knowing the values of the reticle and range to the target.

Advantages of SFP Rifle Scopes

1. As the reticle stays the same width with an increase in image size, this reticle will not clutter the target when on very high powers.

2. SFP plane rifle scopes are usually cheaper for the same make.

FFP scopes are advantageous for shooters who fall into the following category;

Long Range Hunters

Tactical Shooters

Snipers

Multi Distance shooting with spotters

Any other shooter who requires a measured reticle pattern

SFP scopes are advantageous for shooters who fall into the these categories;

Target Shooters (Benchrest and F Class)

Shooters who prefer to use the scope to observe bullet holes in the target

Shooters who prefer plain style reticles

This link here is also full of very valuable information.


 

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Sparky View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sparky Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2012 at 22:16
Originally posted by Skylar McMahon Skylar McMahon wrote:

i.e. Nightforce NXS always have theirs at maximum power.


Actually on at least some of the Nightforce reticles they provide the sub tension values at low power and mid power as well.
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