Part 1 : Merits and Demerits of FFP, SFP and Dual reticles – The reason March chose a Dual tree reticle over a FFP reticle for 1-10×24 Shorty FFP scope
After DEON (manufacturer of March Scopes) launched the 1-10×24 Shorty FFP scope, we received many inquiries to make a tree reticle for this scope. We put a lot of thought into this discussing with our customers and dealers. The most difficult decision for us was whether to design the tree reticle in FFP or in dual reticle (combination of FFP and SFP). The technical and assembly challenges with respect to dual reticles are extreme and the tolerances required in assembly of dual reticles is such that very few manufacturers are able to do it, especially with a 10X zoom ratio. However we wanted to combine merits of both FFP and SFP reticles to benefit shooters and this is the reason for our decision.
We will explain Part 1 to 3 in each article. You can click the headlines below in blue and jump to the section you are interested.
(Part 1) Characteristics of reticles
The point of aim (POA) does not change throughout the entire zoom range. This is because the image formed on the first plane and the first focal plane reticle are both placed in front of the zooming feature (erector lens), and as they zoom in and out together completely matching, POA shift does not occur. The scale value will always be consistent regardless of the magnification and easy to calculate.
For FFP reticle, when you change the magnification, the target and the reticle will zoom in and out collectively. The reticle lines and dots will be fine at lower magnification and thicker at higher magnification.
The size and thickness of the SFP reticle is always constant and only the target image will be larger at higher magnification. As the reticle lines and dots will not be thicker at higher magnification, you can achieve a clear uncluttered view even at higher magnification. At the same time, you have a thick and easy to see reticle even at the lowest magnification.
Scale value of the reticle is designed at the specific magnification. This means that you will need to convert the scale value at other magnification. However, the most important thing to note is that the point of aim (POA) will change more or less throughout the entire zoom range since the second focal plane reticle is assembled after the zooming feature (erector lens). The image formed on the first focal plane reticle will zoom in and out through an erector lens. On the other hand, the SFP reticle is placed in a fixed position after the erector lens not being affected by it. As the image and the SFP reticle does not 100% overlap, POA shift to some degree is unavoidable. This is the nature of the SFP reticle for all scopes which exist in the world.
For March Scopes, we comply with and try to excel the ISO specification 14135-2:2017 (tolerance for image displacement due to zooming) as much as possible. We pride ourselves in making the POA shift as minimal as can be, assembly accuracy being our strong suit. However no matter how much we can minimize the POA shift, it can’t be zero for any scopes as this is simply the principle of optics.
Merit of a SFP reticle : The size and thickness of reticle line and dot is always constant.
→ Cross line and daybright center dot is in SFP reticle. This means that at higher power, the center dot will not bloat and hinder the view. On the other hand, the reticle lines and the center dot will not be too fine at lower power as in the FFP reticle. Cross line and the center dot in the dual reticle is usable throughout the entire magnification range as they are in SFP reticle. Also this dual reticle (DR-1 and DR-TR1) has the brightest center fiber dot (FD-1) among all our FFP scopes, which can be fully usable for daytime as well.
Merit of a FFP reticle : The scale value will always be consistent and it is easy to calculate.
→ Scale is in FFP reticle. You do not need to convert the scale value at other magnification.
Demerit of a SFP reticle : When you are shooting just with the SFP reticle, though there is a POA shift you do not realize its existence as there is nothing to compare with. In a dual reticle, as the FFP reticle with no POA shift is behind the SFP reticle which has a POA shift due to the nature of optics, discrepancy between the two reticles is unfortunately not 0.0%.
This is why the technical and assembly challenges with respect to dual reticles are extreme as the highest level of aligning the FFP and SFP reticles is essential. The tolerances required in assembly of dual reticle is such that very few are able to do it, especially with a 10X zoom ratio. Any deviation from these extremely tight tolerances will be visible in the 10X zoom range. But please be assured that the assembly of this scope, like all our other offerings, is meticulous. We are pushing the limits of the state of the art in reticle design. This is what we are known for: superb assembly of extremely strong fine works of art.
In order to combine merits of both FFP and SFP reticles to benefit shooters, we decided to make a dual reticle for 1-10×24 Shorty scope. However each reticle has different characteristics so please choose according to your preference.
You can click the headlines below in blue and jump to the section you are interested.
Written by : Mari Morita