Rifle Scopes FFP vs SFP performance

R

Red Belly

Sergeant
Full Member
Minuteman
Jul 28, 2009
301
13
MA
#1
I came across this on empire rifle's website discussing FFP & SFP reticles. It said:

<span style="font-style: italic">"Also, a reticle in the first plane transmits maximum light across the entire power range, whether set on 1.5X or on 6X. A scope with the reticle in second focal plane only transmits to the advertised twilight factor when set at the lowest setting."</span>

Just curious if this is true.
 
#2
Re: FFP vs SFP performance

I don't think that's true the biggest difference is how your reticle changes. For me an FFP scope is only good for range multiple target at a multitude of ranges at one time. Also the reticle is almost useless in some cases because it's so small at the lowest magnification. Hope that helps.
 
#3
Re: FFP vs SFP performance

You didn't answer his question. He was asking about differences in light transmission between scopes with FFP or SFP reticles, not about the utility of SFP versus FFP reticles.

I don't know the answer to his question, and it appears that you don't either.
 
#8
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Umm, sunglasses do not transmit light as much as clear lenses, or no lenses.
</div></div>

But sunglasses are specifically designed not to transmit.

Where a scope would seem to be specifically designed to gather, focus, and transmit.

Just going back to college physics (those refraction and reflection discussions.)
 
#10
Re: FFP vs SFP performance

Even clear polycarbonate lenses block 4~6% of light (94~96% transmission) due to a certain percent of photons reflecting off of the surface. In layman's terms they don't go anywhere, they just don't make it through.

I have no idea how that applies to FFP/SFP reticles though. That's a mystery.
 
#11
Re: FFP vs SFP performance

Once the light has entered the scope body and begins to travel down the series of glass.

My lay persons understanding (I am a Mechanical Engineer not a Optical Engineer) of the difference between FFP and SFP is where the reticle lies in those series of glass.
 
#12
Re: FFP vs SFP performance

Sure.

Your question sounded as if you thought that light going into a scope must of necessity come out the eyepiece. Perhaps I misunderstood what you were asking.

The following was written about telescopes used for astronomy, but applies as well to rifle scopes:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Lens elements lose light due to reflection from lens surface and absorption by the glass. Reflection from uncoated lens surface is ~4% for typical glasses and near-normal incidence. However, even simple anti-reflection coating, such as MgFl (magnesium fluoride), reduces reflectivity to ~1%, and more advanced coatings have it nearly eliminated. Unfortunately, nothing can be done about in-glass light absorption; it is at ~4% per inch of in-glass light travel for typical optical crown, and somewhat more for typical flint, averaged over the entire visual range (400nm-700nm). Losses due to in-glass absorption are roughly doubled in the blue/violet part of visible spectrum, compared to the green/red.

Light loss in glass elements, therefore, increases with the number of uncoated surfaces and the in-glass path length. For uncoated doublet objective, it is about 15% due to reflections, plus nearly 1% per inch of aperture due to in-glass absorption.
</div></div>
 
#13
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: modifier</div><div class="ubbcode-body">Even clear polycarbonate lenses block 4~6% of light (94~96% transmission) due to a certain percent of photons reflecting off of the surface. In layman's terms they don't go anywhere, they just don't make it through. </div></div>

I understannd the reflective nature of the material and that it will not transmit everything.

The point is the origional post stated a difference between a SFP and a FFP (both of which would have to travel the same path).

I am curious if the is a "mathematical" difference or a practical difference.
 
#14
Re: FFP vs SFP performance

If the reticle reflects X amount of light then the size of the reticle itself would matter just as much as the location within the tube. One would have to know the reticle location, area in mm^2, and magnification of each lens in front of the reticle.

One would think a larger reticle with thicker bars and subtension marks would block more light than one with two fine lines. Perhaps this has something to do with manufacturers' transmittance numbers.
 
#15
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: modifier</div><div class="ubbcode-body">If the reticle reflects X amount of light then the size of the reticle itself would matter just as much as the location within the tube. One would have to know the reticle location, area in mm^2, and magnification of each lens in front of the reticle.

One would think a larger reticle with thicker bars and subtension marks would block more light than one with two fine lines. Perhaps this has something to do with manufacturers' transmittance numbers. </div></div>

Again back to my question would be to take identical products with the exception of the FFP/SFP. For example a Nightforce NSX makes the same scope in FFP and SFP.
 
#16
Re: FFP vs SFP performance

It's more than likely a mathematical difference. I never took any optics-related physics courses though... only basic physics, hydrodynamics, and thermodynamics.
 
#18
Re: FFP vs SFP performance

Yes. From a mathematical standpoint one could say there's X amount of transmittance loss. From a practical standpoint you could hand someone two scopes, ask if they can see a difference, and enjoy the fact that they'll likely say "no."
laugh.gif


It's a difference between mental masturbation and reality. So, sarcasm aside, I'd say none of it really matters in the end.
 
#19
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: modifier</div><div class="ubbcode-body">Yes. From a mathematical standpoint one could say there's X amount of transmittance loss. From a practical standpoint you could hand someone two scopes, ask if they can see a difference, and enjoy the fact that they'll likely say "no."
laugh.gif


It's a difference between mental masturbation and reality. So, sarcasm aside, I'd say none of it really matters in the end. </div></div>

Reminds me of a joke about a mathmetician, a engineer, and a beautiful woman. That is for another time.
 
#21
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">
Again back to my question would be to take identical products with the exception of the FFP/SFP. For example a Nightforce NSX makes the same scope in FFP and SFP. </div></div>

I just asked Nightforce, and their response was:

1. They've never been asked this question before.

2. There is no difference in light transmission based on the location of the reticle. If both scopes have the same number of elements and coatings, the net light transmission will be the same, as long as there are no reducing apertures involved.
 
#23
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"> I just asked Nightforce, and their response was:

1. They've never been asked this question before.

2. There is no difference in light transmission based on the location of the reticle. If both scopes have the same number of elements and coatings, the net light transmission will be the same, as long as there are no reducing apertures involved. </div></div>

-That's kind of what I figured, but didn't know for a fact..........

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: modifier</div><div class="ubbcode-body">
It's a difference between mental masturbation and reality. So, sarcasm aside, I'd say none of it really matters in the end. </div></div>

That's what I firmly believe.


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I'm never going to own a scope with a SFP reticle, so the difference in light transmission is moot.
</div></div>

And that is the crux of the matter for me. I could give a rat's ass if a SFP scope (all other things being equal) transmitted light taht was a tiny percentage clearer or brighter than an FFP-I want to not miss a hold or lead because I didn't dial my power to just the right spot, period!
 
#24
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I'm never going to own a scope with a SFP reticle, so the difference in light transmission is moot.
</div></div>

And that is the crux of the matter for me. I could give a rat's ass if a SFP scope (all other things being equal) transmitted light taht was a tiny percentage clearer or brighter than an FFP-I want to not miss a hold or lead because I didn't dial my power to just the right spot, period! </div></div>

So why are so many manufacturers shipping variable-power mil-dot scopes with <span style="font-style: italic">only</span> SFP reticles? Is it purely the marginal cost or difficulty of building a FFP reticle? (And is that significant?) Is there no functional argument in favor of SFP mil-dots?
 
#25
Re: FFP vs SFP performance

The primary rationale for a FFP reticle is the ability to use the reticle graduations for holdovers, holdunders, wind holds, and moving target leads at any magnification. Serious tactical marksmen should not own any other kind of scope, IMO.

To people who are competition paper punchers, that rationale does not apply. They have the time to dial elevation and windage, so they don't care, and they like a reticle which does not change size, often with fine lines in the reticle, because they don't want the target obscured by the reticle. In addition, they shoot only during daylight hours, so they don't care about reticle visibility.

So, manufacturers offer choices to fit different market segments. It's a perfectly reasonable thing to do, if you're interested in maximizing market share.

I happen to fit only one of those market segments, although many people who shoot tactically fit in both.

Those manufacturers who offer only SFP reticles are apparently unconcerned about the tactical market. That's a valid choice.
 
#26
Re: FFP vs SFP performance

Are there any FFP mil-dot scopes on the market significantly below $1000?

I haven't been able to find any, though there are a plethora of SFP mil-dots with the same specs at every price point down to $100.
 
#27
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">Are there any FFP mil-dot scopes on the market significantly below $1000?

I haven't been able to find any, though there are a plethora of SFP mil-dots with the same specs at every price point down to $100. </div></div>

SWFA Super Sniper 3-9x42 FFP mil/mil- $600ish

Bushnell 4200 3-12x44 FFP Mil/Mil- $640ish
 
#28
Re: FFP vs SFP performance

FYI: I noticed that Vortex has planned to list its FFP PST at $150 more than their equivalent SFP. I asked them about this and Scott said, "Yes, the FFP is quite a bit more difficult and expensive to manufacture."
 
#29
Re: FFP vs SFP performance

FFP scopes are great for hunting apps, esp if you are shooting multiple targets at multiple ranges relatively quickly.

In a prairie dog town, targets can be 100 yards out to as far as you want to shoot. Using the reticle for holdover works fine for this until mirage kicks up and scope power is dialed down to compensate. Now, at lower power, the holdover points are not what they were and I start missing which pizzes me off. I much prefer the red mist than a cloud of dust.

Of course, range readings could be taken and the scope dialed for a hit with a SFP scope.

A FFP scope would be a big benefit in this situation. I plan on getting a Vortex PST (or 3) when they become available.
 
#30
Re: FFP vs SFP performance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">FYI: I noticed that Vortex has planned to list its FFP PST at $150 more than their equivalent SFP. I asked them about this and Scott said, "Yes, the FFP is quite a bit more difficult and expensive to manufacture." </div></div> What I really should have said was difficult and expesive to design. When you have a SFP reticle this leaves you with the whole length of the scope,first and second focal plane, to optimze your optical design. With a FFP you have to do all of that in just the FFP portion of the optic. Obviously this is the short story ,but I think it says what it needs to. Let me know if you have any further questions that I may be able to help with.


Best Regards
Scott
 
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