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first or second focal plane |
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chance
Optics GrassHopper Joined: November/03/2007 Status: Offline Points: 6 |
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Posted: December/19/2007 at 18:52 |
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I asked your opinion on a rifle scope before, and I thank you for your information. Now I have another question. What is the difference between first focal plane and a second focal plane, scope? I hunt range of 75 to 150 yards, in heavily wooded areas. I sometimes take quick shots. Will you please tell me which option will be best for me and why you think so?
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RONK
Optics Master Extraordinaire Joined: April/05/2007 Location: United States Status: Offline Points: 3199 |
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Somebody else can probably explain it better than I can, but in practical terms, all fixed power scopes are FFP.
Variables are available in both FFP and SFP, depending on the manufacturer. Some manufacturers produce models in both types.
The essential difference between them is that in a FFP scope, the reticle and the target both grow in apparent size within the field of view as you increase magnification, the reticle remaining the same in relation to the image of the target. For example, in a variable tactical scope of FFP, the distance between two mil-dots, center to center, will always be 3.6 inches at one hundred yards, regardless of the magnification setting. In a SFP scope it will vary depending on the setting, subtending 3.6 inches at 100 yards (1 milliradian) at only one of the magnification settings,(usually 10x or 12x, but this also varies according to the designed role of the scope and the manufacturer's whim.)
In a hunting scope, the Europeans have traditionally favored FFP scopes because they often hunt in near darkness, and like to crank up the magnification, which makes the reticle appear big and prominant against the animal. The downside is that it also causes the reticle to cover too much of the animal when turned up for long-range hunting of tiny varmints.
In your situation, I would recommend a high-quality, fairly low-power variable, perhaps 1-4x or a fixed 4x. Just make sure to get a fairly stout reticle and I don't think it will matter too much in your situation whether it's SFP or FFP if you choose a variable.
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Urimaginaryfrnd
MODERATOR Resident Redneck Joined: June/20/2005 Location: Iowa Status: Offline Points: 14964 |
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At 75 to 150 yds most cartridges are relatively flat as far as trajectory check to see what the trajectory is of your particular cartridge. Were a FFP becomes useful is farther out using a reticle that has multiple marks like mil dot or MP8 or TMR. With FFP the hold over is always the same but with a fixed power the hold over is always the same also. For the distances mentioned I would use a 4x or a 6x if I chose a fixed and I really think that you might do well to look at Trijicon Accupoint scopes or an Aimpoint with a 2moa dot. There are some great buys on SAMPLELIST on used and demo models. Kahles scopes are well thought of and a low variable with the 4a reticle might be a great choice for you. So other factors are far more important at those distances than FFP or SFP.
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"Always do the right thing, just because it is the right thing to do". Bobby Paul Doherty Texas Ranger |
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RifleDude
MODERATOR EVIL OPPRESSOR Joined: October/13/2006 Location: Texas Status: Offline Points: 16337 |
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This topic and the pros and cons of each have been covered several times, so if you do a search, you should find plenty of information about the relative merits of both. The reason the FFP reticle gets larger at same ratio as the target image when magnification is increased is because it is located on the objective side of the scope in front of the zoom tube, so it is being magnified along with the target. It always subtends the same amount of the target regardless of magnification. A SFP reticle, on the other hand, is located in the eyepiece end of the scope, in front of the zoom tube, so it remains the same apparent size at all magnifications, thereby subtending less of the target at higher magnification.
I personally prefer FFP for low light hunting and big game, and I prefer SFP for varmint, small game, and target shooting.
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Ted
Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle. |
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cyborg
Optics God Gaseous Clay Joined: August/24/2007 Location: North Georgia Status: Offline Points: 12288 |
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The relative placement of the reticle is what describes the FFP or the SFP. The front or FFP is in the first focal pane which is to say nearer the objective lens in front of the erector. The second focal plane is nearer the ocular, behind the erector. Thus in a variable power scope a FFP will zoom in the same proportion that the sight picture does, as it is a part of the sight picture. The SFP will not do this.
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An armed public are citizens. A disarmed public are subjects. OATH KEEPER #8233 Support us, and join our cause. Cyborg |
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Urimaginaryfrnd
MODERATOR Resident Redneck Joined: June/20/2005 Location: Iowa Status: Offline Points: 14964 |
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Which brings us back to my point that FFP vs SFP is a moot point at 75 to 150 yds because trajectory is relatively flat at those distances.
( [moot] - of little or no practical value or meaning; purely academic. )
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"Always do the right thing, just because it is the right thing to do". Bobby Paul Doherty Texas Ranger |
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cyborg
Optics God Gaseous Clay Joined: August/24/2007 Location: North Georgia Status: Offline Points: 12288 |
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You're exactly right Urimaginary, I figured I'd answer what might be his next question.
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With Freedom comes great responsibility, you cannot have one without the other
An armed public are citizens. A disarmed public are subjects. OATH KEEPER #8233 Support us, and join our cause. Cyborg |
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tahqua
MODERATOR Have You Driven A Ford Lately? Joined: March/27/2006 Location: Michigan, USA Status: Offline Points: 9042 |
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Good summary and true for myself.
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RONK
Optics Master Extraordinaire Joined: April/05/2007 Location: United States Status: Offline Points: 3199 |
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Well, it's a moot point only if he intends to use reticle subtension to determine range, which I doubt, by his original post. The issue of a reticle's apparent size as it pertains to its' visibility will still be a factor for him in low light, at least to some extent. I used the mil dot subtension scenario earlier merely to illustrate the properties of FFP vs. SFP systems.
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RONK
Optics Master Extraordinaire Joined: April/05/2007 Location: United States Status: Offline Points: 3199 |
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+2
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