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Rifle Scopes Why do you think an adjustable parallax feature is needed on LPVOs? ? ?
- Thread starter Terry Cross
- Start date
50mm is not a 1x lens. There is no such thing as a 1x lens unless we start talking about macro photography which is a different field altogether..
This will come off slightly offensive, so my apologies in advance. I simply do not have a better way of saying this.
Historically, people behind the photographic naming conventions were artists, not scientists. That, by itself would not have been a problem, except a bunch of them were technically illiterate pompous blowhards and they are responsible for some of the more idiotic camera terms we have.
50mm lens on a full frame camera is often referred to as a "normal lens" because it has roughly similar perspective to how we see with the naked eye, but that has very little to do with FOV. FOV of a human eye is hugely wider.
With all that, FOV and magnification of an afocal optic like a riflescope is defined quite differently. I really need to re-record these with the better microphones I now have.
ILya
Denys knows what he is talking about. I consider him a friend, so he ends up being on the pointy end of my nerdy jokes here and there.
We do often disagree on terminology though.
ILya
Thanks, Terry. This is generally a topic that needs to be covered in more detail. I started doing these livecasts a couple of times a month. Maybe I should dedicated a couple of them to going over the internal workings of a riflescope and to how all these performance parameters jive together.
ILya
Check your email. I'm afraid you might have received a "ponfo mirann" response from the Vulcans. They do not have any sense of humor.
The 50-55 mm lens is a 1x lens; there is no magnification in that lens. If you wanted to impress your girlfriend with your photographic skills and make her look great, you would use a mild telephoto like an 85 or 100mm lens, not the normal 50mm lens that usually came with the SLR body. The macro lens is more of a 1:1 lens.
It's all a question of perspective.
Like rumble strips on the interstate........
Rifle Scopes!
Specifically LPVO Rifle Scopes.
Really, really specifically the need for Parallax Adjustment on LPVO Scopes.
That is what this thread is about.
Quit drifting too far out of the lane.
./
Rifle Scopes!
Specifically LPVO Rifle Scopes.
Really, really specifically the need for Parallax Adjustment on LPVO Scopes.
That is what this thread is about.
Quit drifting too far out of the lane.
./
That is patently untrue. The term "1x" has a very specific definition and lens focal length is not it. "1:1" for a macro lens is the exact definition of 1x for a photographic lens. For far field lenses, the term "magnification" carries no meaning.
ILya
I didn't read everything in this thread and some of the posts look to be beyond my depth anyway but...
What is the downside to just having a fixed parallax on a LPVO at say 250-300 with no adjustment? Why is everything fixed at 100?
What is the downside to just having a fixed parallax on a LPVO at say 250-300 with no adjustment? Why is everything fixed at 100?
The downside is that all the good folks out there who buy fancy LPVOs and only shoot at 100yards off the bench will complain that the target is not perfectly sharp on 10x.
ILya
Is there any technical issue with zero process if parallax is set that far out
(ie, fixed @ 200-300yd etc)?
If it's set to 300, a 100m target is likely to be a little blurry, and it might be harder to aim small. Additionally, you'll experience some potential for parallax error (i think enough to care), but that can be mitigated if you keep good/consistent head position.
Thanks, that's was kind of my thoughts as well, that it would be more of a marketing headache than a shooting issue.
I mostly wondered what the affect was on clarity/resolution of seeing fine details of a target in the 75-100 range if the weapon was to be used as a department duty weapon. Really just trying to find downsides...
Guess it depends on the department weapon. If it’s my local department, I want them dudes using a spotting scope or big eyes, maybe followed up secondary with a weapons sight that is at least 20x, THEN go to some lower power shit and all three have to agree. Don’t want any mistakes if it’s my cranium about to be mistakenly canoe’d.
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I just dial down the magnification a little bit for closer distances and it works fine.
I would imagine that for department/duty use, distances beyond 600 yards are not critical, so typical 125/150 yard focus setting is fine.
ILya
That depends on how the scope is constructed and on the magnification. In practical terms, with a scope like the Razor Gen3 1-10x24 with the way it is set up from the factory, I would be pretty comfortably on a coyote size target out to 800 yards or so. Maybe a little more, but that also really depends on lighting conditions, etc.
ILya
Around here we can have coyote, domestic canine, and wolf in same habitat...
typically the rules of engagement for each would be pretty differnt under the law
Around here if it messes with my livestock it dies. Only things that are off limits are Louisiana Black Bears and the Pine Snake.
What about Nightforce ATACR 1-8, Kahles 18i 1-8, or the Steiner M8xi 1-8?? Those are kind of around the area I am looking?
Thank you
I’m not ILya... by a long shot. But I have experience with pretty much every high end LPVO. I’d echo similar range capabilities with the ATACR and Kahles, though I find the ATACR reticle preferable for longer shots.
Even at 800, if I miss a coyote it was me, my gun’s accuracy limitations, or wind, not the scope.
Even at 800, if I miss a coyote it was me, my gun’s accuracy limitations, or wind, not the scope.
Thank you! That's really what I needed to know. I am going to get up to see Terry one of these days to look through an ATACR just to confirm.
I’m a Nightforce lover but I’d advise you to look through the ATACR if you have a chance before buying. I found the tunneling a little off putting, but the scope performed wonderfully beyond that.
This is exactly what I was thinking. I guess I should have read through it all before commenting previously.
It's good to know they will do that. How did you arrive at the decision to make it parallax free at 300 yds?
And to answer the main question of the thread, I personally don't think and adjustable parallax is needed on a LVPO, only that the parallax free distance be revised to optimize the scopes intended use. I would guess that everyone has a different idea of what that is, hence the arguments for and against.
I feel like the capped/uncapped path is the way, everyone's eyes are different so being able dial to one's default preference or click-click dial off a bench sometimes sounds nice.
That said, I don't think I've ever owned an LPVO with adjustable parallax, because if I had, I must not miss it, because I can't remember ever using it or particularly caring about it. (I still run a Steiner p4xi 1-4 though, I haven't gotten a chance to look through the newer 1-10 Razors or top-tier NF, it probably matters more there.)
That said, I don't think I've ever owned an LPVO with adjustable parallax, because if I had, I must not miss it, because I can't remember ever using it or particularly caring about it. (I still run a Steiner p4xi 1-4 though, I haven't gotten a chance to look through the newer 1-10 Razors or top-tier NF, it probably matters more there.)
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If there are many arguments for/against where to fix the parallax, quite frankly that sounds like adjustable parallax (maybe capped?) would be ideal.
But ideal doesn't mean feasible (with budget included as a factor in feasibility).
If everyone has a different idea of what it is, that pretty means you are advocating for adjustable lockable side focus.
I calculated that ~280-300yard objective focus will give me better mid/long range performance without sacrificing the short range too much.
ILya
They are good LPVOs. Kahles and Steiner are SFP, so it is not really apples-to-apples, but both work quite nicely from what I have seen.
ATACR is more of a direct comparison, being FFP. It is a very competent design, but FOV is a bit on the narrow side.
ILya
How important is that for LPVO? I'm debating that in my head, just like parallax. Is it super critical? Thinking out loud.
I currently have a Leupold Mark4 1.5-5 M/RT that I had used in Iraq. Very effective optic and I really like it. There are some things I think it could do better but it worked for me and it was what I had for that deployment (still have it since I bought it).
As is often the case, if you have something and use it, you will get competent with it.
The whole reason behind modern LPVOs is to have good 1x performance. For speed, it does make a difference. If wider FOV options were not there, I'd use whatever is available and be happy. If I am starting from scratch, I'll go with whatever is the best available option within my budget. FOV is a part of that consideration.
ILya
Very true! But, we have options now and navigating all of those options can sometimes be a challenge. Some of us suffer from paralysis by analysis and a little bit of expert assistance just helps to give us that push.
Well those words, in particular, would be a great post in MANY threads around here !!
I have a range of quality in my inventory ... NV and Thermal, etc. across most elements of gear. I purposely go out with the lower quality elements often to avoid "training scars" of only using "the best". Adjusting procedures to account for varying levels of quality seems like good practice.
I've sort of kept up with this thread for a fee weeks and it really has me thinking we're sucking this egg too hard. I use the Razor 1-6x and ATACR 1-8x as examples having months or years behind one, don't care about any others, and will say you have two choices depending on your needs: focus your ocular at 1x until all optical shift disappears if you shoot close and fast and focus at high end if you are primarily shooting at mid range. You have to chose one or the other based on your needs because there is a qualitative and quantitative difference. The discrimination argument is a farce: I absolutely do not need side focus/parallax to PID with a LPVO. What isn't arguable is how fast and accurate I am depending on how I set the optic up. I could do everything I do from work to comps with either a 1-8x or a 7-35x with no need for anything in between. One needs adjustable parallax and one doesn't.
The hyperfocal distance is the distance at which you focus a lens to obtain the greatest depth of field (DOF). Viewed another way, the hyperfocal distance is the minimum distance at which the objects at infinity are acceptably sharp.
The formula for calculating the hyperfocal distance of a lens is:
H = L x L / F / CoC / 1000, where:
H is hyperfocal distance in meters.
L is the focal length of the lens.
F is the F-Number of the lens.
CoC is the diameter of the Circle of Confusion in mm.
As I had explained earlier, riflescope makers do not divulge the focal length of their riflescopes; some consider it a trade secret as part of their design. Without the focal length, we cannot use the formula.
However, we can guestimate the focal length and work from there. For this, you will need a ruler or a caliper that measure in metric or just convert the measurements to metric. As I said, you will need a ruler or caliper, a pencil, paper, eraser, rubber band, fork and a beer.
A riflescope is essentially three parts: the objective lens group, the erector assembly, and the eyepiece. The magnification range of a riflescope is calculated by dividing the focal length of the objective group by the focal length of the eyepiece and then multiplying by the zoom ratio of the erector set.
The focal length of the objective lens is the distance between the objective lens group and the first focal plane, regardless if the scope is FFP or SFP. I believe that FFP is usually located in the middle of the elevation knob, where there is the greatest range of movement for the FFP. Again, that’s irrespective of FFP or SFP design.
Now if you look at the objective lens from the front, you can see that sometimes it’s close to the front edge and sometimes is further in. There are more than one lens in that objective lens group. This makes it difficult to find out exactly where to measure from, but I would think that where the objective starts to taper towards main tube size is near the lenses. I can’t imagine that there would be a big gap between the back of the lenses and the start of the taper. So I measure about a half inch forward of where the taper starts to the middle of the elevation dial. You also need to do measure parallel to the riflescope body.
1- place the rubber band tightly around the wrist of the hand holding the riflescope.
2- Pick up the riflescope and identify the objective part of the scope. That’s usually the big end of the riflescope, but on LPVOs that will be the small end of the riflescope.
3- In your other hand take the measuring instrument and place one end on the objective part about a half inch in front of the start of the taper. On an LPVO, you have to be a little imaginative; just remember that the diameter of the lens is small and so is the thickness, but there are a couple of lenses in the objective group.
4- Measure the straight distance to the middle of the elevation knob.
5- Record that measurement on the paper using the pencil.
6- Measure it is again and mark down the second reading below the first one.
7- Compare the two measurements.
The Circle of Confusion (CoC) is going to be a number of your choosing. To my mind, this number would vary between .03mm and .01mm. The larger the number, the less picky you are about what looks in acceptable focus. I think it should vary with the magnification that you want to use. So, let’s say your zoom ratio is 10X, like in that March 1-10X24 discussed in this thread. I would say that if I am going to stay between 1-3X, I would choose a CoC of .03mm. If I’m going to go up to 7X, I would choose a CoC of .02mm. If I want the whole 1-10X without having to touch the side focus, I would choose a CoC of .01mm. This is something that you will have to decide for your needs.
Now plug in the three numbers that we have identified into the formula and we are ready to calculate the hyperfocal distance for that riflescope.
So let’s say the focal length is 48mm and the diameter of the lens is 24mm, the F-number of the lens is 48/24=2.
H= (48 * 48) / 2 / .03 / 1000 H= 38.4 meters
H= (48 * 48) / 2 / .02 / 1000 H= 57.6 meters.
H= (48 * 48) / 2 / .01 / 1000 H= 115.2 meters.
Of course, you can reduce this further by doing: (48*48)/2/1000 and then divide the result (1.152) by whatever CoC you want. That number (1.152) only applies to the riflescope that you measured to get the numbers.
But that number is sterile, it only tells us at which distance everything behind it will be in focus. What about in front of that distance?
I will give you the numbers for each and then we will explore how that’s done and how to take it further.
At H = 38.4, CoC = 0.03, the near limit is 19.2 meters.
At H = 57.6, CoC = 0.02, the near limit is 28.8 meters.
At H = 115.2, CoC = 0.01, the near limit is 57.6 meters.
Now, let me introduce you to the DOF Master calculator. This is the site I use to calculate DOF coverage and other such things.
Online Depth of Field Calculator (dofmaster.com)
It requires 4 pieces of data to calculate and produce great information.
The first one is Camera, film format, or circle of confusion. For our purposes, we use CoC. So drop down the list and go to the end to find the CoC values. Be careful with the decimal point. We are looking at values between 0.010mm and 0.030mm. As I explained earlier, the bigger the CoC, the larger the DOF.
The second number is the Focal length. This is the value we (painfully) measured on the riflescope earlier. The numbers are a little wonky, but remember this is a camera site.
The third number is the Selected f-stop (or f-number). Again, the numbers may be a little wonky, just select the one that is closest to your calculated one.
The fourth and final number is the Subject distance and its associated unit of measure.
So let’s say I would like to know where to focus my riflescope to have an acceptable DOF from say 20 meters to 200 meters at up to 7X. For that, I select a CoC of 0.020. Next. I select the hyperfocus distance of 57.6 meters to see what this produces. I get a near limit of 29m and, of course, infinity. Remember, this is the hypefocal distance. That quite close to what I’m looking for. Let’s bring it down to 40 meters. Remember, the near limit DOF is much shallower than the far limit. At 45, I get a near limit of 25 and a far limit of 205 meters. That’s pretty good. I can tweak it a little further towards the near limit but every meter I subtracts I lose s significant chunk at the other end and the near limit crawls.
This is where you start making your own decisions and figure out what is “acceptable sharpness” for you and what distances and magnifications are right for you. This is where the riflescopes with the side focus provide you with the flexibility to customize them for your needs if you so desire.
Of course, if your riflescope does not have a side focus, the DOF Master will show you what the DOF parameters are and you can certainly play with the CoC values to go along with the magnification.
This is all meant as a guide, and to help understand how to use a side focus. The focal length numbers I used above are approximations only.
The formula for calculating the hyperfocal distance of a lens is:
H = L x L / F / CoC / 1000, where:
H is hyperfocal distance in meters.
L is the focal length of the lens.
F is the F-Number of the lens.
CoC is the diameter of the Circle of Confusion in mm.
As I had explained earlier, riflescope makers do not divulge the focal length of their riflescopes; some consider it a trade secret as part of their design. Without the focal length, we cannot use the formula.
However, we can guestimate the focal length and work from there. For this, you will need a ruler or a caliper that measure in metric or just convert the measurements to metric. As I said, you will need a ruler or caliper, a pencil, paper, eraser, rubber band, fork and a beer.
A riflescope is essentially three parts: the objective lens group, the erector assembly, and the eyepiece. The magnification range of a riflescope is calculated by dividing the focal length of the objective group by the focal length of the eyepiece and then multiplying by the zoom ratio of the erector set.
The focal length of the objective lens is the distance between the objective lens group and the first focal plane, regardless if the scope is FFP or SFP. I believe that FFP is usually located in the middle of the elevation knob, where there is the greatest range of movement for the FFP. Again, that’s irrespective of FFP or SFP design.
Now if you look at the objective lens from the front, you can see that sometimes it’s close to the front edge and sometimes is further in. There are more than one lens in that objective lens group. This makes it difficult to find out exactly where to measure from, but I would think that where the objective starts to taper towards main tube size is near the lenses. I can’t imagine that there would be a big gap between the back of the lenses and the start of the taper. So I measure about a half inch forward of where the taper starts to the middle of the elevation dial. You also need to do measure parallel to the riflescope body.
1- place the rubber band tightly around the wrist of the hand holding the riflescope.
2- Pick up the riflescope and identify the objective part of the scope. That’s usually the big end of the riflescope, but on LPVOs that will be the small end of the riflescope.
3- In your other hand take the measuring instrument and place one end on the objective part about a half inch in front of the start of the taper. On an LPVO, you have to be a little imaginative; just remember that the diameter of the lens is small and so is the thickness, but there are a couple of lenses in the objective group.
4- Measure the straight distance to the middle of the elevation knob.
5- Record that measurement on the paper using the pencil.
6- Measure it is again and mark down the second reading below the first one.
7- Compare the two measurements.
- If the measurements are substantially different place the riflescope down on the table, pick up the fork and stab the hand that held the riflescope. Use the eraser to get rid of your mistake, then go back to step 3.
- If the measurement are essentially the same, add them up and divide by two. Then drink the beer to celebrate. You can remove the rubber bad from your wrist.
The Circle of Confusion (CoC) is going to be a number of your choosing. To my mind, this number would vary between .03mm and .01mm. The larger the number, the less picky you are about what looks in acceptable focus. I think it should vary with the magnification that you want to use. So, let’s say your zoom ratio is 10X, like in that March 1-10X24 discussed in this thread. I would say that if I am going to stay between 1-3X, I would choose a CoC of .03mm. If I’m going to go up to 7X, I would choose a CoC of .02mm. If I want the whole 1-10X without having to touch the side focus, I would choose a CoC of .01mm. This is something that you will have to decide for your needs.
Now plug in the three numbers that we have identified into the formula and we are ready to calculate the hyperfocal distance for that riflescope.
So let’s say the focal length is 48mm and the diameter of the lens is 24mm, the F-number of the lens is 48/24=2.
H= (48 * 48) / 2 / .03 / 1000 H= 38.4 meters
H= (48 * 48) / 2 / .02 / 1000 H= 57.6 meters.
H= (48 * 48) / 2 / .01 / 1000 H= 115.2 meters.
Of course, you can reduce this further by doing: (48*48)/2/1000 and then divide the result (1.152) by whatever CoC you want. That number (1.152) only applies to the riflescope that you measured to get the numbers.
But that number is sterile, it only tells us at which distance everything behind it will be in focus. What about in front of that distance?
I will give you the numbers for each and then we will explore how that’s done and how to take it further.
At H = 38.4, CoC = 0.03, the near limit is 19.2 meters.
At H = 57.6, CoC = 0.02, the near limit is 28.8 meters.
At H = 115.2, CoC = 0.01, the near limit is 57.6 meters.
Now, let me introduce you to the DOF Master calculator. This is the site I use to calculate DOF coverage and other such things.
Online Depth of Field Calculator (dofmaster.com)
It requires 4 pieces of data to calculate and produce great information.
The first one is Camera, film format, or circle of confusion. For our purposes, we use CoC. So drop down the list and go to the end to find the CoC values. Be careful with the decimal point. We are looking at values between 0.010mm and 0.030mm. As I explained earlier, the bigger the CoC, the larger the DOF.
The second number is the Focal length. This is the value we (painfully) measured on the riflescope earlier. The numbers are a little wonky, but remember this is a camera site.
The third number is the Selected f-stop (or f-number). Again, the numbers may be a little wonky, just select the one that is closest to your calculated one.
The fourth and final number is the Subject distance and its associated unit of measure.
So let’s say I would like to know where to focus my riflescope to have an acceptable DOF from say 20 meters to 200 meters at up to 7X. For that, I select a CoC of 0.020. Next. I select the hyperfocus distance of 57.6 meters to see what this produces. I get a near limit of 29m and, of course, infinity. Remember, this is the hypefocal distance. That quite close to what I’m looking for. Let’s bring it down to 40 meters. Remember, the near limit DOF is much shallower than the far limit. At 45, I get a near limit of 25 and a far limit of 205 meters. That’s pretty good. I can tweak it a little further towards the near limit but every meter I subtracts I lose s significant chunk at the other end and the near limit crawls.
This is where you start making your own decisions and figure out what is “acceptable sharpness” for you and what distances and magnifications are right for you. This is where the riflescopes with the side focus provide you with the flexibility to customize them for your needs if you so desire.
Of course, if your riflescope does not have a side focus, the DOF Master will show you what the DOF parameters are and you can certainly play with the CoC values to go along with the magnification.
This is all meant as a guide, and to help understand how to use a side focus. The focal length numbers I used above are approximations only.
I said I was going to do it and I try to keep my promises. It took a while, but it's here.
So I bounced on over from a Leupold 2-10x30mm thread.
I have read a lot of theories and preferences here. But I watch a lot of 9 Hole reviews in which Henry shoots stuff with LPVO’s and iron sights from 100-1000-ish yds with no problem. Granted, not paper targets.
So, without side focus, has anyone really noticed that they can’t hit the spot where they want to hit?
Not theory, not “I’ll bet…”, not, “I like…” or, “Someone told me…”
More like, “I missed or scored X, I then switched to an LPVO scope w/side focus that day and then I hit or scored Y.”
Being civil here; I’m curious.
I have read a lot of theories and preferences here. But I watch a lot of 9 Hole reviews in which Henry shoots stuff with LPVO’s and iron sights from 100-1000-ish yds with no problem. Granted, not paper targets.
So, without side focus, has anyone really noticed that they can’t hit the spot where they want to hit?
Not theory, not “I’ll bet…”, not, “I like…” or, “Someone told me…”
More like, “I missed or scored X, I then switched to an LPVO scope w/side focus that day and then I hit or scored Y.”
Being civil here; I’m curious.
It’s an old thread, but someone else revived it… Why do we want parallax on an LPVO? On a 1-10x most of us shot well beyond 100 yards.
While I'm not PRS/competition guru or youtube influencer, I saved up the coin to go from a little 1.5x S&B fixed power to the spankin' new Schmidt & Bender 1.1-4x20 Short in the early/mid 2000's and have never stopped. Without hyperbole, I'm willing to bet I've had as much hands-on and field time a Non industry insider can get on this class of optic. This includes every flavor of S&B, NF, Kahles, Vortex Razor, Leupold CQBSS, and some others and sometimes multiple specimens of the above in different reticles. Most get used on some sort of 14.5-18" AR15 SPR/DMR but have seen use on compact bolt guns and the LMT MWS and SR25 ACC and EMC. Also have had some on "exotics" AUG A2 HBAR, HK 93, and HK G3k. Nearly everything I've had in the last 10 years has been shot to at least 800y on 12x20" steel....and that includes the "old" 1.1-4x20mm on basic bitch 14.5" carbines.
This has been in the context of LE sniper as well as patrol use, classes, competition and most importantly, just general experimentation to see how far things can get pushed (which I'm to understand is what those 9hole guys do).
That being said, despite my feelings between models, and their various pro's and con's...
I've never felt hindered in making a shot due to lack of adj. parallax given the intended purpose of these optics.
Reticle, adjustments (or lack of), magnification (or lack of), optic quality are things I could say have been factors in certain models in being paired with Rifle/ammo combinations and overall being the limiting performance factor of the (Rifle/Ammo/Optic/Shooter) "System".
In my opinion, the LPVO should be about speed, simplicity, and quickness in a shooting solution and elevating a platform in those respects. Too many folks are either demanding more than what is intended and possibly not looking at right class of optics for their needs; or at the very least respecting the give/take or "no free lunch" of this style of optic.
TLDR: Emphatic "NO" it has not hindered me
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Can it be done with LPVO, yes, but always looking for ways to reduce error into the system. LPVO is "good enuf" and I can't stand "good enuf". Especially if chasing your tail with poi shifts on clip ons, thinking it's collimation or mounting issues. Hell, if "good enuf" is all that's needed, then leave parallax adjustment dial at 125,.... but at least I'd have a choice then.
That was without me "trying" to induce error and before I realized wtf was going on. Also realizing sometimes good positional vs bad positional. I could do the opposite, "try" and induce error, then see how much I get.... Then I could answer your question better.
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