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Rifle Scopes Parallax vs Image Focus

Thank you very much . If the the parallax is not correct when the image is in sharp focus, can the scope manufacturer correct this if the scope is sent back to them?
 
Thank you very much . If the the parallax is not correct when the image is in sharp focus, can the scope manufacturer correct this if the scope is sent back to them?

They should be able to get this corrected. If I understood correctly, the OP mentions in his video that this is something very rarely seen in high end optics and more commom on budget scopes. Either or, the main goal of the scope maker is to align reticle and image all on the same focal plane in order to be able to eliminate any parallax all while have a crisp image. If after adjusting and playing around with the side focus you can only get one without the other (crisp image or to be completely parallax free), then the scope is defective.
 
If my eyesight is corrected to 20/20 with glasses, and my eyepiece is adjusted correctly, but the scope still has parallax at the ideal focus setting, and the manufacturer claims there’s nothing wrong with the scope then is it my eyesight/eyeglass that is causing this?
 
If my eyesight is corrected to 20/20 with glasses, and my eyepiece is adjusted correctly, but the scope still has parallax at the ideal focus setting, and the manufacturer claims there’s nothing wrong with the scope then is it my eyesight/eyeglass that is causing this?

It is physically impossible for two images to be on the same focal plane, yet one is out of focus and the other is not. That is how the parallax control removes parallax error. It brings one focal plane in line with another. If either the target or the reticle are blurry, then they are—by definition—not on the same plane of focus. That means either the diopter is set incorrectly or the parallax control is set incorrectly or there is a malfunction in the system somewhere. Maybe mirage plays a part in it as well...

If you see no parallax error, but the target is sharp and reticle is blurry = diopter set incorrectly (but I don't see how that's possible as you would have parallax error).
If you see no parallax error, but the target is blurry and reticle is sharp = diopter set incorrectly (but I don't see how that's possible as you would have parallax error).
If you see no parallax error, and target is sharp and reticle is sharp = everything good.
If you DO see parallax error, but target is sharp and reticle is sharp = I don't know (again, I don't see how that is possible).
 
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On my problem free scopes I have no problem adjusting the scope to my eyes. The ATACR was the only one out of two dozen scopes that caused this issue. I contacted another scope manufacturer that shall remain nameless who told me they believed there was misalignment in the lenses. I don’t know if you remember but when the BEAST was about to come out NF had a “ production issue “ that wasn’t ever discussed in detail. But now that I think about it it could have been related to the lens packs they buy from their vendors and possible misalignment. But I thought that misalignment manifests itself as CA. My ATACR had none.
 
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If you wear glasses, take them off and re-set the diopter on your problem scope and your known good scope. Test and repeat along the lines of FourT6and2's comment at post 7.
 
On my problem free scopes I have no problem adjusting the scope to my eyes. The ATACR was the only one out of two dozen scopes that caused this issue. I contacted another scope manufacturer that shall remain nameless who told me they believed there was misalignment in the lenses. I don’t know if you remember but when the BEAST was about to come out NF had a “ production issue “ that wasn’t ever discussed in detail. But now that I think about it it could have been related to the lens packs they buy from their vendors and possible misalignment. But I thought that misalignment manifests itself as CA. My ATACR had none.

I find it difficult to believe that a misaligned lens pack would yield any type of image that wasn't grossly distorted in some manner. There is little to no tolerance leeway when assembling a multi lens system
 
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If my eyesight is corrected to 20/20 with glasses, and my eyepiece is adjusted correctly, but the scope still has parallax at the ideal focus setting, and the manufacturer claims there’s nothing wrong with the scope then is it my eyesight/eyeglass that is causing this?

I have seen scopes being off and sometimes the manufacturer will just swap it out. It just depends on how far odd it is (typical culprit is placement of the reticle cell).

However, you can achieve the same effect by not focusing the eyepiece properly and, in my experience, it is extremely uncommon for people to take the time and do it right.

Astigmatism makes it trickier.

Each individual case is different, so all I can say is that before you send the scopoe back make sure you go through the eyepiece and side focus adjustments carefully and methodically.

ILya
 
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It is physically impossible for two images to be on the same focal plane, yet one is out of focus and the other is not. That is how the parallax control removes parallax error. It brings one focal plane in line with another. If either the target or the reticle are blurry, then they are—by definition—not on the same plane of focus. That means either the diopter is set incorrectly or the parallax control is set incorrectly or there is a malfunction in the system somewhere. Maybe mirage plays a part in it as well...

If you see no parallax error, but the target is sharp and reticle is blurry = diopter set incorrectly (but I don't see how that's possible as you would have parallax error). Correct. I do not see how you can have no parallax error with a blurry reticle unless there are major ophthalmic issues.
If you see no parallax error, but the target is blurry and reticle is sharp = diopter set incorrectly (but I don't see how that's possible as you would have parallax error). This a situation where the reticle plane is not quite in the right spot with respect to the erector optical system and your eye and brain make the reticle look sharper than it really is. We are really good in seeing sharp edges where there are none.
If you see no parallax error, and target is sharp and reticle is sharp = everything good.
If you DO see parallax error, but target is sharp and reticle is sharp = I don't know (again, I don't see how that is possible). This gets tricky again because of how our brains process images.

Mirage plays a part in it in a sense that it makes it difficult to figure out if you have a scope issue or environmental conditions make the target look weird.

See above in red.
 
Question: not meant to be inflammatory but to inform understanding - when was the last time OP got his eyes checked?

Reason being spectacle wearers can have problems shooting through the top, thick part of their lens (after focussing through the centre of the lens) and any eye degradation becomes more evident. This was the basis of my comment to zero two scopes (one working/one faulty) without wearing glasses.
 
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Question: not meant to be inflammatory but to inform understanding - when was the last time OP got his eyes checked?

Reason being spectacle wearers can have problems shooting through the top, thick part of their lens (after focussing through the centre of the lens) and any eye degradation becomes more evident. This was the basis of my comment to zero two scopes (one working/one faulty) without wearing glasses.

Technically, I am the original poster and I wear contacts. Oh, and I had my eyes checked three weeks ago. No changes for the last seventeen years and very slight astigmatism.

ILya
 
Great explanation ILya. Thanks again for taking the time to share your knowledge.
 
Technically, I am the original poster and I wear contacts. Oh, and I had my eyes checked three weeks ago. No changes for the last seventeen years and very slight astigmatism.

ILya

Sorry - I meant 918v. I see too many guys who refuse to update their glasses and then shoot through the thick part and wonder why the targets are awful.
 
If you DO see parallax error, but target is sharp and reticle is sharp = I don't know (again, I don't see how that is possible).
I have experienced a touch of this in a TT 5-25, and I think that it has to do with the depth of field in the optic.

Situationally, it has happened while shooting prairie dogs... where there are virtually no large landmarks to use for helping to judge distance, it's often difficult to judge the difference in distance between a small 'dog/mound at 250 yards and a large dog/mound at 400 yards. The depth of field of the TT is such that both targets will be in focus, but I can experience parallax error on either target (depending on how the parallax is adjusted). With nothing in the field of fire to use as a good "target" for setting parallax/focus, I find myself moving my head around the eye box checking for parallax error when I move from one part of the 'dog town to another.
 
I have experienced a touch of this in a TT 5-25, and I think that it has to do with the depth of field in the optic.

Situationally, it has happened while shooting prairie dogs... where there are virtually no large landmarks to use for helping to judge distance, it's often difficult to judge the difference in distance between a small 'dog/mound at 250 yards and a large dog/mound at 400 yards. The depth of field of the TT is such that both targets will be in focus, but I can experience parallax error on either target (depending on how the parallax is adjusted). With nothing in the field of fire to use as a good "target" for setting parallax/focus, I find myself moving my head around the eye box checking for parallax error when I move from one part of the 'dog town to another.

I understand. Valid point. I'd say in response to that, Depth of Field in this context is not a set point. It's a "field" that ranges from out of focus, to slightly in focus, to in focus, to tack sharp at the center, and then gradually fades back to out of focus again. And in the case of your scope, I can see how one might have a sharp target and reticle yet still have parallax. So, good point about Depth of Field being wide vs narrow. Just gotta make sure your target is right at that perfectly in-focus point, which is sometimes easier said than done. :)
 
Thank you ILya for that informative presentation. I get a lot out of your little videos. Maybe you can touch on a couple other subjects that tend to come up related to parallax and focus:

Forgiving parallax - the situation where some scopes make it very difficult to get precise parallax correction whereas other scopes are parallax free throughout a pretty broad range. While I really like March scopes, they do tend to have finicky parallax and you have to be a little more precise with your adjustments with the 3-24x series. I have experienced that my parallax on my AMG is much more forgiving and in fact, if I recall correctly, when Frank reviewed the AMG he mentioned that he shot a competition with it where he left it on one setting and shot both short range and long range targets the rest of the day without having to adjust parallax. So my question is this, why are some scope designs more forgiving when it comes to parallax adjustment and do higher magnification erector assemblies tend to have more of an issue vs. lower magnification (8x vs 4x).

Diopter - The idea behind the diopter is to get the reticle to be in focus when you are looking through the scope. Because FFP scopes are more finicky than SFP scopes in regard to reticle sharpness it is especially important to setup the diopter appropriately. There is a sticky on the scope forum here for setting up your diopter appropriately (and I have seen that recommendation in manufacturer's manuals as well - yes, I often do read through those manuals even though I'm a guy :D); however, I have had issues with this at times in that my eyes seem to tell my brain that the reticle is in focus through a broad range of the dioptric adjustment. My expectation is that it would be obvious, kind of like using the parallax as a side focus and seeing when the image is in good focus, but it's not obvious to my eyes which gives me false positives when I'm setting the diopter. Maybe it's the fact that I have 20/15 vision or that I'm getting older and my eyes are lazier (thought it would seem the opposite would be at play), I don't know but I have found this method to be difficult. My question is this, what exactly is the diopter adjusting to get that reticle to be sharp and why is it different for each person? Is it similar to reading glasses where it is adjusting to correct for the fact that I cannot focus on close objects like I used to?

When hk dave posted his comparison of the TT, Minox, Nightforce, Schmidt and Vortex Gen II he mentioned the very same thing I experience with the diopter setting where my eye seems to adjust very quickly thus making it difficult when I quickly look through the scope and look away for 5 seconds. I have learned that tweaking the diopter after setting parallax properly and looking at an image (not the sky or white backdrop but at an actually object) at different distances actually helps me set the diopter (or reticle) more accurately, why is this? I have also observed where a diopter that is adjusted in the extreme can actually distort or blur the image some, if the diopter is purely for making sure the reticle is sharp, how does it distort the overall image if not setup properly?

When I first receive a scope it takes me some time to get the diopter/reticle setup correctly and I wonder if others experience this issue? I also wonder if maybe more issues that we hear on threads about scope X being better than scope Y when it comes to overall clarity may be affected by an improperly set diopter?
 
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Thank you ILya for that informative presentation. I get a lot out of your little videos. Maybe you can touch on a couple other subjects that tend to come up related to parallax and focus:

Forgiving parallax - the situation where some scopes make it very difficult to get precise parallax correction whereas other scopes are parallax free throughout a pretty broad range. While I really like March scopes, they do tend to have finicky parallax and you have to be a little more precise with your adjustments with the 3-24x series. I have experienced that my parallax on my AMG is much more forgiving and in fact, if I recall correctly, when Frank reviewed the AMG he mentioned that he shot a competition with it where he left it on one setting and shot both short range and long range targets the rest of the day without having to adjust parallax. So my question is this, why are some scope designs more forgiving when it comes to parallax adjustment and do higher magnification erector assemblies tend to have more of an issue vs. lower magnification (8x vs 4x).

Diopter - The idea behind the diopter is to get the reticle to be in focus when you are looking through the scope. Because FFP scopes are more finicky than SFP scopes in regard to reticle sharpness it is especially important to setup the diopter appropriately. There is a sticky on the scope forum here for setting up your diopter appropriately (and I have seen that recommendation in manufacturer's manuals as well - yes, I often do read through those manuals even though I'm a guy :D); however, I have had issues with this at times in that my eyes seem to tell my brain that the reticle is in focus through a broad range of the dioptric adjustment. My expectation is that it would be obvious, kind of like using the parallax as a side focus and seeing when the image is in good focus, but it's not obvious to my eyes which gives me false positives when I'm setting the diopter. Maybe it's the fact that I have 20/15 vision or that I'm getting older and my eyes are lazier (thought it would seem the opposite would be at play), I don't know but I have found this method to be difficult. My question is this, what exactly is the diopter adjusting to get that reticle to be sharp and why is it different for each person? Is it similar to reading glasses where it is adjusting to correct for the fact that I cannot focus on close objects like I used to?

When hk dave posted his comparison of the TT, Minox, Nightforce, Schmidt and Vortex Gen II he mentioned the very same thing I experience with the diopter setting where my eye seems to adjust very quickly thus making it difficult when I quickly look through the scope and look away for 5 seconds. I have learned that tweaking the diopter after setting parallax properly and looking at an image (not the sky or white backdrop but at an actually object) at different distances actually helps me set the diopter (or reticle) more accurately, why is this? I have also observed where a diopter that is adjusted in the extreme can actually distort or blur the image some, if the diopter is purely for making sure the reticle is sharp, how does it distort the overall image if not setup properly?

When I first receive a scope it takes me some time to get the diopter/reticle setup correctly and I wonder if others experience this issue? I also wonder if maybe more issues that we hear on threads about scope X being better than scope Y when it comes to overall clarity may be affected by an improperly set diopter?

There are a couple of ways to think about depth of field and I need to give some thought to which way makes for a better explanation. I think I can verbalize it adequately with a couple of sketches and using nothing beyond simple geometry, but it will take a little thought. I am out of town this weekend. When I return, I will put together another video or two to cover this.

ILya
 
There are a couple of ways to think about depth of field and I need to give some thought to which way makes for a better explanation. I think I can verbalize it adequately with a couple of sketches and using nothing beyond simple geometry, but it will take a little thought. I am out of town this weekend. When I return, I will put together another video or two to cover this.

ILya

I find photos to be helpful. If anybody is familiar with photography, this should be a no brainer.

focus3.jpg


depth-of-field-by-f-stop-comparison.jpg


Not really for you, Koshkin. But for anybody else still wondering: All the parallax setting on a scope does is shift the focal point forward or backward in the field of view until the in-focus part of the image and the reticle are both on the same plane. I know you know this, but in case other people were still trying to wrap their head around it. :) And one scope might have a thinner or narrower Depth of Field (f/1.8 in the image above) than another with a thicker or wider Depth of Field (f/22 above). The scope with a thinner DoF will be easier to more precisely set parallax and get a sharp target because it's range of in-focus area is smaller, and thus easier to see. Whereas a scope with a larger DoF might have more of a range with regard to a sharp target, but it can make finding the exact sweet spot more difficult.

In the f/22 image above, where is the exact center/sweet spot of the DoF where the image is perfectly sharp? Now compare that to the f/1.8 image. Which one is easier and faster to spot?

Some people talk about a scope having "forgiving" parallax and how they can just set it one point and not touch it for shooting targets at different distances. Well, this is not actually true. The scope's DoF is large, so it looks like your targets at various distances are focused, but you'll still have parallax error because technically the error is only gone at one specific setting for a target at a given distance. In f/22 image, which bottle cap is perfectly focused? Now the bottle cap below or above that one is still pretty sharp, but if this were a rifle scope, either of those bottle caps would still show parallax error. You need to adjust your parallax either way. UNLESS... your target is "at infinity" for your scope...

That would mean the distance at which you're shooting is far enough away that the in-focus (and parallax-free portion of your sight picture) covers a large enough physical distance. Let's pretend the in-focus area of your scope covers maybe 1/8th inch within your scope's sight picture. An 1/8th-inch portion of your picture at 100 yards might be a foot. But an 1/8th-inch portion of your picture at 1,200 yards might be 200 yards.
 
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I find photos to be helpful. If anybody is familiar with photography, this should be a no brainer.

focus3.jpg


depth-of-field-by-f-stop-comparison.jpg


Not really for you, Koshkin. But for anybody else still wondering: All the parallax setting on a scope does is shift the focal point forward or backward in the field of view until the in-focus part of the image and the reticle are both on the same plane. I know you know this, but in case other people were still trying to wrap their head around it. :) And one scope might have a thinner or narrower Depth of Field (f/1.8 in the image above) than another with a thicker or wider Depth of Field (f/22 above). The scope with a thinner DoF will be easier to more precisely set parallax and get a sharp target because it's range of in-focus area is smaller, and thus easier to see. Whereas a scope with a larger DoF might have more of a range with regard to a sharp target, but it can make finding the exact sweet spot more difficult.

In the f/22 image above, where is the exact center/sweet spot of the DoF where the image is perfectly sharp? Now compare that to the f/1.8 image. Which one is easier and faster to spot?

Some people talk about a scope having "forgiving" parallax and how they can just set it one point and not touch it for shooting targets at different distances. Well, this is not actually true. The scope's DoF is large, so it looks like your targets at various distances are focused, but you'll still have parallax error because technically the error is only gone at one specific setting for a target at a given distance. In f/22 image, which bottle cap is perfectly focused? Now the bottle cap below or above that one is still pretty sharp, but if this were a rifle scope, either of those bottle caps would still show parallax error. You need to adjust your parallax either way. UNLESS... your target is "at infinity" for your scope...

That would mean the distance at which you're shooting is far enough away that the in-focus (and parallax-free portion of your sight picture) covers a large enough physical distance. Let's pretend the in-focus area of your scope covers maybe 1/8th inch within your scope's sight picture. An 1/8th-inch portion of your picture at 100 yards might be a foot. But an 1/8th-inch portion of your picture at 1,200 yards might be 200 yards.

Good explanation, although for riflescopes there is a bit more to it simply because of how they are built.

I'll address it next week when I get back in town and have my whiteboard available.

ILya
 
Thank you FourT, you and I both have photography backgrounds so this really resonates with me and understand, like you, the whole concept of depth of field. I understand that the diopter adjustment is attempting to get the reticle on the same focal plane as the image but why do so many (myself included) struggle with getting the two just right? Is it possible that some of us have eyes that adjust quicker than others thus making it more difficult to find the "sweet spot"? Back when I started in photography I had an old Minolta with a split prism view finder and I loved how it helped to get in focus shots with manual focus lenses:

I wish there was something like this for adjusting the diopter in order to better see how the reticle is aligned with a distant image. On a DSLR, I find it pretty easy to set the diopter for my eyes, I can quickly see when the image goes from being somewhat blurry to being sharply focused (assuming the AF has done it's job and produced an in focus image in parallel with the sensor). Back to rifle scopes, we have parallax adjustment which allows us to focus the scope at different distances; however, as ILya points out the focus doesn't always coincide with the appropriate parallax setting and to get a truly parallax free image the final image through the scope may be slightly out of focus. ILya, you responded with depth of field (DOF) regarding my question about fine tuning the diopter/reticle and wonder what DOF has to do with setting the diopter properly so I am very curious to read that post or watch that video. Most of us have eyes that are pretty quick to tell our brains that an image is in focus; however, when we get to the diopter and getting that reticle to be on the proper plane with the image when setting our scopes to infinity (∞ on the parallax dial) and looking at the sky or bright wall, turning away for 5 seconds and quickly looking again, well for those of us who have difficulty with doing that, I wonder if there is a better way. This is why I fine tune the diopter after I go through the sky method when looking at targets at range; however, if this is actually detrimental then let me know as my desire is to setup my scopes to get the best possible image and reticle performance out of them.
 
I understand that the diopter adjustment is attempting to get the reticle on the same focal plane as the image

That is incorrect. The diopter adjustment simply focuses the reticle to your eye. Parallax control gets the reticle and target on same focal plane.

but why do so many (myself included) struggle with getting the two just right? Is it possible that some of us have eyes that adjust quicker than others thus making it more difficult to find the "sweet spot"?

No, I don't believe so. Just a matter of understanding the process of setting a scope up.

On a DSLR, I find it pretty easy to set the diopter for my eyes, I can quickly see when the image goes from being somewhat blurry to being sharply focused (assuming the AF has done it's job and produced an in focus image in parallel with the sensor).

I think you're getting two things confused here. The diopter on a camera doesn't focus what you're looking at. It's so you can get your viewfinder display focused (reticle, shutter speed, aperture, display, etc.).

and to get a truly parallax free image the final image through the scope may be slightly out of focus.

My point earlier was if this happens it means one's diopter isn't set properly. One just thinks it is. :) Or the scope is broken.

well for those of us who have difficulty with doing that, I wonder if there is a better way. This is why I fine tune the diopter after I go through the sky method when looking at targets at range; however, if this is actually detrimental then let me know as my desire is to setup my scopes to get the best possible image and reticle performance out of them.

There you go. You got it. That IS the better way. At least it's the only way I know of. Adjust your diopter by looking at a wall or sky or whatever. Then fine tune at distance by getting a target parallax-free and sharp, and then readjust diopter to match.
 
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Thank you for the clarification on exactly what the diopter setting is doing FourT. ILya explains it exactly as you mentioned, that the FFP optic and image plane are aligned by the parallax adjustment. So then the diopter is purely a focusing mechanism for the reticle itself, that being the case, why is there such a large range of adjustment even in the fast focus eyepieces? Is it because they are trying to accommodate such a vast array of different eyesight issues that customers have or is there another reason? I also didn't intend to imply that the diopter on a camera is actually focusing the image but adjusting the image due to my presbyopia so that the in focus image actually looks in focus to my eyes. I'm assuming the diopter on the scope is doing the same thing but I'm trying to understand the difficulty with setting the diopter on a scope vs a camera and maybe that's where ILya is going with the depth of field situation, when looking through my camera using an 85mm f/1.8 lens set at f/1.8 I can quickly see what is in focus and what is out of focus (similar to your image of the barbed wire) and therefore when I'm setting the diopter, because of the shallow depth of field, I am able to set it more easily; however, with the scope the depth of field is not so distinct (or at least it would appear) thus making it more difficult to set the diopter "easily".
 
Very good video. My only comment for improvement involves the audio. It seems to have been recorded very low-level. I'm on a laptop, but I had the computer volume and the video's volume maxed out and sitting in a quiet room and still found it difficult to hear. The next video I watched blasted me out of my chair, haha!
 
So then the diopter is purely a focusing mechanism for the reticle itself, that being the case, why is there such a large range of adjustment even in the fast focus eyepieces? Is it because they are trying to accommodate such a vast array of different eyesight issues that customers have or is there another reason?

That’s exactly it. I put my swaro on dad’s deer rifle this past season and I had the diopter almost all the way in with my glasses and Dad had always complained about my scopes. He screwed it almost all the way out and then he could finally see well enough to see fine print at 100 yards. It was nearly the entire adjustment range in difference.
 
Yeah, diopter has a large range to accommodate different people's eyes.
 
Very good video. My only comment for improvement involves the audio. It seems to have been recorded very low-level. I'm on a laptop, but I had the computer volume and the video's volume maxed out and sitting in a quiet room and still found it difficult to hear. The next video I watched blasted me out of my chair, haha!

I have been trying to figure out this whole sound business, but with very little luck so far. I think I will have to get a lapel microphone of some sort.
 
They should be able to get this corrected. If I understood correctly, the OP mentions in his video that this is something very rarely seen in high end optics and more commom on budget scopes. Either or, the main goal of the scope maker is to align reticle and image all on the same focal plane in order to be able to eliminate any parallax all while have a crisp image. If after adjusting and playing around with the side focus you can only get one without the other (crisp image or to be completely parallax free), then the scope is defective.

Wow! I guess there's a LOT of defective NXS out there! Nightforce refuses to recognize it as a problem.
 
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I have been trying to figure out this whole sound business, but with very little luck so far. I think I will have to get a lapel microphone of some sort.
I had to crank up the sound on my audio but I have external speakers that I can also crank so was able to hear you okay at max volume.
 
I have been trying to figure out this whole sound business, but with very little luck so far. I think I will have to get a lapel microphone of some sort.

That would sure do it.
 
I have been trying to figure out this whole sound business, but with very little luck so far. I think I will have to get a lapel microphone of some sort.

You can also use software to bump it up. I use Vegas for video editing and it has a Soundforge plug-in that allows you to compress and amplify the audio track. Easy and fast.
 
Every time I've had parallax error when the picture was sharp it was because I did not have the ocular set correctly for my eye.
 
Every time I had the ocular adjusted correctly for my eye the ATACR was out of focus when I removed parallax.
 
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I have seen scopes being off and sometimes the manufacturer will just swap it out. It just depends on how far odd it is (typical culprit is placement of the reticle cell).

However, you can achieve the same effect by not focusing the eyepiece properly and, in my experience, it is extremely uncommon for people to take the time and do it right.

Astigmatism makes it trickier.

Each individual case is different, so all I can say is that before you send the scope back make sure you go through the eyepiece and side focus adjustments carefully and methodically.

ILya

ILya, could you elaborate on your comment regarding astigmatism.
 
So does this mean that your diopter can cause parallax in an FFP scope?

I ask because I am fighting parallax with a Hensoldt ZF 6-24x72 SAM, it is a FFP scope. I have spent hours and hours messing with the parallax knob and just cant get the parallax out of the scope. I have even been tempted to have one of those huge parallax wheels made for the scope...

Is it possible the issue has been the diopter adjustment all along?

I thought I had the reticle in focus, but maybe I had that messed up all along. It would be good to know from an expert that the diopter can cause this problem. Would really help me with next steps on the scope.


It is physically impossible for two images to be on the same focal plane, yet one is out of focus and the other is not. That is how the parallax control removes parallax error. It brings one focal plane in line with another. If either the target or the reticle are blurry, then they are—by definition—not on the same plane of focus. That means either the diopter is set incorrectly or the parallax control is set incorrectly or there is a malfunction in the system somewhere. Maybe mirage plays a part in it as well...

If you see no parallax error, but the target is sharp and reticle is blurry = diopter set incorrectly (but I don't see how that's possible as you would have parallax error).
If you see no parallax error, but the target is blurry and reticle is sharp = diopter set incorrectly (but I don't see how that's possible as you would have parallax error).
If you see no parallax error, and target is sharp and reticle is sharp = everything good.
If you DO see parallax error, but target is sharp and reticle is sharp = I don't know (again, I don't see how that is possible).
 
Yes, diopter setting is absolutely critical for sharp reticle and target picture happening simultaneously with no parallax. I spend a significant amount of time setting diopter properly on an FFP scope. It's noticeably less critical on an SFP.
 
Very well explained, allthough - from what I understand - it's not just a badly adjusted erector system but it could also be manufacturing tolerances on all other parts involved that come into play. There is a lot of tolerance stacking happening in the optical system from what I have heard.

I have recently checked it and found that both on my Minox ZP5 and the Athlon BTR I have to sacrifice a tiny bit of image quality to get them parallax free. Now I always check it with headmovement (when I am in a stable position) and dont go just by image quality.
 
Not sure if this related or not but might take it for consideration...

If I wear my contacts, I can't focus up close and I can never get my diopter to focus. Not sure if others have noticed this but it's a problem for me.
 
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Tagging in to read this thread after work
I have struggled with this very issue, getting a nice clear picture vs no parallax
 
It is physically impossible for two images to be on the same focal plane, yet one is out of focus and the other is not.
This ^^.

I tried to listen to the video, but the man needs a real microphone if he wants to talk to def shooters like me! LOL

One of the small handful of presentations on the recent Modern Day Sniper symposium was the fella from Leupold. And his point was made firmly that, absent some sort of defect in the scope, if you adjust the "parallax" turrent to bring the target into the same sharp focus as the reticle, then you will have no parallax. His view, if I understood correctly, is that you adjust for optimum target focus and, again the presumption is that your diopter is also adjusted for optimum focus on the reticle.....and absent any defect in the scope....you cannot have parallax.

Now, when we say "plane" as in first or second focal plane....this is plane in the geometry sense of a two dimensional, depthless, surface. If both the reticle and the target are in optimum focus (at the same time) then they are focused, via the movement of the Barlow lens, in the same plane. Parallax, to my understanding, requires their to be some difference in focal length.

As for depth of field, to my mind this only makes the optimum target focus a bit more difficult to subjectively determine as being very slightly off may well look to to the shooter to be optimally focused...but its not. It may be pretty sharp, but its not optimal and therefore may be slightly off the plane from your reticle focus.

But there is some exact theoretical optimum and if both reticle and target at at optimum focus then they are on the same plane and parallax cannot exist.

Of course, I am more than willing to be corrected in any or all of this.

Cheers
 
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Thanks everyone! I will really really focus on getting the diopters correct and see what I get. My distance vision has been tested many times...so perhaps I have taken the diopters a little too lightly. Will report back with findings...

Been tempted to sell the scope...it has been driving me crazy....
 
This ^^.

I tried to listen to the video, but the man needs a real microphone if he wants to talk to def shooters like me! LOL

One of the small handful of presentations on the recent Modern Day Sniper symposium was the fella from Leupold. And his point was made firmly that, absent some sort of defect in the scope, if you adjust the "parallax" turrent to bring the target into the same sharp focus as the reticle, then you will have no parallax. His view, if I understood correctly, is that you adjust for optimum target focus and, again the presumption is that your diopter is also adjusted for optimum focus on the reticle.....and absent any defect in the scope....you cannot have parallax.

Now, when we say "plane" as in first or second focal plane....this is plane in the geometry sense of a two dimensional, depthless, surface. If both the reticle and the target are in optimum focus (at the same time) then they are focused, via the movement of the Barlow lens, in the same plane. Parallax, to my understanding, requires their to be some difference in focal length.

As for depth of field, to my mind this only makes the optimum target focus a bit more difficult to subjectively determine as being very slightly off may well look to to the shooter to be optimally focused...but its not. It may be pretty sharp, but its not optimal and therefore may be slightly off the plane from your reticle focus.

But there is some exact theoretical optimum and if both reticle and target at at optimum focus then they are on the same plane and parallax cannot exist.

Of course, I am more than willing to be corrected in any or all of this.

Cheers

Correct.

And if anybody out there reading this is a photographer and works with SLR cameras, then this should all make sense and actually be rather elementary. This is also why I PREFER scopes with very narrow depth of field. It makes it easier to eliminate parallax and find the very center of that focal field for a perfectly focused target. Wider depth of field makes the scope more forgiving for shooting multiple targets and different distances without having to touch your parallax (sort of ). But it also means it's harder to nail perfect target focus for zero parallax.

Personally, I have no need to engage multiple targets at difference distances super fast. I do a PRS-style match here or there, so it's not needed quite as much for me. And I'm not engaging live targets in combat. So I can take my time and readjust parallax when needed.
 
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Some great info in this thread. I’d like to throw two cents in the bucket, being the human
eyeball . Past few days have been spent at the range for 10 hours. Yesterday I became a
bit dehydrated and found I was missing my favourite 2.5 inch practice gong @ 500 meters,
when making a perfect wind call. Suspected aero jump or mirage, but reticle was a bit
blurry so Iwound diopter out a bit and elevation on target was perfect again. Wonder
how many people blame the solver when it’s actually parallax error, mirage displacement
etc?

Today I made sure I had enough water, and had to wind the diopter back in to yesterday
mornings’ setting. So despite same scope, rifle, ammo, target and (similar) wind conditions,
the biggest variable was me and my dehydrated eyeball.....