Turbulent Turtle
F-TR competitor
Sigh.
ED glass, CA and mirage
- Thread starter Turbulent Turtle
- Start date
Sigh.
ronsatspokane
Gold $$ Contributor
That is very cool. Sounds like fun stuff. Good to know there are people around doing this. Do you guys blend our own glass or do you source from places like Schott?
ronsatspokane
Gold $$ Contributor
It has to be said that someone in the field may be able to tell which combination of aberrations are impacting an image by just glancing through the eye piece. I can't very easily.
All of the general optics shops buy their glass from one of the major makers like Schott, Ohara, Hoya, or CDGM (Chinese). And Corning for things like ultra-high purity Fused Silica. I understand Nikon makes their own glass, and they might be about the only exception. Even they probably buy some of it as well. Melting optical quality glass is a voodoo science that is very complicated and very few people understand... I certainly don't! So lens manufacturers generally buy pucks of glass that are a little bigger than the finished lens (either roughly molded to the near shape or core drilled from a large slab). There are a few supply houses that specialize in selling raw glass from the various manufacturers to the lens makers. A few lens makers buy the larger slabs of glass and cut their own, but usually only for the more commonly used glasses. There are well over a 100 different glasses you would need to stock otherwise! And some of those are expensive... we buy some lens blanks that are ~50mm in diameter and cost several hundred dollars before even being ground and polished into a lens!
People talk about using Schott glass and Germans make great glass. Yes, they do. And the Schott glass that was used may come from Germany, the US, Malaysia, or somewhere else! It's a German company but it's not all made there. Just like you can buy a Toyota made in the USA. And the Japanese (Ohara and Hoya) make glass that's just as good. And they all make equivalent glasses that can usually be interchanged such as N-BK7 from Schott or S-BSL7 from Ohara (but not all "equivalents" are truly that). A lot of lens prints will even state/list equivalent glasses that can be used. Each kinda has their own little specialty area as well where the competitors don't have a similar glass. Of course it doesn't matter who made the glass if the lens designer or manufacturer did a poor job! Being concerned about who made the glass for your scope is like being concerned about who made the steel for your action or barrel. If the proper material was chosen by the designer for the desired performance and the machinist made it correctly, it just doesn't matter to the consumer. It's the designers job to know who makes the right stuff.
Justin
ronsatspokane
Gold $$ Contributor
I kind of suspected it was the case that there are a lot of good glass makers out there. "Voodoo science", that cracks me up. In my minds eye I had always pictured an alchemist in a 17th century lab throwing different pieces of dirt into a crucible and melting it into a goo. 
In reality I'll bet that there is a lot of depth in materials science and the physics behind what works and what doesn't.
Thanks for answering the questions. Interesting stuff that many of us don't get to hear about.
In reality I'll bet that there is a lot of depth in materials science and the physics behind what works and what doesn't.Thanks for answering the questions. Interesting stuff that many of us don't get to hear about.
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Fred Bohl
Gold $$ Contributor
TT I'm going to offer a partial defense of your assertion above. We will assume your March scopes have been designed and built to minimize both spherical and chromatic aberrations as much as possible within the constraints of performance, weight and price. The primary effect of both CA and SA will be to slightly defocus the image. Since a rifle scope is a visual instrument (not a camera) your eye becomes the imager and your brain interprets the image. That slight defocus do to SA is monochromatic and will be interpreted as edge blur (defocus). CA will vary with color (frequency) and be interpreted as changing edge blur (changing defocus) and being dynamic will be more noticeable to your conscious mind.
TT I also agree with you that centering the scope produces a better image and more uniform/correct click size for small offsets. Therefore on my long range (>300) yards rigs I use Ivey BR30-50 elevation adjustable rings.
Turbulent Turtle
F-TR competitor
FB, you essentially took away my thunder with your answer. Curse you.
Most people do not understand that the human brain does a great deal to enable "vision"; the brain does a LOT of interpretation and adaptation to the image. This is one of the main reasons I NEVER trust or believe anyone's impressions when comparing scopes, especially when comparing with their current scope.
I was going to answer that whatever SA was in the image, it really didn't have the effect on the IQ compared to CA, especially under the influence of the heat shimmer (mirage) as the color bleeding would be much more detrimental to the IQ under those conditions.
HOWEVER...
All that said, I must emphasize again that the entire premise or foundation of my hypothesis (it's not even a theory,) is something I believe I have been observing over a period of years of long range competition with a variety of riflescopes, always looking at the same target at the same rifle range. It's been about 15 years since I shot my first F-Class match at BRI, 1000 yard range, and I have used a bunch of riflescopes over the years. This is all conjecture and empirical; I have no way, means or knowledge on how to confirm or inform. It will remain, for now, simply a hypothesis and we can debate to our heart's content.
Right now, I believe I am using the very best riflescope for the purpose and while I am still open to new breakthroughs, I believe this is about as good as it can get without an IC in the riflescope. If/when that happens, it will be a paradigm shift and I hop the NRA has rules to prevent that. I have the very bestest riflescope for the purpose and I have it setup so as to get the very best IQ from it; smack in the center.
I'm going to catch hell for this, but you talk about "calcium flouride." I'm betting you meant calcium "fluoride". There is a difference between flour and fluor.
However, the rest of your post was very interesting.
BTW, isn't Rochester ground zero for nuclear Armageddon according to Countersniper scopes according to their propaganda?
No, I meant calcium flouride... haven't you ever had one of those delicious lenses made from bread that help keep your bones strong!? You are missing out. I must say that it is a bit embarrassing that I let that one slip through, I certainly know better, but I am an engineer so spelling is optional! I guess there's a reason I normally write CaF2 instead.
I haven't heard the Armageddon thing before. But it inside the zone that was going to be part of Gillette's utopian metropolis that would house the entire population of the US! I think that is more scary.
Justin
Turbulent Turtle
F-TR competitor
Are those lenses gluten-free?
Coutnersniper had an advertising sheet years ago, (I wish I would have kept a copy), in which they said they were located in Rochester, NY, ground zero for a Soviet nuclear strike. I shit you not, that was a benefit for Countersniper scopes. The terminology they used to describe their lenses was unbelievable; they made up new elements on the spot. It was a classic. I'll keep searching the web to see if I can find it. It was also printed in gun rags. Remember those?
Turbulent Turtle
F-TR competitor
Wow. I found the verbiage:
http://media.midwayusa.com/pdf/reference/counter_sniper_instructions.pdf
Here is that fun part about Armageeddon.
"Borne of a decade of development for the sterile and untraceable optical rifle sighting requirements of Special Operations and clandestine warfare, CounterSniper™ Military Optical Gunsight Corp. manufactures a line of optical weapon sighting systems and visible and IR laser aiming systems from CQB to long range sniping and competition. The CMOG Titanium Line is the only tactical riflescope in the world UNCONDITIONALLY warranted for life. Battle damage, bomb damage, even bullet impacts are covered. If it is damaged unworkable, send it to us and we will fix it or give you a new one. CounterSniper™ Military Optical Gunsight Corp. is headquartered in Rochester NY, the imaging capital of the world. Long a primary Soviet nuclear impact target due to the creation of optical sighting systems for satellites, spy planes and now digital imaging devices, it is home to some of the premier optical creation, coating and imaging companies. The integration of these capabilities yield some of Americas most critical observation technologies. Among these are the world’s first extreme zoom range scopes, offering ranges of 1-8 power, 2-16 power and 3-24 power. For more info on these remarkable tools of the preservation of liberty, call us, see the web, or see your authorized CounterSniper™ Dealer."
You will notice they couldn't spell to save their life. The first word: "Borne", should be "Born". It goes downhill from there.
Then we see this:
• Forged and milled pure Titanium or T6061 aircraft aluminum bodies.
• Impact resistance to more than 5000 times the force of gravity.
• Lenses of utterly flawless transmissivity, composited to aspheric lens elements to eliminate chromatic aberrations with apochromatic lenses with Extra Low Dispersion Glass.
• Proprietary-230-+485*F degree stable pure optical glass
• 24 step vacuum Bertrillium-Zantitium™ multicoating, raises the light transmission coefficients to beyond anything previously possible.
• Massive 56mm primary objective lenses offer nearly triple the light transmission area of lesser designs.
• Vacuum and lifetime sealed with a mixture of nitrogen and rare earth gasses.
http://media.midwayusa.com/pdf/reference/counter_sniper_instructions.pdf
Here is that fun part about Armageeddon.
"Borne of a decade of development for the sterile and untraceable optical rifle sighting requirements of Special Operations and clandestine warfare, CounterSniper™ Military Optical Gunsight Corp. manufactures a line of optical weapon sighting systems and visible and IR laser aiming systems from CQB to long range sniping and competition. The CMOG Titanium Line is the only tactical riflescope in the world UNCONDITIONALLY warranted for life. Battle damage, bomb damage, even bullet impacts are covered. If it is damaged unworkable, send it to us and we will fix it or give you a new one. CounterSniper™ Military Optical Gunsight Corp. is headquartered in Rochester NY, the imaging capital of the world. Long a primary Soviet nuclear impact target due to the creation of optical sighting systems for satellites, spy planes and now digital imaging devices, it is home to some of the premier optical creation, coating and imaging companies. The integration of these capabilities yield some of Americas most critical observation technologies. Among these are the world’s first extreme zoom range scopes, offering ranges of 1-8 power, 2-16 power and 3-24 power. For more info on these remarkable tools of the preservation of liberty, call us, see the web, or see your authorized CounterSniper™ Dealer."
You will notice they couldn't spell to save their life. The first word: "Borne", should be "Born". It goes downhill from there.
Then we see this:
• Forged and milled pure Titanium or T6061 aircraft aluminum bodies.
• Impact resistance to more than 5000 times the force of gravity.
• Lenses of utterly flawless transmissivity, composited to aspheric lens elements to eliminate chromatic aberrations with apochromatic lenses with Extra Low Dispersion Glass.
• Proprietary-230-+485*F degree stable pure optical glass
• 24 step vacuum Bertrillium-Zantitium™ multicoating, raises the light transmission coefficients to beyond anything previously possible.
• Massive 56mm primary objective lenses offer nearly triple the light transmission area of lesser designs.
• Vacuum and lifetime sealed with a mixture of nitrogen and rare earth gasses.
Fred Bohl
Gold $$ Contributor
Attachments
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Turbulent Turtle
F-TR competitor
I've had a little discussion about my hypothesis that ED/Super ED glass is less affected by mirage compared to regular glass, at another forum that snipes at everything and likes to hide.
During the discussion, I came up with this attempt at an explanation as to why this could be something valid. I'm reposting it here in the hope that I would get some constructive comments that would either confirm or infirm my thinking.
---
There are essentially three areas that make up a riflescope and they each have a bearing on the magnification of the image. These areas are the objective lens group, the erector tube and the eyepiece. The magnification range of a riflescope is a combination of these three sections. For a 5-50X56 like my long-used and superb March-X scope, the base magnification (5X) is the objective group focal length divided by the eyepiece focal length. The 5 to 50 is, you guessed it, the 10X zoom ratio afforded by the erector tube assembly.
A riflescope essentially forms an image at the first focal plane that is somewhat magnified and from that point on, the erector assembly zooms in on that image to project a magnified portion of that image on the second focal plane which is in turn, inspected by the eyepiece, an afocal optics that then transmits the light to the eye. If you compare my 5-50X56 to a spotting scope, you would have to compare it to a very weak spotting scope. My Kowa is a 27X with the LER eyepiece. I also have a zoom eyepiece, but the zoom is done in the eyepiece not in the scope body. The base 22x of my zoom eyepiece is what you would compare to the base 5X of my March.
The zoom assemblies, whether in the eyepiece or erector tube only magnify the image presented at the first focal plane in front of the erector tube in my riflescope or at the prism in my Kowa.
We have seen in this thread that people turn down the magnification when the mirage gets bad. Camera buffs like me know not to use long lenses when shooting through mirage. The longer the focal length to the first focal plane (or camera sensor), the more the image will be distorted by the mirage because it’s compressing more distortion in the atmosphere. In a riflescope, after the first focal plane, the image will not be catching any more mirage, there are no atmospheric conditions in the scope further distorting the light rays. What is happening however, is that zooming in on the first focal plane is bringing out the distortion the image may have from the mirage. So it is important to get as clear and crisp an image in the first focal plane as possible so as not to detect the distortion.
Think of it as the photographer taking a picture (the first focal plane) and then zooming in on the image the camera sensor captured. Further this image is static, frozen in time, which highlights any moving distortion, unlike a riflescope in which everything is in motion, fluidic. Let’s say you take a picture with a 200mm lens onto a 35mm sensor. Right off the bat, you have 4X, as a normal lens is about 50mm. If you make an 8X10 of that picture, you zoomed 8X, so the 8X10 picture is a 32X representation of the subject. Now, let’s say you take the same picture and you want to keep at 32X overall. If you use a light telephoto like a 100mm, you would need to blow it up to a 16X20 to get the same results. Of course, we could only look at the picture through a hole about an inch and some in diameter, (the eyepiece of the riflescope). Now if the resolution is low (think number of pixels), blowing up an image that much will create some issues. This is where glass quality comes in. Great glass will provide a higher resolution image and you will be able to distinguish objects properly even at large magnification. Now if mirage gets into the action and you started with oh-hum quality glass, the image that looked fine when the air was still gets jumbled up more quickly when the mirage comes in to distort the image. If the pixel count is merely adequate to blow up to 32X, adding the mirage distortion is going to mess up that image faster than if I started with a higher pixel count image and blew it up to 32X.
With the higher pixel count image be immune to the mirage? Not on your life, but it won’t be as bad as for the lower pixel count image. Now adding the chromatic aberration effect of lower quality glass resulting in lower contrast and you can really mess up an image with mirage.
The goal is to provide the very best image to the first focal plane, with the best contrast and highest resolution possible. When people turn down the magnification of their scope, they are just reducing the magnification after the first focal plane. They are not reducing the focal length of a telephoto or telescope. A spotting scope inherently has a long primary focal length, but it also has a larger objective, which I think helps the image quality (resolution), but only up to a point which I believe is less than in a riflescope.
The image at the first focal plane of my March-X 10-60X56 HM happens to have incredibly high resolution, excellent contrast, and very low aberration. I see the mirage, I detect the effect of the mirage but it doesn’t mess up the picture to the point I can’t see the rings on the target distinctly.
---
That pretty much shut down the discussion there. Either it was over everyone's head or it was so far off the reservation it was not worth discussing.
I was at a match last Sunday, shooting at 50X at 1000 yards and loving it. 50X is my new normal. The lines on the target wereshimmering twinkling, vibrating, the mirage was miraging, but it was clear and I could place my center dot exactly where I wanted it to be.
During the discussion, I came up with this attempt at an explanation as to why this could be something valid. I'm reposting it here in the hope that I would get some constructive comments that would either confirm or infirm my thinking.
---
There are essentially three areas that make up a riflescope and they each have a bearing on the magnification of the image. These areas are the objective lens group, the erector tube and the eyepiece. The magnification range of a riflescope is a combination of these three sections. For a 5-50X56 like my long-used and superb March-X scope, the base magnification (5X) is the objective group focal length divided by the eyepiece focal length. The 5 to 50 is, you guessed it, the 10X zoom ratio afforded by the erector tube assembly.
A riflescope essentially forms an image at the first focal plane that is somewhat magnified and from that point on, the erector assembly zooms in on that image to project a magnified portion of that image on the second focal plane which is in turn, inspected by the eyepiece, an afocal optics that then transmits the light to the eye. If you compare my 5-50X56 to a spotting scope, you would have to compare it to a very weak spotting scope. My Kowa is a 27X with the LER eyepiece. I also have a zoom eyepiece, but the zoom is done in the eyepiece not in the scope body. The base 22x of my zoom eyepiece is what you would compare to the base 5X of my March.
The zoom assemblies, whether in the eyepiece or erector tube only magnify the image presented at the first focal plane in front of the erector tube in my riflescope or at the prism in my Kowa.
We have seen in this thread that people turn down the magnification when the mirage gets bad. Camera buffs like me know not to use long lenses when shooting through mirage. The longer the focal length to the first focal plane (or camera sensor), the more the image will be distorted by the mirage because it’s compressing more distortion in the atmosphere. In a riflescope, after the first focal plane, the image will not be catching any more mirage, there are no atmospheric conditions in the scope further distorting the light rays. What is happening however, is that zooming in on the first focal plane is bringing out the distortion the image may have from the mirage. So it is important to get as clear and crisp an image in the first focal plane as possible so as not to detect the distortion.
Think of it as the photographer taking a picture (the first focal plane) and then zooming in on the image the camera sensor captured. Further this image is static, frozen in time, which highlights any moving distortion, unlike a riflescope in which everything is in motion, fluidic. Let’s say you take a picture with a 200mm lens onto a 35mm sensor. Right off the bat, you have 4X, as a normal lens is about 50mm. If you make an 8X10 of that picture, you zoomed 8X, so the 8X10 picture is a 32X representation of the subject. Now, let’s say you take the same picture and you want to keep at 32X overall. If you use a light telephoto like a 100mm, you would need to blow it up to a 16X20 to get the same results. Of course, we could only look at the picture through a hole about an inch and some in diameter, (the eyepiece of the riflescope). Now if the resolution is low (think number of pixels), blowing up an image that much will create some issues. This is where glass quality comes in. Great glass will provide a higher resolution image and you will be able to distinguish objects properly even at large magnification. Now if mirage gets into the action and you started with oh-hum quality glass, the image that looked fine when the air was still gets jumbled up more quickly when the mirage comes in to distort the image. If the pixel count is merely adequate to blow up to 32X, adding the mirage distortion is going to mess up that image faster than if I started with a higher pixel count image and blew it up to 32X.
With the higher pixel count image be immune to the mirage? Not on your life, but it won’t be as bad as for the lower pixel count image. Now adding the chromatic aberration effect of lower quality glass resulting in lower contrast and you can really mess up an image with mirage.
The goal is to provide the very best image to the first focal plane, with the best contrast and highest resolution possible. When people turn down the magnification of their scope, they are just reducing the magnification after the first focal plane. They are not reducing the focal length of a telephoto or telescope. A spotting scope inherently has a long primary focal length, but it also has a larger objective, which I think helps the image quality (resolution), but only up to a point which I believe is less than in a riflescope.
The image at the first focal plane of my March-X 10-60X56 HM happens to have incredibly high resolution, excellent contrast, and very low aberration. I see the mirage, I detect the effect of the mirage but it doesn’t mess up the picture to the point I can’t see the rings on the target distinctly.
---
That pretty much shut down the discussion there. Either it was over everyone's head or it was so far off the reservation it was not worth discussing.
I was at a match last Sunday, shooting at 50X at 1000 yards and loving it. 50X is my new normal. The lines on the target were
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Fred Bohl
Gold $$ Contributor
Denys,
Re your post #52 - I admit to being old (75) and past my best mental abilities so it took me three careful and thoughtfull reads to understand your 'explanation'.
After reading all your informative posts (thank you for those) I'm still somewhat unsettled as to what you are meaning by mirage versus shimmering. Could you please give us your 'explanation' of the these. Please try to use shorter sentences and monosyllabic words for us old folks.
Re your post #52 - I admit to being old (75) and past my best mental abilities so it took me three careful and thoughtfull reads to understand your 'explanation'.
After reading all your informative posts (thank you for those) I'm still somewhat unsettled as to what you are meaning by mirage versus shimmering. Could you please give us your 'explanation' of the these. Please try to use shorter sentences and monosyllabic words for us old folks.
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Turbulent Turtle
F-TR competitor
@Fred Bohl Thanks for pointing that out. I was actually a little hesitant when I wrote that sentence thinking the use of "shimmering" might be confusing especially in light of my earlier diatribe about the misnomer "mirage" and its usage.
I went ahead an edited my post to remove the confusion I caused. What I see in my scope when the mirage is heavy is that the lines on the target seem to be alive, electrified even, sparkling and vibrating, but definitely clean and very distinct. I hope this clears it up for you and @SPJ .
Turbulent Turtle
F-TR competitor
I do not own a March 48X52 HM. I have never looked through one so I do not speak from first-hand experience.
The March 48X52, I believe, was the first one to get Super ED lenses. Now, there is a difference between a 52MM objective and 56MM objective. The 52mm objective is only 86% the size of the 56mm objective. Which means that it only allows through 86% of the light of the larger objective. (I hope I did the math correctly; pi*r-squared.) So at the same power (48 to 50X) and for the same quality of glass, the image through the 56mm objective will be somewhat brighter and have a little bit greater resolution compared to the 52mm objective. That's what the specs tell me, as I said, I never looked through a March 48X52 HM.
Beats me but it has all the HM bells and whistles , and it is a fixed power without the added lenses needed to make it a variable, also a lot lighter ...... jim
Ranger188
Silver $$ Contributor
Jim, that's what I'm thinking. Less glass to darken the light transmission thru the tube.
I've got to believe that the more lens, no matter how good they are, it's going to
affect the amount of light you see.
Has to be a trade off between amount of lenses to the objective diameter and power.
My old Sightron SIII 8-32x56 was one of the brightest scopes I've looked thru.
Had the 56mm objective, but no ED glass.
Sold it, so I can't compare it to my ED glass now. (clarity)
I've got to believe that the more lens, no matter how good they are, it's going to
affect the amount of light you see.
Has to be a trade off between amount of lenses to the objective diameter and power.
My old Sightron SIII 8-32x56 was one of the brightest scopes I've looked thru.
Had the 56mm objective, but no ED glass.
Sold it, so I can't compare it to my ED glass now. (clarity)
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