Rifle Scopes ED Glass and Super ED Glass

[Ape_Factory]

Appreciate the explanation Denys. Sometimes it's just understanding WHAT you're seeing so thank you for that.

If you reduce camera lenses and scopes down to glass elements trying to focus the visible light spectrum on the same focal plane, they're really not different but I understand where you're coming from on the IQ comment. The fewer glass elements (ED or otherwise), the more contrast and light transmission there is on said focal plane. Once you start getting into lenses with more elements and more element groups, it's really tough to keep the contrast level up and there's a loss in clarity as a result. I suspect the same thing happens in scopes. Certain designs have fewer elements with higher quality glass and multi coatings and there's a resulting uptick in IQ. It'd be interesting to know just how many elements and element groups are in a particular scope.

I still don't fully understand how a lens is able to minimize mirage though. Mirage is literally atmospheric conditions refracting light and causing image displacement by the end viewer. That light is already manipulated prior to entering the lens. Once it gets hot out, I'll have to go out and examine mirage through my Cronus which is the longest scope I have (29X) with everything you mentioned. Hopefully I can walk away with a better understanding! Again, appreciate the explanation.

 

[Convex]

Let me say it's a pleasure to peruse how you articulate your questions distilling the issues in a clear and cogent way.

You said this.....

......."Once you start getting into lenses with more elements and more element groups, it's really tough to keep the contrast level up and there's a loss in clarity as a result. I suspect the same thing happens in scopes. Certain designs have fewer elements with higher quality glass and multi coatings and there's a resulting uptick in IQ.".......

It's always been my understanding that these multi-element optics w/complex lens formulas don't work w/o the modern multicoating's and that the designers of some of these optics include the performance of these sophisticated coatings in incorporating more glass/designing complex lens formulas including more glass.

That's of course in light of the fact that every time you include another piece of glass in an optic, some of the light hitting that glass will reflect/deflect in a direction other than going through the glass toward the rear of the optic, along w/dispersion where some light hitting the glass doesn't make it through the glass itself and is also lost.


Yes, those two problems, getting as much light through the glass instead of bouncing off in the wrong direction, and dispersion where some of the light hitting the glass and headed in the right direction toward the rear of the optic doesn't make through the glass itself which combine to knock down light transmission and contrast along w/making what you see through the optic darker..

Every time a glass is added to a system there's additional light loss/loss of transmission, and that light loss because of so many elements, adds up/it's cumulative as to a % loss in transmission.


I know U know all this, I just mentioned it in passing for the folks that may not be familiar w/this.


I have a March top tier optic, the HM 4.5-28X52, but I don't have the 10-60 or the longer March optic Denys is discussing, so I'd defer to Denys and what he's saying.

I'll tell U what my take is on this, and I would say to Denys correct me if I'm wrong.

What I get from what he's mentioned is that between non-ED, ED, and Super ED glass, the mirage he's looking at is still "MESSED UP" IQ wise regardless of which glass is resolving his target, but that there are differences in the glass to where w/his prototype he can make out a shape he can still use to aim at/when aiming at the target he described.

If I'm understanding this correctly, what Denys is saying makes sense in that the three types of glass are going to present IQ differently, even if slightly different, and so it's not where "something leaps out of the lens and swats mirage on the ass", but manipulating the glass in the optic where the IQ is STILL MESSED UP, and w/it still messed up, Denys can still make out a shape he can aim at w/higher magnification than the other folks he mentioned who had to lower their magnification to deal w/the same mirage.


Not changing the mirage, but refining the optic to where w/the IQ STILL MESSED UP, a way is found to aim accurately at a higher magnification.

That makes sense to me, but I'll defer to Denys if I'm "way off the mark".

 

[MarkyMark007]

Every time a glass is added to a system there's additional light loss/loss of transmission, and that light loss because of so many elements, adds up/it's cumulative as to a % loss in transmission.

that's why I loose control every time when someone says that scopes with a lot of lences and high zoom ratio will be the best on the market.
and with march 10× zoom means more lences and worse picture than 3× zoom. pure physics.

 

[MarkyMark007]

Appreciate the explanation Denys. Sometimes it's just understanding WHAT you're seeing so thank you for that.

If you reduce camera lenses and scopes down to glass elements trying to focus the visible light spectrum on the same focal plane, they're really not different but I understand where you're coming from on the IQ comment. The fewer glass elements (ED or otherwise), the more contrast and light transmission there is on said focal plane. Once you start getting into lenses with more elements and more element groups, it's really tough to keep the contrast level up and there's a loss in clarity as a result. I suspect the same thing happens in scopes. Certain designs have fewer elements with higher quality glass and multi coatings and there's a resulting uptick in IQ. It'd be interesting to know just how many elements and element groups are in a particular scope.

I still don't fully understand how a lens is able to minimize mirage though. Mirage is literally atmospheric conditions refracting light and causing image displacement by the end viewer. That light is already manipulated prior to entering the lens. Once it gets hot out, I'll have to go out and examine mirage through my Cronus which is the longest scope I have (29X) with everything you mentioned. Hopefully I can walk away with a better understanding! Again, appreciate the explanation.

imho just like you explained.

problably human eye can see better through mirage with different light spectrum than when every wavelengths are represented like on the target.

and that's why with different producers, you will see different tint of picture when you look through their scope; problably because of different coatings for their lences: japan scopes are known for neutral colours, some producers are known for more bluish picture, some more yellowish (maybe this is better for mirage, just like car headlights for the fog?), some maybe more reddish, some maybe more greenish...

imho

 

[Denys]

@Ape_Factory
Thank you for your excellent answer; one never knows how people may react on fora (forums?).

I think what most people get worked up about is the thought that Super ED glass actually eliminates mirage. They are looking at it the wrong way. It's mainly that lesser glass gets more affected by mirage. I try to explain that Super ED glass retards the degradation brought on by the mirage compared to non-ED glass.

When I first realized this about 3 years ago, I hypothesized it this way. When the mirage manifests itself, it will mess up the IQ of a non-ED controlled glass faster and more thoroughly than the CA-free image generated by Super ED glass. This also explains why better glass "cuts trough" mirage better than cheaper glass because there are great attempts at controlling CA in better quality optics. These non-Super ED glass optics can control the dispersion of but a few wavelengths. ED glass, and especially Super ED glass (and best of all, pure fluorite crystal glass) control dispersion for all wavelengths to an increasing degree. But the IQ of these optics will definitely get messed up by the mirage; there's no escaping that.

The difference between a camera lens and a riflescope that I was thinking about is that in a camera lens all the optical work is done by the lens before it gets to the sensor. In a riflescope the equivalent sensor is at the first focal plane, everything after the FFP is the equivalent (broadly speaking) of cropping the picture from the sensor and blowing it up for viewing. The erector tube and the eyepiece do all that. Everything depends on the IQ at the FFP because after that, it only gets worse. If your FFP is as CA free as possible at the FFP, cropping and enlarging will yield better results to the eye.

The focal length of the objective lens group to the FFP is not that large, and Dawes' limit comes into play soon enough so you need the large objective lenses on these high magnification scopes. If you used a shorter telephoto on your camera and cropped/magnified the image and then used a loupe to look at the result, it might be a more apt comparison.