More contrast with ED scopes? (1 Viewer)

[John goshawk]

If two spotting scopes have identical specifications but one is ED, does the ED scope have better contrast?
I understand what ED glass does regarding chromatic aberration, but was wondering if it effects contrast as well and if so how.

Many thanks John

 

[John goshawk]

Someone surely?

 

[dwatsonbirder]

John, I have no technical knowledge on such things, but whilst you await a better reply here are some considerations in short;

i) it will depend upon the type of glass employed, and the manufacturing tolerances used. Cheap mass produced ED glass may not yield the same results as high quality standard glass.
ii) the design of the scope (e.g. focal length) may affect the contrast, perhaps more noticeable between two otherwise identical models in a compact form, and less so in something like a draw tube design.
iii) same variation between identical models made to the same specification can vary.

In short, there may be some obvious differences between a low end ED and non-ED version of the same scope, whilst the differences may be less obvious in a higher end unit. There are cherries and lemons of pretty much any production run, so I suspect there isn't a set answer.

 

[Nethero]

If two spotting scopes have identical specifications but one is ED, does the ED scope have better contrast?
I understand what ED glass does regarding chromatic aberration, but was wondering if it effects contrast as well and if so how.

Many thanks John

My experience is based off of Nikon ED III 60mm v. Nikon III 60mm (non ED) & a Swarovski ATS 65mm, one with ED glass (HD) and one without.

The ED scopes handle color fringing much better, leading to cleaner line/edge definition, thus providing better contrast. Also, the ED scopes appear to show better color depth/saturation/look less washed out. Whether this is another function of chromatic aberration’s being controlled, I do not know.

 

[Ratal]

If two spotting scopes have identical specifications but one is ED, does the ED scope have better contrast?
I understand what ED glass does regarding chromatic aberration, but was wondering if it effects contrast as well and if so how.

Many thanks John

Yes. Vastly better.

 

[Hermann]

My experience is based off of Nikon ED III 60mm v. Nikon III 60mm (non ED) ...

Same experience here, in my case the Nikon EDII and the Nikon II (non ED). The difference is quite obvious, not just at high magnifications, but also at low magnifications (20x). I also had a Leica Apo-Televid 77 and a Televid 77 long ago. Same story.

The ED scopes handle color fringing much better, leading to cleaner line/edge definition, thus providing better contrast. Also, the ED scopes appear to show better color depth/saturation/look less washed out. Whether this is another function of chromatic aberration’s being controlled, I do not know.

What he said.

Hermann

 

[John goshawk]

Cheers folks. Just seen a similar thread on cloudynights. Technical stuff!
John

 

[Hermann]

John, I have no technical knowledge on such things, but whilst you await a better reply here are some considerations in short;

i) it will depend upon the type of glass employed, and the manufacturing tolerances used. Cheap mass produced ED glass may not yield the same results as high quality standard glass.

Too true. In cheap scopes you often won't even know if they really used ED glass (and what type), everyone can label their scopes "ED". As a result a good, "normal" scope without ED glass may be better than a cheap scope that claims to incorporate ED glass.

ii) the design of the scope (e.g. focal length) may affect the contrast, perhaps more noticeable between two otherwise identical models in a compact form, and less so in something like a draw tube design.

Yes, also true, at least to some extent. However, there aren't many birding scopes with long focal length on the market nowadays.

iii) same variation between identical models made to the same specification can vary.

Yep. Sample variation is a big problem, even with the top manufacturers.

In short: Buy a scope with ED glass from a good manufacturer. And test it before you put your money on the table.

Hermann

 

[John goshawk]

Great answers, thanks.

 

[PYRTLE]

I think Nikon first used the term ED as on their Fieldscope series loosely standing for "extra dispersion" glass used in manufacturing their lenses and objectives. Kowa used the term Prominar to denote something similar for scopes using Fluorite. Swarovski incorporated HD, Higher Definition, for their superior instruments and Leica the term APO in relation to apochromatic lens figuration. This was fine and worked well for some time before the floodgates opened and nearly every brand started using some form of ED / HD labelling, suggesting their particular model was on a par with the likes of those above mentioned high spec companies..... no Siree.
Bit like the motor industry where every range had a GT version..... eg Ford Escort GT v Ford GT40 - very different animals.
As Hermann has intimated an ED notation on a mass produced €400 " far Eastern manufactured " scope isn't going to improve performance as well as say an Austrian €3500 instrument.
It's the old adage that, "You get what you pay for".
Hope this makes some sense.

 

[John goshawk]

Very interesting, thanks. Ive had a few 'ED' scopes over the years. My favourite is my Opticron HD66. Worth noting it was much cheaper than my previous Kowa or Nikon. A bit heavy - but it's a keeper.
John

 

[Chris Pringle]

Yes, ED glass would indeed render better color contrast, definition and CA. It’s not a gimmick. Furthermore, I think that ED glass/optics manufactured in the Far East has been vastly improved over the last five years or so. ED glass is also used in refractor telescopes for astronomy and the most recent iterations are of superior quality for visual purposes. Buying binoculars from reputable sources based in the U.S. or Europe - that perform their internal Q/C by testing each unit before shipping it to the end user - greatly reduces the chances of receiving a suboptimal unit. In the world of optics, ED glass is currently considered a mid-level glass that factories in the Far East can now manufacture/figure very well.

There is a higher category of glass called Super Low Dispersion (SD) which is still very tricky to manufacture and to figure. It is mostly used on scientific and astrophotography applications requiring incredible optical accuracy. The world leaders for the manufacturing of that type of glass are Ohara (USA) and Hoya (Japan), but you better believe it that there has to be some factory in China already working on their own version. I suspect the reasons why this super-duper (SD) glass technology has not trickled down to binoculars are most likely due to pricing and because most terrestrial visual applications don’t need such tight tolerances. But I am certain that’s the next frontier in binoculars glass. It’s basically the difference between HD and Ultra HD.

European or Japanese companies do continue to have an advantage over Chinese-made binoculars on the execution of the entire package - quality and ergonomics of the shell that feel precious in your hands and on your face, enviable quality of the mechanics and components for smooth and accurate focusing, eyecup adjustment, etc. Let’s say that for the average user, you can get very good quality (score of 4.3-4.5 out of 5) from Chinese binoculars or scopes in the range of $300-$500 USD. But the jump to excellence (4.7 to 5.0 score) from Japanese or European brands will cost you anywhere from 4 to 10 times as much.

 

[John goshawk]

Yes, I would agree fully with this.

Thanks John

 

[Hermann]

Yes, ED glass would indeed render better color contrast, definition and CA. It’s not a gimmick. Furthermore, I think that ED glass/optics manufactured in the Far East has been vastly improved over the last five years or so. ED glass is also used in refractor telescopes for astronomy and the most recent iterations are of superior quality for visual purposes. Buying binoculars from reputable sources based in the U.S. or Europe - that perform their internal Q/C by testing each unit before shipping it to the end user - greatly reduces the chances of receiving a suboptimal unit. In the world of optics, ED glass is currently considered a mid-level glass that factories in the Far East can now manufacture/figure very well.

But then there's NO universally accepted definition of "ED glass". Not AFAIK. In the end you have to rely on the manufacturers' claims.

There is a higher category of glass called Super Low Dispersion (SD) which is still very tricky to manufacture and to figure. It is mostly used on scientific and astrophotography applications requiring incredible optical accuracy. The world leaders for the manufacturing of that type of glass are Ohara (USA) and Hoya (Japan), but you better believe it that there has to be some factory in China already working on their own version.

You forgot to mention Schott (Germany).

European or Japanese companies do continue to have an advantage over Chinese-made binoculars on the execution of the entire package - quality and ergonomics of the shell that feel precious in your hands and on your face, enviable quality of the mechanics and components for smooth and accurate focusing, eyecup adjustment, etc.

In an ideal world - yes. However, over the past 10-15 years there have been quite a lot of problems with European and Japanese ´manufacturers relasing binoculars that were clearly not ready for prime time. In other words: Bananaware.

Let’s say that for the average user, you can get very good quality (score of 4.3-4.5 out of 5) from Chinese binoculars or scopes in the range of $300-$500 USD. But the jump to excellence (4.7 to 5.0 score) from Japanese or European brands will cost you anywhere from 4 to 10 times as much.

Agreed.

Hermann

 

[jring]

You forgot to mention Schott (Germany).

And Hikari (aka Nikon) and most importantly, CDGM... which would be "that factory in China"...

As for why to use ED glass - super ast refractors like our spotters tend to get soft even on axis beyond 40x or so due longitudinal chromatic aberration. The yellow/purple fringing mainly seen off axis is the other kind - transversal CA.

The usual definition of ED glass is Abbe Numbers above 80 or so... see Figure 148 on REFRACTING TELESCOPE OBJECTIVE: SEMI-APO AND APO OBJECTIVES

Joachim

 

[tenex]

There is a higher category of glass called Super Low Dispersion (SD) which is still very tricky to manufacture and to figure. It is mostly used on scientific and astrophotography applications requiring incredible optical accuracy...

SD glass (and also "anomalous partial dispersion") is used in some long camera lenses today. I wonder whether anyone would notice the difference visually in a binocular. Maybe a spotting scope.

 

[beacon hill]

At our optics weekends , bear in mind a number of my customers are looking at bins and spotters for the 1st
time, not knowing what any of the numbers or words mean. We all had to start somewhere , right ?,
and have not clicked on a link in advance to research.

So without insulting intelligence I stick to practical lessons. Remember these are people starting out
that have no idea what 8x or 42mm means.
When comparing a like for like price / spec ED vs non ED option, I ask them to look at a white object.
Using a clothes wash analogy I ask them if the whites seem whiter with the ED and maybe a creamy white
with the non ED. Also the reverse with dark areas. So this helps explain contrast for a complete beginner.

But I also see the post has included CA.
For this, my practical demonstration is the lamp post test or if lucky at the park a Swan against a dark background.
No need to explain that demo any further.

Some may shoot me down for my demo techniques. But you would be amazed how many customers have mentioned
that they would not have found any of the above by searching on-line and my advice helped them understand
in practical terms what all the terminology means.

But yes, I also get customers with a set of Alpha bins, looking for a second set to keep in the car.
For more experienced users there is no need to demo anything as they can do all the QC themselves.

 

[John goshawk]

Very good. Is the chroma aberration not very local/fringing.How does it spread throughout the entire white area.
This was actually the point of my question.
Thanks John

 

[Nethero]

Very good. Is the chroma aberration not very local/fringing.How does it spread throughout the entire white area.
This was actually the point of my question.
Thanks John

CA is localized in that it shows itself on the edges of defined objects (branch or bird against the sky), which in turn muddies the definition of the object.

I think @beacon hill l was saying that ED glass overall has better color rendition, similar to me saying non-ED glass looks more washed out.

 

[Tringa45]

All else being equal there is no perceptible difference in surface colour rendition between ED and non-ED glass.
As Joachim pointed out in post #15 ED glass can reduce colour fringing on axis (longitudinal CA) caused by the objective.
Lateral colour (at the field edge) is caused by the eyepiece and is impossible to correct to imperceptible levels because of the high angular magnifications and consequent dispersion.

John