Curtis Croulet
Well-known member
Jonathan B. said:
I have seen CA in my FL. I was quite startled to discover it, since I had previously considered CA in binoculars to be a non-issue for me.
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Can a Non-Fluorite lens binocular compete with a Fluorite lens binocular? (1 Viewer)
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I have seen CA in my FL. I was quite startled to discover it, since I had previously considered CA in binoculars to be a non-issue for me.
xenophobe
Well-known member
AlanFrench said:
Hi Alan, I understood your point. I'm also not disrespectful of any APO-type glass out there, but I question how much more clarity you'll get out of my 7x42 Dialyts or my 10x42 Ultravids if someone were to replace a single lens with fluoride, CaF or ED glass. They're about as bright and sharp as you're going to get, IMO. The only thing I believe that can be done better is eliminating the CA, which my 7x42's is pretty near non-existant, and only an issue in the outermost 10% of my Ultravids, neither of which distract from their amazing views. Can it be done better? Sure. Considerably better? I don't think so.
I have yet to try a pair of FLs, so maybe I'll eat my words and a lot of humble pie when I do. Certainly, if I thought CA were a problem, I would be really intent on finding a pair to view through. As it stands, I've compared my bins to many others out there and know they're at the top of their game.
I'm not questioning the fact if they should be included in higher powered optics, telephotos, spotting scopes, or even high powered big bins, as its very apparent that they do.
An extra low-dispersion element doesn't just reduce CA, it also corrects for spherical aberration. Both effects will improve the contrast and sharpness.
The need for low dispersion elements in 35mm camera lenses is accepted and is not a gimmick. The general opinion, from what I have read, is that lenses with ED glass tend to have improved contrast and less CA than the vanilla equivalents. (I have owned ED lenses, but had nothing to compare directly.) However there are cases where manufacturers produce ED and non-ED variants. Nikon have two 70-300 lenses, one ED, one vanilla. The ED is noticeably better. I think the biggest improvement is at the long end. ED glass used to be common only in long lenses - 400mm and greater - but now it is being used in shorter focal lengths, and especially in wide zooms. I guess it allows the designer greater freedom. My Nikon 28mm AIS F2.8 lens has no ED elements and is superb, but a zoom is no doubt more demanding.
Interestingly the new Canon 10x40 IS binocular includes several ED elements (described as UD IIRC).
I too have seen some CA through my Zeiss 8x42 FL, but to my eyes it is minor.
Leif
The need for low dispersion elements in 35mm camera lenses is accepted and is not a gimmick. The general opinion, from what I have read, is that lenses with ED glass tend to have improved contrast and less CA than the vanilla equivalents. (I have owned ED lenses, but had nothing to compare directly.) However there are cases where manufacturers produce ED and non-ED variants. Nikon have two 70-300 lenses, one ED, one vanilla. The ED is noticeably better. I think the biggest improvement is at the long end. ED glass used to be common only in long lenses - 400mm and greater - but now it is being used in shorter focal lengths, and especially in wide zooms. I guess it allows the designer greater freedom. My Nikon 28mm AIS F2.8 lens has no ED elements and is superb, but a zoom is no doubt more demanding.
Interestingly the new Canon 10x40 IS binocular includes several ED elements (described as UD IIRC).
I too have seen some CA through my Zeiss 8x42 FL, but to my eyes it is minor.
Leif
BTW The next big thing is a super-light 10x40 IS DO binocular from Canon. The DO (diffractive optics) objective allow improved correction for CA and shorter tubes for a more compact light instrument. Well, actually this is nonsense made up by me, but if money was no object, then this might well be reality rather than fiction.
Leif
Leif
AlanFrench
Well-known member
Leif said:
Leif,
I do not believe ED glass provides any ability to correct SA beyond what can be obtained in a traditional achromat. At least one ED doublet I am familiar with, which provides superb color correction, has a large amount of spherical aberration and must be hand aspherized to provide good performance.
Clear skies, Alan
xenophobe
Well-known member
Dennis,
Apparently the Ultravids use Fluorite glass as well:
http://www.birdforum.net/showpost.php?p=403733&postcount=4
Apparently the Ultravids use Fluorite glass as well:
http://www.birdforum.net/showpost.php?p=403733&postcount=4
I read the post referred to above, but remain unconvinced that the Ultravids would utilize fluorite lenses or other ED-type materials. Granted, the source quoted sounds reliable, but firstly, I have a very hard time believing that Leica marketing department would have failed to toute this feature (which has not been mentioned in any of the brochures, press releases etc. I have ever seen). Secondly, the performance of the Ultravids with respect to CA gives no reason to suspect that something out of the ordinary would lurk in the depths of the design.
Kimmo
Kimmo
That was my post referred to in the thread. Unfortunately, the article didn't mention WHICH lens element is fluorite in the Leica Ultravids--it could be one of the elements in the eyepiece rather than part of the objective. The information came from Dr. Ulrich Ehmes who is the manager of the Leica Sport Optics line, and he said, "Glass types that contain fluorite have been used in the production of Ultravid binoculars and Televid spotting scopes..." However, the sport optic brochures only refer to the fluorite in the spotting scopes. Hard to know.
I don't know why Leica marketing doesn't mention the Fluorite if it is there. This wouldn't be the first time, though. When the Trinovids came out you had to look pretty hard to find out that they were "phase coated." That was the new, hot technology then, and Leica failed to mention it in almost all of the marketing literature.
Several posters have referred to the major advantage of the Zeiss FL's as the Abbe/Koenig prisms which allow total internal reflection within the prism and thus didn't require a silvered or aluminized surface. This is why Zeiss binos traditionally had a brighter image than their competitors. It's also why they were ususally physically longer than their competitors, since the AK prism takes up more space. Modern dialectic mirrors have improved throughput on the Ultravids (and presumably others as well), so this advantage has disappeared.
Whatever the glass used, clearly the high end binos get near 100% throughput with very high resolution. Yes, there is some CR left, but it is pretty negligible at typical binocular magnifications.
- Jared Willson :t:
I don't know why Leica marketing doesn't mention the Fluorite if it is there. This wouldn't be the first time, though. When the Trinovids came out you had to look pretty hard to find out that they were "phase coated." That was the new, hot technology then, and Leica failed to mention it in almost all of the marketing literature.
Several posters have referred to the major advantage of the Zeiss FL's as the Abbe/Koenig prisms which allow total internal reflection within the prism and thus didn't require a silvered or aluminized surface. This is why Zeiss binos traditionally had a brighter image than their competitors. It's also why they were ususally physically longer than their competitors, since the AK prism takes up more space. Modern dialectic mirrors have improved throughput on the Ultravids (and presumably others as well), so this advantage has disappeared.
Whatever the glass used, clearly the high end binos get near 100% throughput with very high resolution. Yes, there is some CR left, but it is pretty negligible at typical binocular magnifications.
- Jared Willson :t:
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Humboldt Jim
Well-known member
[email protected] said:
Absoltely! They can and do. Flourite and other ED lenses are merely able to refract light at the same angle with less chromatic aberation (CA) or refract it more with the same CA, or somewhere in between. This allows for more compact optics and/or less CA in the image, other things being equal. Which of course, never are.
I think the ED glass in my Pentax 65ed scope allows for a more compact design with no apparent CA except in the most extreme circumstances. By my rough calculations it is a bit smaller than a scaled down 80. The same principles apply to binoculars.
A "blind" comparison between similar flourite and non-flourite optics would be interesting.
jwillson said:
Perhaps surprisingly there is significant variation in light transmission between the diffferent top ends bins. A recent thread on BF listed some measured values, though I'm not sure where it is. The best - I think Zeiss was top - transmitted well over 90%, whereas some were closer to 80%. The Leica Ultravid was quite high too. One of the lowest, if not the lowest, of the top bins IIRC was the Swarovski EL. These are peak values so they do not tell us about average transmission over the visible spectrum. Whether or not you consider a difference of 10% or greater to be significant is another issue. I believe the Nikon SE range have ~96% transmission, though that is from memory, so I would take that figure with a pinch of salt.
Leif
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jwillson said:
Interesting. Leica mention Fluorite in their brochures for spotting scopes (as well as Fluoride) when the real term should be Fluoride and not Fluorite.
I am pretty certain that if Leica had Fluoride lens in their binoculars they would have mentioned it before now. I do not believe that Leica use fluoride glass in their bins.
In answer to the first question (and not getting involoved with all the technical details) - yes non-FL bins can compete.
I work for an optics retailer and the Zeiss FL has caused a bit of a stir, they are excellent binoculars and certainly are selling better than the previous Zeiss bins. However ultravids, ELs and HGs are still selling very well. Zeiss are definitely increasing there market share, but I doubt that Leica and Swaro are getting too worried, both are still very popular.
I recently changed my bins and compared all the top end models before deciding what to go for. The Zeiss FL's were very impressive and unlike when I look a couple of years ago Zeiss was a real option. In the end I went for the ultravids, though the Zeiss would have been a close second, my complaint about them isn't with the optics, but the build, they just felt wrong in the hand.
I work for an optics retailer and the Zeiss FL has caused a bit of a stir, they are excellent binoculars and certainly are selling better than the previous Zeiss bins. However ultravids, ELs and HGs are still selling very well. Zeiss are definitely increasing there market share, but I doubt that Leica and Swaro are getting too worried, both are still very popular.
I recently changed my bins and compared all the top end models before deciding what to go for. The Zeiss FL's were very impressive and unlike when I look a couple of years ago Zeiss was a real option. In the end I went for the ultravids, though the Zeiss would have been a close second, my complaint about them isn't with the optics, but the build, they just felt wrong in the hand.
Eye's response to light
Keep in mind that the eye's response to light is logarithmic, so a 10% difference in light transmission is actually very small in terms of perceived brightness. I'm not certain it would even be detectable. You may have known this, of course, but I wouldn't want someone looking at a 90% transmission vs. a 95% transmission and thinking, "Gosh, that's a pretty big difference in brightness!"
- Jared
Leif said:
Keep in mind that the eye's response to light is logarithmic, so a 10% difference in light transmission is actually very small in terms of perceived brightness. I'm not certain it would even be detectable. You may have known this, of course, but I wouldn't want someone looking at a 90% transmission vs. a 95% transmission and thinking, "Gosh, that's a pretty big difference in brightness!"
- Jared
CDK said:
You're right that Fluorite is mentioned in the spotting scope brochures. Further, the scopes with fluorite elements are all listed as APO. This isn't the case with any of the Ultravid binoculars. My information on the Ultravids came from a quote in the current issue of Leica World:
Dr. Ulrich Ehmes who is the manager of the Leica Sport Optics line said, "Glass types that contain fluorite have been used in the production of Ultravid binoculars and Televid spotting scopes..."
Maybe he made a mistake? Or maybe they don't mention it since the binos still aren't technically APO? Or maybe they don't mention it since only prototypes had the fluorite? Or maybe they don't mention it for some other reason altogether... Your guess is as good as mine.
- Jared
jwillson said:
Yes, I have difficulty seeing small differences in brightness.
Anyway, in daylight the eye's pupil is dilated to typically 2mm hence it is not using all of the light gathering power of the binocular (assuming roughly the same dilation with and without the bins). I presume that given two binoculars with different transmission, the eye will simply open up a bit more when viewing with the 'lesser' instrument.
I think what a lot of us consider to be differences in brightness, are really differences in contrast. To my eyes there is quite a range of variation in contrast between binoculars, even premium ones. Contrast does not seem to be directly linked to transmission, though they are clearly closely tied.
Leif
Robert Ellis
Larus marinus
BTW, where has that denco gone?
To oversimplify this issue ED glass was first used to minimize CA in short focal length Astronomical Refracting Telescopes. As a result refracting telescopes lengths and weights were markedly diminished; their portability increased and it became possible to take great astro-photos using much shorter guided exprosures. The technology has benefited binoculars but the results obtained aren't nearly as spectacular as they are in astronomy.
Robert Ellis
Larus marinus
ceasar said:
Yes. I remember saying something to that effect already. FL HAD to be used in these Zeisses because the AK prisms bring more light through, more light means more visible CA, more CA means if Zeiss wants to compete they will ditch the Victory 2 and introduce its replacement/fix in the FL.
Robert Ellis said:
Yes I am told that the Victory has more CA than average. However I don't believe there is any connection between CA and light transmission. It might be that because the AK prisms are long compared with SP ones, Zeiss use faster objectives to keep the length manageable (though still long compared with others). That means more CA unless improved objectives are used c.f the FL. However, IMO the FL do have less CA than competing instruments, so on that front they are not merely catching up with the competition.
Leif
