Pinewood
New York correspondent
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Very interesting thread by Lee. :t:
I look forward to Dennis's authoritative review.
Oh, no!
Happy bird watching,
Arthur
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Very interesting thread by Lee. :t:
I look forward to Dennis's authoritative review.
Like Dennis or not, he will step up to the plate and buy cutting edge glass that a lot of other only talk about. What he does with them after he buys them ?:-O
just noted that it's different then FL and HT, then whats the difference?
higher content of Calcium Fluorite?
Fluorite crystal is very difficult to work with as well, and expensive…
would be nice with some more info on the Ultra-FL glass,
Dobler says:
"The doublet is made from glass containing calcium fluorite, different from FL and HT but still supplied by Schott and it is very expensive and a challenge to work with as it can break more easily during manufacturing."
and some info from Takahashi web-site:
"..Other telescope manufacturers may claim that ED (Extra-low Dispersion) glass is the equivalent of fluorite or that their older designs will work as well. Unfortunately, they are not being honest. While ED and fluoro-crown lenses can achieve Abbe-coefficients approaching fluorite, they tend to absorb more light in the visible spectrum. This means that fluorite yields a brighter, higher contrast image. Leica, Zeiss, and Kowa have all gone to fluorite in their spotting scopes and telescopes to achieve the maximum performance levels their customers demand. Most of them previously used ED glass. Obviously, they know the difference between fluorite and ED. You will too. ...
"
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"To call lenses made of fluoro crown glass fluorite lenses is misleading and is a marketing attempt to sell on the back of the outstanding performance/ reputation of telescopes which used Calciumfluorit elements such as the Takahashi FS-102, FS-128, FS-150, the Vixen 102 and Calciumfluorit doublets of current production."
http://www.iceinspace.com.au/forum/archive/index.php/t-121155.html
Canon have used it in photographic optics for many decades. Nikon have started using it, along with their ED and super ED glasses. And the lenses are not even protected with rubber armour, so shock will be worse. This link is interesting:
http://cpn.canon-europe.com/content/education/infobank/lenses/fluorite_aspherical_and_ud_lenses.do
Canon claim a flourite element takes four times as long to grind, adding to the cost, although having only two objective elements will reduce costs a bit.
Very interesting thread by Lee. :t:
I look forward to Dennis's authoritative review.
Interesting that Nikon finally decided to use Fluorite in camera lenses. It seems to save a lot of weight in long telephoto lenses. Canons latest lenses are so much lighter than nikons corresponding ED-versions. Though the prices have become ridiculous on the new versions…
seems to be a lot of work though, making lenses:
http://www.youtube.com/results?search_query=canon+lens+production
wouldn't it be easier to sell sausages instead?
Like Dennis or not, he will step up to the plate and buy cutting edge glass that a lot of other only talk about. What he does with them after he buys them ?:-O
If the SF is by consensus of many credible opinions a true advancement over the latest SV, then I will more than likely buy one myself. It's all totaly speculatively at this point.
Hope to see the cutaway drawing soon!
Henry
VB
Every super market and butcher thinks it is easy to make sausages and so it is.
But it is not easy to make a really good one. :smoke:
Lee
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And it was interesting that the chosen level of distortion was arrived at not simply by calculation and theory, but aided greatly by empirical observations by people, and that this method brought SF so close to the line on your graph postulating an optimum distortion.
As always this is a compromise between the desired field flatness and the freedom from perceived rolling ball.
Lee
Hi BH
Its mostly speculative, thats true, but not entirely as I have been very fortunate to use SFs for a total of 22 hours or so and this is what I have based my comments on.
Let us know what you think when you try one out>
Lee
Hello Lee,
If I waive my daily cup of coffee, at a cafe; stop buying calvados or malt whisky; and avoid taking buses for less 2 km journeys, I should be able to afford the projected 8x32 SF, in early 2016. By then my FL will be a decade old. I hope that it may be worth the wait
Happy bird watching,
Arthur :hi:
Lee, thank you for the time and effort.
Your statements along with Mr Doblers as to the new SF are refreshing!
Thanks for sharing.
Bryce...
Hi Lee,
Just to clarify one point: The "optimum distortion" I had suggested was also based on empirical observations, namely the way volunteers perceived distorted Helmholtz checkerboards. The follow up calculations then simply tried to connect these observations with the amount of globe effect which might be perceived with the panning binocular.
I had to use this detour because it is far easier to construct Helmholtz checkerboards than binoculars with different amounts of distortion
Since Zeiss has now carried out globe-effect experiments without the detour via Helmholtz checkerboards, their data could be quite interesting, and I hope they will be published in the near future.
Thanks a lot,
Holger
Hi Lee
If the Cabellas that is coming locally this winter doesn't carry the SF, then my options for seeing a pair are very limited. I may be forced to suffer through with the SV.:-C3
Lee,
Awesome! Excellent question, and answers.
Ron
Lee,
Thanks for the interview. A good read. Interesting to hear the take of the product manager and gain some insight into their thinking.
Holger,
I share your thoughts on the "Absam ring" explanation. It would be nice to hear a bit more about it, since the field-stop explanation does not sound quite right.
Incidentally, I'm a bit annoyed by the "Absam" part of the term that has gained hold on these forums. It was probably coined by Brock in his crusade against the RB-effects of the Swarovisions, but the phenomenon it describes I first saw in Nikon's SE 10x42 which I got in 1996 and still have. It has very good edge of field sharpness, but a little bit inwards from the edge the sharpness falls off before increasing again, very much like in the Swarovisions. So, for historical correctness, credit should be given to the inventors of this anomaly and it should be called the "SE ring," unless an even earlier precedent is found. I do not know if this effect is equally visible in the 8x32 SE, since that model I have not thoroughly tested or viewed with.
Kimmo
As for the "Absam" ring, I agree it's a terrible term which means nothing to anyone much removed from this forum. Some descriptive term would be better. I've also seen it in other binoculars, including the SE. I suspect that the "apertures within the optical system" referred to by Herr Dobler are simply the prism apertures that introduce off axis vignetting of the objective light cone. That vignetting has been used as a way to reduce off-axis aberrations in binoculars since the very start. The downside is that it also reduces brightness toward the field edge as the surface area of off-axis exit pupils shrinks near the edge. IMO, the "Absam" ring is the area where off-axis aberrations just start to build and just before vignetting begins to become effective at reducing the aberrations. Increasing the vignetting to completely eliminate the soft ring would not be desirable in most cases because then areas near the edge of the field would become noticeably dim.
Hope to see the cutaway drawing soon!
Henry