An interview with Gerold Dobler, leader of the SF design team (1 Viewer)

Pinewood · Nov 2, 2014

Leif said:
...
Very interesting thread by Lee. :t:

I look forward to Dennis's authoritative review.

Oh, no!

Happy bird watching,
Arthur

etudiant · Nov 2, 2014

bh46118 said:
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

That is exactly the question.
Dennis, God bless him, does step up to the plate and buy. He normally then offers very positive opinions about the item. However, he usually then sells and his real feelings only emerge subsequently. So to get the true scoop from Dennis takes a while.

henry link · Nov 2, 2014

Vespobuteo said:
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. ...
"
---

"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

Vespobuteo,

In your last link scroll down to the comments by "bratislav". They have the best information about how Fluorite compares to FPL-53 and equivalent glass types for use in telescopes.

I just looked at the 2014 Schott catalogue. There's only one glass in there with an Abbe# above 70: FK-51 at Abbe 84.5. That's not very close to Fluorite or the glass equivalents of Fluorite at Abbe 95. Schott has produced lower dispersion fluor-crown glasses in the past like FK-54, 90.7 and FK-56 (or maybe it was FK-57?), which, if my memory is correct, was a Fluorite equivalent at 95. Perhaps a small run of one of those was done for the SF objective. If someone at Zeiss would just come out and tell us the Abbe# of the glass in the SF all the speculation could end. I was happy to see the SF objective honestly referred to as an "achromatic doublet". There have been too many false claims of APO performance from the fast objectives of ED binoculars.

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

Troubador · Nov 2, 2014

Leif said:
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.

Hi Leif

Great to hear from you, and thank you for your kind words.

I think these sorts of lenses are more difficult and therefore more costly to process in every way.

Lee

Troubador · Nov 2, 2014

Vespobuteo said:
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?

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

Troubador · Nov 2, 2014

bh46118 said:
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.

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

Troubador · Nov 2, 2014

henry link said:
Hope to see the cutaway drawing soon!

Henry

Hi Henry

Thanks for your comments about the apertures, a very useful complement to Herr Doblers answer in the interview.

I expect to get the cutaway drawing tomorrow or Tuesday and will post it asap.

Lee

Pinewood · Nov 2, 2014

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:

Vespobuteo · Nov 2, 2014

Troubador said:
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

so true!
bratwurst, beer and binoculars,
they are all about science, intuition and art,
and we know where the best ones come from,
B

stereotruckdriver · Nov 2, 2014

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...

Holger Merlitz · Nov 3, 2014

Troubador said:
...

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 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

bh46118 · Nov 3, 2014

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

Troubador said:
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

ronh · Nov 3, 2014

Lee,

Awesome! Excellent question, and answers.

Ron

Troubador · Nov 3, 2014

Pinewood said:
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:

Art

I kept my FL for 9 years so you are definitely coming up to the time to look around at new possibilities :t:

Lee

Troubador · Nov 3, 2014

stereotruckdriver said:
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...

Thank you kindly Bryce, nice of you to stop by and say so.

Lee

Troubador · Nov 3, 2014

Holger Merlitz said:
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

Of course, Holger, I remember the checkerboards now, thanks for correcting my memory and understanding.

Lee

Troubador · Nov 3, 2014

bh46118 said:
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

BH

You poor fellow, I don't know how you manage to endure the burden of looking through that SV

but I am sure you will survive.

Lee

Troubador · Nov 3, 2014

ronh said:
Lee,

Awesome! Excellent question, and answers.

Ron

Whoa Ron, you got me blushing here........ thank you for your kind words.

It was great fun deciding on the questions and on how to put them to Herr Dobler in such a way that they were not excessively critical and did not demand information that was obviously still confidential, but did elicit the answers that we have all been looking for.

Herr Dobler understood immediately the idea that the interview was not to be like the recent video in which 'catalogue statements' were aired.

There was a little more freedom of discussion and disclosure possible because SF deliveries into the market place have just begun at a modest level which means that over the coming weeks and months anyone will be able to get an SF and take it apart to discover the internal layout. So the timing of the interview was critical in enabling the right level of openness.

Lee

Tobias Mennle · Nov 3, 2014

kabsetz said:
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

I see nothing like it in the SE 8x32, but I had a close look at the Absam/SE ring in the Swarovision 8x32. So it´s more critical in 10x models?

Thanks Lee, great interview.

Tobias Mennle · Nov 3, 2014

henry link said:
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

This is a brilliant explanation of the Absam ring (love that term), but I don´t think there is much vignetting to be seen.

An interview with Gerold Dobler, leader of the SF design team (1 Viewer)

New York correspondent

Registered User

Well-known member

Moderator

Moderator

Moderator

Moderator

New York correspondent

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Moderator

Moderator

Moderator

Moderator

Moderator

Well-known member

Well-known member

Similar threads

Users who are viewing this thread