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Where premium quality meets exceptional value. ZEISS Conquest HDX.

Why are Zeiss so sharp on-axis compared to other binoculars? (1 Viewer)

The SF was designed to have a more rearward balance than is typical with binoculars,
what Zeiss refers to as the Ergobalance Concept.

So the optical design, including the choice of prisms, was done with that in mind:

HT vs SF.jpg
HT x42 on left, SF x42 on right.

The images are from a 60 page brochure about the SF from 2015.
For more see: Zeiss Victory SF and HT - technical data, diagrams, cutaway views and more


John
 
The SF was designed to have a more rearward balance than is typical with binoculars,
what Zeiss refers to as the Ergobalance Concept.

So the optical design, including the choice of prisms, was done with that in mind:

View attachment 1598880
HT x42 on left, SF x42 on right.

The images are from a 60 page brochure about the SF from 2015.
For more see: Zeiss Victory SF and HT - technical data, diagrams, cutaway views and more


John
I never owned SF 42s but I have tried them and was amazed at the illusion they create of feeling much lighter than 800g.
In the hand they feel like a 32. It feels like some kind of trick. Zeiss worked some magic with these.
 
Zeiss SF 10x42 position of the focus wheel it is in the center of gravity of the binoculars, which is closer to the eyepieces, plays an important role in perfect ergonomics and stability. I took a very suggestive picture of how Zeiss SF can balance over the edge of "the abyss" by more than half of its length. Do not try this at home :)
SF 10x42  gravity.JPG
 
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The SF 10x42 is a great binocular and the rearward balance is great. I have a Zeiss SF 10x32 because I like the big 7.5 degree FOV, rearward balance and glare control. The SF 10x32 feels like many 10x30 binoculars because of the rearward balance. Zeiss went to an SP prism in the SF for compactness and the rearward balance design, but after having many AK prism binoculars including a Zeiss FL 7x42, I would have to agree with the AK prism camp that the AK prism does bring a certain kind of magic to the table.

There are without a doubt still advantages with the AK prism, and that is why so many manufacturers still use them when they aren't concerned about the compactness of the binocular. An AK prism binocular seems more transparent to me, similar to a porro and I believe it is because the AK prism has a more relaxed image because of the simpler optical train similar to a porro. The AK prism is also brighter and seems to have more contrast because of the higher 2% light transmission. Also, because of the increased offset of the objectives on an AK prism binocular, there is a slight increase in the 3D effect similar to a porro but not as dramatic.

An AK prism is more 'relaxed'. It only has 4 reflections, and it doesn't need a reflective coating because it doesn't have a surface without TIR. An SP prism has 6 reflections, and one of the non TIR surfaces needs a mirror coating. Also, there are three surfaces that perform two functions, both transmission and reflection, and consequently require compromised coatings to address the conflicting functions. (John A. Roberts)

I think if you are concerned about just optical performance instead of the design parameters of the binocular like weight and size, the bigger AK prism will without a doubt outperform the more compact SP prism in most cases. If Zeiss had not cared about the compactness, weight rearward design of the SF, an AK prism would have outperformed the SP prism they used.

For those of you that think an SP prism is the equal of an AK prism, ponder this question. When Zeiss has the room to use an AK, why do you think they use an AK prism instead of an SP? In all Zeiss's bigger binoculars like the 56mm and even the HT 8x42 and FL 8x42 they have used an AK prism. The answer is because they are more efficient and brighter, and have other advantages as well. If they had had room in the SF 10x42 for an AK, they would have used one also.
 
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So, can anyone easily list the binos still using AK (current or recent production)?
As the fan of the AK prism, I have had or seen some AK binos

AK prism I have seen (recent & still produced)

Alpen teton EDHD 10x42

nice build quality but eyecup and eyerelif is bit short for it's price
indeed bright. brighter then CHD par with TFL.
but too strong CA and edge blurriness...
only recommend for night time hunters.


Bushnell forge 15x56

failure of AK prism. I agree with a low transmission result that allbino give. and not that good CA and colorfidelity compared to 10x42 forge

Zeiss conquest HD 8x56

longer and heavier then I expected. superb central sharpness that easily exceed steiner nighthunter 8x56. (though brightness and color fidelity bit below)

Sightron SV & Vortex razor UHD 8x42

good but didn't reached the optical perfomance of SLC & HT

(I'm planning to wright english review about these . but recently I have too much Korean reviews to write before.)

Zeiss TFL 7x42

optically best 7x42 I've seen.
though I didn't like it's mintish coloring and pincusion distortion

Zeiss TFL 10x56

disappointing ergonomics (Too much weight on the objective side), color renedition. but top of the pack CA, Glare control.
top sharpness & resolution I've seen between every10 Power Zeiss.

Swaro SLC 10 & 15 x56

best AK overall optically. central - edge sharpness, CA & Distortion control
but suffer from glare & ghost

Zeiss HT 8&10 42mm, 10x54

Brightest (and most expensive) AK for it's size.

1000254784.jpg
1000254785.jpg
1000254782.jpg
1000254783.jpg
can't find a photo of Zeiss CHD 8x56 and TFL 7x42


all of them has reviews on Korean bino forum and I can upload hear in english form if I have some time.
(Alpen teton already have review on this forum)
but before then, I can give you brief information of the bino.

my favorite AK is Victory HT series.
they are not prefect bino like Swarovski but they still roams the market in terms of brightness. and that's why AK prisms are made for.
so I think HT is the best binocular to use it's AK prisms to it's maximum.

other AK prism I heard about but haven't seen yet

DD optics pirschler / GPO passion 56 / Maven b2 / Sig zulu 9&10 / Conquest HDX 56 / Nikon WX...
 
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Nice pictures and comparisons! It is helpful to see the size comparisons of the different binoculars and the varying objective offsets of the AK prisms.
 
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Here is a short list of binoculars with AK prisms from Cloudy Night's (Pinac)


  • DDoptics, Pirschler 8x56 (identical with Vixen New Foresta, see below)
  • DDoptics, Nachtfalke 10x60 / 12x60
  • Docter 8x56 ED/OH
  • Optolyth Royal 8x56 / 10x56
  • Optolyth Royal 9x63 / 15x63
  • SIG-Sauer Zulu 9 (9x45 / 11x45)
  • Swarovski SLC 8x56 / 10x56 / 15x56
  • Vixen New Foresta 8x56 (identical with DDoptics ,Pirschler)
  • Vortex Razor UHD
  • Zeiss Conquest 8x50 / 10x50 / 8x56 / 10x56 (out of production)
  • Zeiss Conquest HD 8x56 / 10x56 / 15x56
  • Zeiss Conquest HDX 8x56/ 10x56/ 15x56
  • Zeiss Dialyt 8x56
  • Zeiss Victory FL 7x42/ 8x42
  • Zeiss Victory Fl 8x56 / 10x56 (out of production)
  • Zeiss Victory HT 8x42 / 10x42
  • Zeiss Victory HT 8x54 / 10x54
  • Nikon WX 7x50 IF/ 10x50 IF
  • Maven B.2/ B.5
 
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So the Nikon WX uses AK's
Says it all then💁‍♂️
Yes, I heard the AK prism was the only prism that would handle that wide of a FOV, and the WX's already have a lot of glass in them absorbing light, so an AK helps because it is more efficient and has higher transmission. They don't have to worry about compactness, so they went with the best prism, the AK. Zeiss always did use AK prisms in their bigger binoculars when they have room, and they still do.

 
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The SF was designed to have a more rearward balance than is typical with binoculars, what Zeiss refers to as the Ergobalance Concept.
Given the complexity of optical design itself, it amazes me that one can still play such games with the physical arrangement of elements.

I find the explanation in the brochure quite contradictory: having the center of gravity a bit further forward on HT correlates naturally with holding it further forward, as induced by the focuser position (image 1 below). But then when they present the Ergobalance Concept, the victim is shown suffering from front-heaviness because he's holding HT further back, a hold in which focusing would be difficult or impossible (image 2). This is not convincing.

I never owned SF 42s but I have tried them and was amazed at the illusion they create of feeling much lighter
This has always seemed an illusion to me, resulting from SF's greater size. Larger objects with similar weight are less dense, not lighter.
 

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