Why did Zeiss ditch the abbe koenig prism in the Victory SF? (1 Viewer)

Just wondering about this.

Is it the case that Schmidt-Pecan prism are now close enough in light transmission that there is no reason to stick to the less compact abbe koenig design? (and if that is so, how come we never see Leica or Swarovski tout the improvements of their SP prisms?)

Or is it the case that the use of field flattener elements and the other redesigns that improved the ergonomic handling of the Victory SF prevented them from sticking to the Abbe Koenig prism?

Not an expert, but I guess SP was needed to get widge angle, flat field at light weight. The SP is still behind in transmission, I think Zeiss said 92 % for the SF and up to over 95% or so for the HT...

Saturninus said:

Just wondering about this.

Is it the case that Schmidt-Pecan prism are now close enough in light transmission that there is no reason to stick to the less compact abbe koenig design? (and if that is so, how come we never see Leica or Swarovski tout the improvements of their SP prisms?)

Or is it the case that the use of field flattener elements and the other redesigns that improved the ergonomic handling of the Victory SF prevented them from sticking to the Abbe Koenig prism?

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The SP configuration is rather compact and less heavy than the AK. Note that Zeiss has used SP prisms in their 42mm Victory FL, too, and the SF follows the same strategy. Regarding transmission/resolution, I guess the AK has still got the advantage (though a tiny one). The Zeiss SF is a compromise, like any other design. It wants high quality optics, combined with a low weight. SP prisms and the doublet objectives certainly imply minor compromises with the image quality, but they also guaranty a low weight.

Cheers,
Holger

Holger Merlitz said:

The SP configuration is rather compact and less heavy than the AK. Note that Zeiss has used SP prisms in their 42mm Victory FL, too, and the SF follows the same strategy. Regarding transmission/resolution, I guess the AK has still got the advantage (though a tiny one). The Zeiss SF is a compromise, like any other design. It wants high quality optics, combined with a low weight. SP prisms and the doublet objectives certainly imply minor compromises with the image quality, but they also guaranty a low weight.

Cheers,
Holger

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I think you mean 32 mm FL's.....

Like Holger says, the possible image quality improvements offered by A-K prisms over S-P prisms are very slight even theoretically, in an optimal optical execution. In practice, none of even the very best binocular models by the very best manufacturers are built to tight enough tolerances that the benefits of the A-K prisms would ever be visible, as they would be hidden under spherical aberration, coma, astigmatism and chromatic aberration that the manufacturers allow to remain in the binocular image to varying degrees since they maintain that it does not matter. The only advantage that the A-K prisms have that could be visible in real-life commercially available binoculars under some conditions and to very critical observers is the up to 3% advantage in light throughput, but even that is so minimal that it hardly matters, and would play second fiddle to almost any individual sample variation differences in the actual binoculars being compared.

So, in my view, it is eminently sensible to prefer S-P prisms if and when it allows making a more compact binocular with better ergonomics and weight distribution. It also makes sense to prefer A-K prisms if being able to credibly claim maximum light throughput in advertising to your target customers is more important than compactness, weight distribution and ergonomics.

Kimmo

Gerold Dobler's target of shifting weight into the optical tubes as close to the eyepiece as possible to give the desired weight distribution pretty much mandated SP prisms.

Lee

Kimmo, post 5,
You hit the nail right on the head with regard to SP-prism versus AK prisms. Perhaps an addition: AK prisms take more space , so binoculars will be slightly longer than binoculars with SP prisms.
Gijs

james holdsworth said:

I think you mean 32 mm FL's.....

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Of course, sorry, I mixed it up with Swaro's SLC line ...

Cheers,
Holger

The SF could be called light weight, but compact.......? hoho!

Gijs van Ginkel said:

Kimmo, post 5,
You hit the nail right on the head with regard to SP-prism versus AK prisms. Perhaps an addition: AK prisms take more space , so binoculars will be slightly longer than binoculars with SP prisms.
Gijs

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Not when you compare the Zeiss HT with the SF. 167mm vs 173mm.
Last night I saw Chris Packham on BBC TV using SFs and they looked very long, hanging from his neck.