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Fresnel spotting scope - next generation scope? (1 Viewer)

Vespobuteo

Well-known member
Nikons new super-light and compact Phase Fresnel 300mm f/4 lens makes me wonder if it would be a good idea to make a spotting scope with the same technology?

Nikons PF-lens is 50% lighter and 30% shorter than the original lens.

So it would probably be possible to produce a 85mm scope + eye piece weighing less than 1000 grams and also being very compact.

CA suppression is said to be very good in the nikon PF-lens, important also in a spotting scope.

Until now it's only canon and nikon that have made these kind of optic commercially?? so I guess a new Nikon scope is the most likely.
But I guess anyone (who knows optics) could do this.

What do you think? Possible? What would the image quality be?
 
I don't think this kind of lens will work well for visual optics. The problem is the "step" or "tooth" shapes of the Fresnel lens surface. They have some surfaces that run parallel to the optical axis. Those will reflect unwanted light from off-axis angles and pass it along in a way that is not image forming. The result is flare from unfocused light mixed into the image. You can see in the Nikon information below that the PF lens only works well in a Nikon camera with "PF Flare Control" included in the "Capture NX-D" software. That apparently processes the image to reduce the flare to an acceptable level in the photos outputted from the camera. Our brains don't have "PF Flare Control".

http://imaging.nikon.com/lineup/lens/glossary.htm#pf
 
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I don't think this kind of lens will work well for visual optics. The problem is the "step" or "tooth" shapes of the Fresnel lens surface. They have some surfaces that run parallel to the optical axis. Those will reflect unwanted light from off-axis angles and pass it along in a way that is not image forming. The result is flare from unfocused light mixed into the image. You can see in the Nikon information below that the PF lens only works well in a Nikon camera with "PF Flare Control" included in the "Capture NX-D" software. That apparently processes the image to reduce the flare to an acceptable level in the photos outputted from the camera. Our brains don't have "PF Flare Control".

http://imaging.nikon.com/lineup/lens/glossary.htm#pf

nikon says:

"when there is a strong light source within the frame or when light enters the lens from outside of the frame, ring-shaped colored flare may occur according to shooting conditions."

to me that seems like a non-typical scenario for most birding situations,
and a lens hood will help,
but maybe that could be a real problem, in some situations,

I think there could be a market for a very light and bright scope,
one example is low light observation,
hunters etc, that need a large exit pupil and don't want to carry weight.
 
Since PF scopes are nonexistent in the material world, and since Henry described its probable shortcomings for visual use, I find it proper to remind you that there already is a variety of scopes with similar properties, and to a certain degree also similar shortcomings, namely mirror scopes like Maksutov-Cassegrains.
Even draw tubes like the ones made by Swarovski, Meopta and Optolyth can serve the need for fullsize performance in a compact package.

//L
 
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Since PF scopes are nonexistent in the material world, and since Henry described its probable shortcomings for visual use, I find it proper to reming you that there already is a variety of scopes with similar properties, and to a certain degree also similar shortcomings, namely mirror scopes like Maksutov-Cassegrains.
Even draw tubes like the ones made by Swarovski, Meopta and Optolyth can serve the need for fullsize performance in a compact package.

//L

I think the problem with the fresnel-type lenses is that they have not been good enough, Canon made a 400/4 mk1 that was not very good but very expensive, the only selling point was the low weight, but the MKII version is MUCH better (released last year), so the technology is getting better.

the swaro CTS 85mm body is 1400 gram so its not very lightweight.


mirror scopes, hm, i dont know, donut-bokeh, low transmission??
 
the swaro CTS 85mm body is 1400 gram so its not very lightweight.


mirror scopes, hm, i dont know, donut-bokeh, low transmission??

Drawscopes:
The main concerns with drawscopes are the straight-through view, the lack of waterproofing which means they will need an interior cleaning sooner than the sealed and nitrogen-purged counterparts and the lack of ED glass in all of them.

Mirror scopes:
The donut bokeh is less objectionable for viewing purpose than for photography. Transmission can definitely be very decent, but the central obstruction makes them less bright than a refractor of the same front lens diameter. However, the decreased image contrast as compared to a top-class refractor is a deal breaker.
I have the not-so-high-end Celestron C90 and complemented it with a dielectric star diagonal along with some nice eyepieces. But it's always the Nikon ED82A I take out and I guess you could imagine why.
The superior image quality, that is also very good for photography (digiscoping).

//L
 
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