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Old Thursday 7th September 2017, 08:46   #1
Dynszis
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Kowa TSN-883 performance

Hi,

some time ago, I tried a Kowa 883 with a TE-11WZ eyepiece, and a Sony Nex 7 attached via PA7 adapter.

The results did not impress me, reasoning that even an imperfect focus or camera shake could not have caused these chromatic aberrations.

Still I am not sure what one can reasonably expect, and what I may have been doing wrong.

What do you think, when looking at the 100% crop I attached: User error, wrong setup, or did I try out a lemon?
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Old Thursday 7th September 2017, 21:55   #2
Apochromat
ZEISS VICTORY SF 8x42 KOWA 883 Prominar 25x-60x Wide

 
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Image aberrations without camera objective

Hello,
to my knowledge a system camera works aberration- free adapted to the KOWA TSN 880 using the 25x-60x Wide Angle PROMINAR eyepiece and a camera adapter (e.g. PA7 or DA10) only in conjunction with a camera objective, preferably one that for a MFT camera sensor has 20 mm focal length. I use the PANASONIC GX8 together with the 20 mm PANASONIC Pancake objective and I get stunning images absolutely free of CA or astigmatism.
Such strong CA you would visually also have to detect, e.g. looking at the edge of a white flower leaf. Than you would have a lemon. I have never seen something with KOWA and its PROMINAR products.

Without the camera objective you have to use the TSN-PZ adapter for aberration- free images.

See also here:
http://www.photoinfos.com/Spektiv/ko...ting-scope.htm

Tha
Michael
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Last edited by Apochromat : Thursday 7th September 2017 at 22:06.
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Old Thursday 7th September 2017, 22:47   #3
Dynszis
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Quote:
Originally Posted by Apochromat View Post
Hello,
to my knowledge a system camera works aberration- free adapted to the KOWA TSN 880 using the 25x-60x Wide Angle PROMINAR eyepiece and a camera adapter (e.g. PA7 or DA10) only in conjunction with a camera objective,
Hello Michael,

thank you. I guess this explains at least the CA part of that experiment.

Seeing that the 20mm Panasonic Pancake scores quite favorably on dxomark, it's probably a good option.
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Old Friday 8th September 2017, 18:18   #4
henry link
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What I see in the photos is latitudinal CA, not longitudinal. Longitudinal is what's famously low in the Fluorite objective of the TSN 880 and probably not much subject to sample variation. Lateral color could be from poor collimation of the scope optics or the camera lens or misalignment between the optical axes of the scope and the camera.

Last edited by henry link : Friday 8th September 2017 at 19:27.
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Old Friday 8th September 2017, 19:45   #5
Dynszis
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Quote:
Originally Posted by henry link View Post
Lateral color could be from poor collimation of the scope optics or the camera lens or misalignment between the optical axes of the scope and the camera.
Thank you, Henry. The above picture is a composite from four areas of the same photo. In each area the colors are shifted in different directions. Or rather, Blue seems to be shifted towards the center of the image, causing color fringes as a result.

Is this what you'd expect from poor collimation or misalignment between the optical axes of the scope and the camera?

Last edited by Dynszis : Friday 8th September 2017 at 19:52.
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Old Sunday 10th September 2017, 01:29   #6
Apochromat
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Lateral CA (Farbquerfehler, Vergrößerungsdifferenz der chromatischen Aberration)

The lateral CA would result in coloured images of different sizes but equal sharpness.

Your artefact is a mixture of coma (=astigmatism and spherical aberration) and its chromatic deviation. This most likely comes not from the scope optics as such but typically from a wrong optical adaptation of your camera, as the optical sine condition of the whole system for the different colours is not fulfilled by your adaptation. This can change with the sensor distance against the eyepiece. Because of that the above mentioned adaptation with a projective (as such the camera objective will act) will eliminate all this.

The lackmus test is to look at the visual image and its lack of such aberrations.

Thanks
Michael

Last edited by Apochromat : Sunday 10th September 2017 at 01:37.
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Old Tuesday 12th September 2017, 01:25   #7
b3rd
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I just took my TSN-883 out for a test run and while I was not running such a controlled test, I saw no hint of any flaw in the image. WOW. I was very impressed at what i could see.
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Old Tuesday 12th September 2017, 01:33   #8
Pileatus
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Quote:
Originally Posted by b3rd View Post
I just took my TSN-883 out for a test run and while I was not running such a controlled test, I saw no hint of any flaw in the image. WOW. I was very impressed at what i could see.
Whenever I look through my 883 I think, "If I ever find a bin that delivers this view I'll pay whatever they ask."
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Old Tuesday 12th September 2017, 06:48   #9
Apochromat
ZEISS VICTORY SF 8x42 KOWA 883 Prominar 25x-60x Wide

 
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Smile Superior KOWA TSN- 880

Quote:
Originally Posted by Pileatus View Post
Whenever I look through my 883 I think, "If I ever find a bin that delivers this view I'll pay whatever they ask."
Same with me.

If I look through other high- end spotting scopes (SWAROVSKI ATX 85 or ZEISS Diascope 85 T FL) I am always reminded of how superior my KOWA 883 with the PROMINAR 25x - 60x W eyepiece is.

Just wish the KOWA TSN- 880 would be SWAROVSKI rubber armored and would come with ZEISS anti-reflex coatings (KOWA is very good here too, but I like ZEISS most here, especially if the light is too bright out there). A prettier nylon case (without that funny looking leather KOWA logo) but with the same functionality would be great too.

I am glad, that the KOWA does not come with a water/dust- repellent front lens coating (e.g. LEICA Aquadura, SWAROVSKI SwaroClean, ZEISS LotuTec) as I very much dislike that for proper cleaning. It is good for users that cannot professionally clean a lens properly (water, ophthalmological cotton, wooden stick, GIOTTOS 1900 dust blower).

And yes keep that KOWA focussing system as it is.

The only thing I noticed is, that the KOWA 883 is a bit more sensitive against air turbulences at 60x compared to the ZEISS Diascope at 60x and 65x (maybe this is due to the slightly higher objective opening, 88 versus 85 mm).

I will have a look at the new HARPIA next year, BUT I would never want to be an early adopter of any LEICA, SWAROVSKI or ZEISS product.

I am waiting for a KOWA TSN PROMINAR 1000 or 950 with an eyepiece with CaF2-lens.

Thanks
Michael

Last edited by Apochromat : Tuesday 12th September 2017 at 19:51.
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