In this video I will discuss the visual and interferometric tests of camera mirror telephoto lenses. Contents:
0:00 intro
1:16 Vivitar f=800mm F:8 mirror lens
4:58 Sigma f=600mm F:8 mirror telephoto
7:34 Soligor f=500mm F:8 mirror lens
8:26 Explaining interferometry in auto-collimation
12:09 Actual interferometry measurement setup
14:58 About Strehl Ratio
17:15 Strehl ratio and aberrations of Vivitar 800mm mirror lens
18:18 Comparison with results of Sigma 600mm mirror lens
20:17 Extro
EXTERNAL SOURCE LINKS:
DFTfringe software download:
https://github.com/githubdoe/DFTFringe/releases
Dale Eason DFTfringe group: https://groups.io/g/Interferometry/topic/test_with_dftfringe/28806172
Other videos on DFTfringe software:
https://www.youtube.com/channel/UCPj57WFSSLpVqPir7Im-kiw/videos
User experiences with the Vivitar 800mm mirror telephoto lens:
https://www.bhphotovideo.com/c/product/885034-REG/Vivitar_v_800mr_800mm_Mirror_Lens_for.html/reviews
Syntax-Brillian Bankrupcy and Sakar aquirement:
https://seekingalpha.com/article/66607-will-syntax-brillian-survive
https://www.cnet.com/tech/tech-industry/sakar-acquires-vivitar-brand-and-ip/
https://www.optyczne.pl/1093-nowo%C5%9B%C4%87-Vivitar_na_sprzeda%C5%BC.html
https://www.sakar.com/
Original Vivitar 800mm Solid Catadioptric:
https://www.photo.net/forums/topic/509542-vivitar-series-1-600mm-f8-solid-catadioptric-telephoto-lens/
https://www.dpreview.com/news/3295932675/canon-patents-400mm-f5-6-catadioptric-mirror-lens
Vivitar rebranding:
Star field Foto (by Felix Mittermeier)
https://www.pexels.com/photo/galaxy-space-957010/
Bokeh bird in garden photo (by kenetik):
http://forum.mflenses.com/vivitar-series-1-600mm-f8-solid-cat-and-a-bird-in-the-garden-t69033.html
Tommy Cooper photo: https://panorama.nl/artikel/174764/komiek-tommy-cooper-stierf-35-jaar-geleden-in-het-harnas
End music: “Floating” performed by the Early Birds (recorded in Eindhoven in 2000).
Did I forget to mention you above and are you a copyright owner? let me know and I will set it straight by linking to your original content in these credits.
34 Comments
Is he going to fix it? Is the concept poop or just the quality?
I have the 600mm Vivitar catadioptric lens and it's asserting the same problem as the 800mm that you did show.
Man, those chimneys look f'ed up 😂😂
Thank you for tying physics into photography. Both are super interesting, and having them combined is good stuff. Your video are great!
Can't wait for the next video! This is so interesting but I think this has something to do with your approach. I would listen to you for hours. Such a great balance in taking us along and explaining what's going on in a way that doesn't make me feel like I'm being talked down to. My hat to you sir.
I had one of the Sigma 600mm lenses in Olympus mount back in the 80's. I never really found a good use for it. I recall a filter drawer in front of the lens mount. It could be fitted with a small filter. There was a set that came the lens including a red and yellow filter for black and white and one or two neutral density filters.
..at 730..showing the moon zoomed in… somehidng flew across the face? …i wonder
THAT WAS AMAZING !!!! GREAT VIDEO
This was a great video.
The Singer company sold 300mm and 600mm (!!!) f1.8 catadioptric lenses for 40mm format film. Imagine the eldritch bokeh
Pitty you did not test the worlds only mirror lens with auto focus: the Sony/Minolta 500mm F8
The PewdiePie lense is the best
You must try the best mirror lens ever. Minolta AF Reflex 500 f / 8
I have one and with Sony A7m4 it works great with the LA-EA5 adapter.
Very interesting. Thanks for making this. I own and enjoy shooting with my Nikon 500mm F8 reflex lens.
Very good.
I'm not a photographer or anything. My biggest achievement in the field of optics is the fact that I have to wear glasses. But man, these videos are so interesting.
I am curious, in your interferometer set-up, would it be better to replace the spherical mirror with a parabolic one to produce 'higher quality' spherical wavefronts?
Seeing your videos I become more and more keen on optics. Do you have any book to advice for studying this matter?
I don't know if it would be interesting and challenging enough for you, but might you consider making a low cost hyperspectral camera? I made my first attempt over the Summer and to my surprise it actually worked, although very poorly. Going by memory here, I think I had around 500 colors which was good, but it was very blurry. I'm a little proud I made it with stuff I had laying around–computer camera, transmission diffraction grating or DVD for reflection, razor blades, magnets and duct tape. It used pushbroom style imaging which was done by me moving it slow with my hand. In other words, you would die laughing at it. I would be interested in seeing how you think the project through and how you would build it.
In my opinion this construction is similar to maksutov cassegrain telescope
I haven't a clue how this video was directed at me, but somehow the algorithm got it right. Found this absolutely fascinating.
Ik verbaas me toch steeds weer over uw kennis and ik deze videos bekijk!
A friend mentioned in his previous job he was operating machine that 'polish' silicon wafer for semi-conductor industry. After some googling, it appears that the "Plasma Etching is the removal of plastic, silicon, or other non-metallic material using plasma created by exciting ions in a gas, usually oxygen and CF4. "
which makes it an ideal tool for polishing a lens.
I think, it should be a dry and non contact process, so the etching and fringe lines inspection could be done continuously.
YOU ARE MAD! <3
Dang I bet that lense is perfect for accidentally capturing low quality UFO footage.
Pure excellence.
Out of curiosity: What would the Strehl ratio be of 'high-quality' lenses in photography, like a 50mm 1.4 'standard' prime (perhaps stopped down to improve optical performance?)
I would be interested in a comparison between the Strehl ratio and MTF charts, which is another way people often 'rate' camera lens optical performance.
Finally, how is chromatic performance taken into account here? Would you repeat the measurement vs wavelength and plot a 'strehl vs wavelength' ratio? I believe for a lot of camera lenses this is an equally important metric (though I guess that it is a lot easier to get rid of chromatic abberations in numerical algorithms than it is to compensate for lens softness, though in the end both are a 2D transfer function so I imagine it should be possible to apply the reverse on the image field in numerical algorithms?)
So many questions!
Thanks for the videos!
WonderfulVideo! Looking forward to part 2
This looks so fun to tinker with. Thank you for sharing your "toys" and this journey with us!!
I felt this video kept me well interested the who time.
Absolutely love this video, Thank You !
I send quite a bit of time on CloudyNights ATM forum, so this is right up my alley 🙂
Chinese manufacturers are the second biggest Scammer scumbags in the world. First place was and still are call centers from India they get the scumbag award daily XD
Can't wait for the conclusion!
I had my primary mirror on my 150mm Newtonian refigured by an optical company to .986 Strehl ratio and .08 wave with a zero knife edge test at >.01mm. Takahashi quality for $500 on a used Celestron reflector. A Strehl ratio in a telescope less than .750 is unacceptable. Even before I had my mirror refigured it was better than .750 Strehl. I had both my mirrors recoated to 96% reflectivity. Guys at my astronomy club are envious. 😉
My Sky-Watcher 102mm Maksutov-Cassegrain telescope with 1300 focal length and F-12.7 ratio comes with threads for a standard dslr camera after I remove the eyepiece diagonal is just a giant catadioptric compared to those. My son put his Canon onto it and suddenly could take photos or videos of Saturn or even Uranus. I set my mount to track Bode's Galaxy and it only took three 5 minute exposures to get a very good picture of poster quality. I haven't been able to get my telescope back from him.