Camera Mirror Lenses Part 1: Visual and Interferometric Testing

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:
github.com/githubdoe/DFTFring...
Dale Eason DFTfringe group: groups.io/g/Interferometry/to...
Other videos on DFTfringe software:
• DFTFringe quick start ...
• version6
/ @daleeason9687
• Making a Mirror with a...
User experiences with the Vivitar 800mm mirror telephoto lens:
www.bhphotovideo.com/c/produc...
www.amazon.com/Vivitar-800mm-...
Syntax-Brillian Bankrupcy and Sakar aquirement:
seekingalpha.com/article/6660...
www.cnet.com/tech/tech-indust...
www.optyczne.pl/1093-nowo%C5%...
www.sakar.com/
Original Vivitar 800mm Solid Catadioptric:
www.photo.net/forums/topic/50...
www.dpreview.com/news/3295932...
Vivitar rebranding:
mikeeckman.com/2016/12/vivita...
Star field Foto (by Felix Mittermeier)
www.pexels.com/photo/galaxy-s...
Bokeh bird in garden photo (by kenetik):
forum.mflenses.com/vivitar-ser...
Tommy Cooper photo: panorama.nl/artikel/174764/ko...
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.

[@chopper3lw]

Your explanations are wonderful. I had a realtime holographic interferometry project in the 80's and as a software engineer I was very much out of my field, but I've always enjoyed optics since. Your channel covers interesting aspects without getting too deep in the weeds. Thanks

[@pcaridad]

Agree

[@jannejohansson3383]

Yep, enough deep to get new info and understanding, but not brain surgery..

[@GuagoFruit]

Optics is one of the most taken for granted technologies in humanity. Love seeing it explained in detail.

[@colinbrown7947]

Just wanna say this channel inspired me to major in optical engineering at my college! We are one of the few universities in the US with a dedicated optics program, and I'm blessed to have it in-state

[@GoldSrc_]

This is the type of content that youtube should be promoting more.

[@HuygensOptics]

Gordon! It is probably Half a Life time ago since we last met!

[@SalahAl-DinYusufibnAyyub]

‎

[@nweston5070]

Masterful understatement of the difficulty of doing those interferometric tests!

[@HuygensOptics]

Yes that is why I put a warning in the video: it looks simple but in practice it is really quite difficult to do correctly.

[@AdmiralSym]

I have three mirror lenses and I turned my Tamron 500mm f/8 into a tabletop telescope by removing the infinity focus stop and attaching a prism diagonal. Works great and is extremely portable

[@AdmiralSym]

I could talk about mirror lenses all day!

[@randallstewart175]

Tamron sold a very high quality right angle prism/eyepiece with magnifier to attach to the mirror lens in lieu of a camera. There is also a doubler to increase the telephoto focal length at a modest cost of reduced performance (which should not matter if using the lens as a telescope). These accessories connect with the Tamron proprietary Adaptall II interface, so are not usable with non-Adaptall mount lenses. I've intended to use this combo to watch an eclippse, but so far I forget to set up fot it.

[@mal2ksc]

@@randallstewart175 Just remember you lose two stops when you insert a doubler. In terms of light-gathering capability, you have an f/16 lens.

[@AdmiralSym]

@@randallstewart175 I’ve seen the “02F” come up in my research but they’re pretty hard to find! I see one on eBay with with a starting bid of $50! I wonder if i can make something like this myself using surplus binoculars prism optics

[@randallstewart175]

@@AdmiralSym Tamron made an Adaptall II doubler, 6 element, fairly high quality, which fits all of those lenses, the 01F. This is quite common and cheap, commonly in the range of $20 - 40. They also made a model 200F, also a 6 element doubler with ED type glass, which is very high quality and gives a much better optical performance than the 01F. It is very rare and fairly expensive as doublers go. It does not fit most Adaptall lenses except for prime and zoom telephotos. If a 500mm mirror lens is used as a telescope, either doubler will fit, but the optical advantage of the 200F will mean little or nothing because it's improvements show in the edges and corners of a photo image format, probably outside the visual area of a telescope usage, and the human eye' would probably not see the difference anyway.

[@skelingtonrick]

I really appreciate your casual total mastery of the subject of optics. it makes your explanations very clear and easy to follow

[@nuffsaid0]

One of the absolutely excellent channels on youtube. Pure gem.

[@thethirdman225]

This is terrific. You get so many self-appointed lens experts that it's really refreshing when someone actually demonstrates and explains what's really going on. As someone who has had to test lenses as part of my job (I spent three decades in film, television and photographic industries), I'm aware of how misleading some of the comments online can be. I'm really looking forward to seeing how these turn out.

[@Nickle314]

This illustrates why YT and other services are so cool. Where would you even find out in the past about things like this, and see it for real. Very good.

[@OccultDemonCassette]

Oh man, improving vintage photographic lenses is 1000% in my interests. This is the kind of content that I've been dreaming about! Can't wait for part 2!

[@klx6265]

Really grateful to you for providing me with knowledge free from any ideas of profit. There's a certain purity to enjoying knowledge handed down this way, that evokes a child like wonder in the mind. I am in no way connected to the field of optics, but I love watching your videos for the sheer education they provide. Thank you sir! God bless! :)

[@hrtlsbstrd]

A tremendous transfer of knowledge for interested amateurs as usual. Thanks so much for putting your expertise out here for us to enjoy!

[@AppliedCryogenics]

Another magnificent episode! Apparently, I'm strangely excited about non-monolithic reflecting lenses also. Thanks for broadening my horizons. Looking forward to next ep.

[@peterschrauth90]

Thank you for bringing back memories of my FIRST 35mm film camera, a Vivitar SLR with 1.8f ~50mm lens, circa 1968. 😊

[@rolandrick]

Wow 🤩! Can’t wait for part two. I once studied mechanical engineering, because it’s interdisciplinary covering kinda all fields of natural sciences, qualifies you to put the things together, understanding the big picture as good as possible. Watching this channel, I realise we were back then deprived of the most interesting one, optics. My brain literally sucks in each world like a sponge. To me, this is the most interesting channel on KZbin.

[@CanyonWanderer]

What a great explanation! Those optical setups remind me of my graduation project which involved optical rails, an IR laser diode an .95 Aperture lens (still fascinated by how that was possible), a 3D object and a special sensor (the actual subject of my project). The other part of the project was making software to read out the sensor. After 6 years of studying Applied Physics and graduating, I turned to become a software developer for the rest of my life 🙂Still fascinated by anything related to physics / optics of course. By coincidence, 20 years ago, I got married 700 meters from my house in Hofwijck, former residence of the Huygens' brothers 🙂

[@glentyan2505]

Excellent Video as usual. Speaking as an Astrophotographer I can say without question of doubt that imaging a field of stars places the most difficult test of any optics as stars contain wavelengths from UV to IR and as the stars are round recreating this faithfully on Film, CCD or a CMOS colour device is extremely difficult and very expensive. This is due to the need to focus all wavelengths to the same spot equally regardless of wavelength to retain roundness and point spread function (PSF) across the field. Every single type of aberration you can think of may show up in even the most expensive of optics. For mirror optics the percentage of obstruction should be low for planets to retain the detail and as the field of view increases so does the obstruction ratio but nebulae and star field images are not affected by this. However using a big chipped camera with a low obstruction ratio will result in unacceptable light fall off from the centre of the optical axis. So, if you want a quick way to test optics ...... try pointing them at the stars as many of these errors are not readily noticed on terrestrial images.

[@iestynne]

Is using a filter to narrow the light spectrum a viable approach?

[@glentyan2505]

@@iestynne For what purpose?

[@iestynne]

So you only need to deal with monochromatic light

[@glentyan2505]

​@@iestynne I take we are talking about Astrophotography and the answer is yes however that answer could be an hours long video in itself. When dealing with monochromatic light we get smaller tighter stars due to the better control of LCA (longitudinal Chromatic Aberration) assuming of course focus is perfect. The main filters we use are Red, Green, Blue, H-Alpha which is at 656nm a deep Red and is Ionized Hydrogen, O111 (Oxygen 111) , and S11 (Sulfur-11). We also use a Luminance filter which is clear. The Ha, O111 & S11 are classed as Narrowband filters and these colours when mapped give a different palette the most popular being the Hubble Palette which blue and Yellow resulting images. As I said the topic is vast, just hope I've answered the right question. 🙂

[@blablabliam]

Excellent description of Strehl. Too many people think that that is the only number that matters in a telescope, and will flip out over very minor differences from one to the next. As you say, in optical design there must be compromise, and Strehl is only one of many parameters deciding the usefulness of the optics. Love these videos!

[@JoseSilveira-newhandleforYT]

Surprisingly accessible video, having in mind the complex concepts involved. Very interesting to watch. Looking forward to Part 2 🙂

[@user-cr5wt6gl2o]

Oh, and here you've triggered me to dive in optics once again... What a wicked trick!

[@nabintimalsina5628]

I like watching your videos on Optics. You describe things very well.

[@mishun]

I will never ever be able to emphasise enough how cool is this channel

[@isoslow]

This is content out of pure gold. Very good and interesting. And I can't wait to see part 2.

[@Pesc0-conti]

This channel is literally a goldmine of knowledge. Thank you so much for all the effort you put into making these videos. You're awesome

[@makerbeelab5546]

Ah I'm already looking forward to the Mr Squinty's magic transformation!

[@MarkxTube]

This takes me back when i put all my money together as a teen to buy a MT1000 russian masukov mirror lens and then being soo disappointed on the image quality. I wish i could have made it better. Looking forward to the next video.

[@mceajc]

Every video you produce astonishes me with your knowledge, passion, humour and clarity. Always appreciated!

[@smellslikeupdog80]

there is so much information in each video's brief overview I deeply enjoy a dive into a feild I wouldn't otherwise be exposed to

[@arjovenzia]

Vey interesting, keen for part 2. I picked up a No-Name 500mm mirror lens from eBay, ridiculously cheap ($120AUD), purely out of curiosity. Its very fiddly to use, the focus ring feels gritty, and there is very little margin between being over or under exposed, so I never use it for anything serious. But it is Fun to play with, and for me, that's the most important thing about a hobby. And I have taken some really cool photos with it. I cant justify spending thousands on a interesting lens, but a hundred bucks? sure! I guess I wanted to point out that a super cheap mirror lens, whilst does feel cheap, can be good enough for a bit of fun, and worth getting if you'd like to play with something a little different.

[@parranoic]

Stuff I wish I learned in my physics class. You managed to keep my attention through the full 21 minutes, great job

[@TheHouseBlog]

I really appreciate the effort you put into your video content overall, it's top notch. The pacing of your videos and the quality and readability of your graphics really stand out.

[@AlejandroMironov]

Absolutely fascinating! Your delivery of information and knowledge is absolutely on point. Can’t wait for the next part!

[@yiyou6529]

I have been talking to my colleagues every day about how eager I am to see the Part II of this work.😁

[@OrionFyre]

Jeroen, I just want to say I always get giddy whenever I see a new video from you. Your explanation of the physics and science in application is always impressive. I appreciate all the time and effort you put into your productions and the sharing of your expertise and experience.

[@michaelseitz8938]

Damn, this video is such a teaser! I can't wait to see the results of your repairs 😁

[@kimrosland]

Add still playing but I know this will be interesting!

[@MJano79]

The moment has come when I look forward to the second part of a KZbin video more than the next episode of Game of Thrones. 😊 Everyone wants to work with a professional like you! Thank you!

[@GregCoonrod]

I don't know anything about optics but your explanations are very accessible and entertaining! I look forward to seeing how much you're able to improve those lenses.

[@ARVash]

Every single video you make is hugely eye opening! Thank you so much for all your contributions to global freely available knowledge.

[@bansci]

Amazing video, thoroughly enjoyed the technical detail, humour, concise focus on the topic, and thread of the story! Something to aspire to

[@kudui21]

This has been a treat. Can't wait to see future episodes of this series.

[@kevinocta9716]

Oh this is awesome! I had looked for a video like this for years about how exactly people test telescope mirrors and what the different numbers mean etc with little success. I found some very scholarly articles that went far above my head with almost no visual representation so they were extra hard to understand without a background in optics. Thanks! Side story: I had to clean my telescope mirror for the first time. Overall it was really easy, but when I put everything back together I could not get it collimated for the life of me. Turns out it was that mechanical stress you talked about, only my diffraction patterns (or in my case just defocused patters) didn't show up like most people showed, which made it take forever to figure out. The real reason was that only one of my mirror holder clamps was really putting any stress on the mirror, so the astigmatism was very asymmetrical not matching the 120 degree astigmatism you showed here. If I had seen this video first, I bet I would have saved hours!

[@davidwillmore]

Your pronunciation was perfect, sir. Nothing to apologize for!

[@Petars24]

Amazing work, I appreciate your depth and breath of knowledge on this subject. I look forward to the next video, regarding the possible upgrade of the mirror lens.

[@xavierdemers-bouchard2747]

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.

[@AdamvanAlderwerelt]

I have no idea how I got here, but this video was really cool. This was so educational and I really appreciate the work you put into these videos.

[@jim5148]

I've always been fascinated with optics, and I thoroughly enjoy your videos. I can hardly wait for the next one. Thanks!

[@d37tae]

Super excited about this series! I love the idea of measuring and fixing off-the-shelf and old optics.

[@LaViejaConsolada]

If only I could have someone like you at my disposal to teach me stuff... Fantastic video!

[@markfallu2389]

I really appreciate the "clarity" of your explanations (no pun intended)

[@LiyangHU]

6:21 Your pronunciation of boke / 暈け is spot-on; your Dutch accent actually helps. :) It's of Japanese origin and just means _blur, haze, fade, … & c._

[@bjnslc]

In its "before the web use", the word specifically meant aesthetic quality of that blur. Donuts are tasty, but make for very bad bokeh.

[@aclearlight]

A very efficient, lovely intro class in practical optics, thank you SO much! Looking forward now to part 2!

[@PixelSchnitzel]

I absolutely love this channel. Optics are well outside my abilities, but your explanations make a lot of sense and inspire me to continue learning and to experiment on my own. Thanks!!!

[@marianl8718]

Hi ! I am from Romania and I watched your video with pleasure and with nostalgia, because I also spent a long time grinding and polishing telescope mirrors of all kinds, spherical and aspherical, including hyperboloidal. I was cheching using the Foucault method, sometimes in combination with autocolimation, I didn't have the possibility to use interferometric methods. I even built a telescope with a bronze mirror, like in Newton's time ! BTW, very good photografic images can be obtained with a simple Newton telescope, but it is too large. I was amazed that the manufacturers did not care that the mirror surface could be deformed by tightening some screws ! That's all I thought all the time !

[@jmannUSMC]

This channel always scratches that itch for knowledge. I know nothing of optics really but oh boy do I love learning new stuff about it.

[@davidjoelsen3399]

It is a true pleasure to listen to all the information you present - never knew that optics were one of my favorite subjects.

[@MisakaMikotoDesu]

Thank you for tying physics into photography. Both are super interesting, and having them combined is good stuff. Your video are great!

[@jeromejooste3493]

Great explanation and video. Can't wait to see how you tackle the refiguring of the optics.

[@goranjosic]

Can't wait for the next video! Surprisingly interesting! As usual on this channel!

[@lumotroph]

Brilliant to watch as always. Thank you 😊 looking forward to the next part!

[@GTheoMedia]

Amazing preciouses information showed very well. I have the 800mm and it's decent during the day in the sunlight but always had a hard time focusing on the stars at night.

[@mrcpu9999]

I get that this is a super complicated field. But your explanations continually help me understand this way better than I ever thought I would. Good stuff.

[@allenmaudiln]

This was such a fascinating video! I’m really looking forward to the next one.

[@theheavensdeclareastro]

I love watching your videos! So fascinating and so well-explained, thank you!

[@antoncronet6104]

I know very little in the field of optics, but i really enjoy the content and find it is always perfectly explained

[@danielnorman8595]

Wow just found this channel you have a new subscriber. Very fascinating. A journey into understanding optical designs is one I would enjoy taking

[@kilianschoenenberger1995]

I found my new fav channel! Just so happy i found your videos!!

[@Jimmymcjimthejim]

Excellent detail and presentation. Thank you!

[@qwerty123443wifi]

this is exactly the kind of niche but extremely interested stuff that I'm in to! Love this channel, thanks for your work :)

[@jgurtz]

Wonderful video! Really enjoyed the introduction to interferometry and look forward to the next part.

[@4n2earth22]

Excellent presentation; highly informative. Looking forward to the next vid!

[@ParedCheese]

Looking forward to seeing how you collimate the Soligor.

[@lartsevevgenii6640]

Absolutely amazing source of pure knowledge! Thank you so much!

[@sebaschtl9710]

Thanks for sharing you knowlege. I enjoy your professional explaining so much.

[@gyrogearloose1345]

Very interesting . . . thank you for sharing your knowledge. Looking forward to Part 2 and more. Great to see Tommy Cooper at 4:57 !

[@4dirt2racer0]

idk anything about optics n im especially no photographer, but u still make these videos interesting somehow, im genuinely excited for part 2 to come out u do awesome videos man thanks, its nice having worthwhile stuff to watch

[@HuygensOptics]

Part 2 is already out, but somehow not really promoted by KZbin: kzbin.info/www/bejne/Z3LdgmevlNaqqK8

[@4dirt2racer0]

@@HuygensOptics hmm that's strange..I even specifically searched for it on ur channels page.. would it help if I mentioned something to KZbin about not being able to find it? Btw thanks for the reply n bringin part 2 to my attention

[@AnaloguePhoto]

Great video! It went by like it was only 3 minutes long. Afterwards I had a look at the date it was posted, hoping it would be a few months since... I had hoped to see the follow-up video right away. Suppose I'll just have to wait. And I'm really looking forward to that coming video. Thanks Jeroen!

[@realcygnus]

Superb as always ! Optics is arguably one of our most useful discoveries. We probably wouldn't even know about bacteria or galaxies for instance otherwise.

[@user-oj4xh8cg2l]

clear, focused and to the point : thank you for this pretty sharp video !

[@WhiteVaille]

This looks so fun to tinker with. Thank you for sharing your "toys" and this journey with us!!

[@Veptis]

Thank you for bringing this highly technical content and explaining it really well.

[@Sigmatechnica]

Facinating! Looking forward to the next installment!

[@abacabdk3490]

Great videos, you explain very well and there is a good balance of practice and theory. Looking forward to the next one. Thanks.

[@photography_night_school]

My favorite channel) Thank you for your knowledge!

[@markatherton7848]

Excellent video as usual; please keep up this great work.

[@simonstergaard]

Thankyou for always de-mystifying optics. Cant wait for part 2 !!!!

[@sean_vikoren]

An absolute delight hanging out in your lab, as always.

[@anga6275]

this is a great channel. i don't know anything about optics but this encourages me to learn. cheers!

[@crownlands7246]

Another razorsharp delight 🙏😊☀️🌱

[@Capitaine.Albator]

I know nothing in lenses or optic. But your way of explaining is so much clearer. Thanks for content 👍🏻✌🏻🇨🇦

[@manufranc0]

wow ! I was not expecting such a video! thank you for this ! subscribed!

[@luke2642]

Another great video, looking forward to seeing the repairs!

[@TheMeccio]

This is literally a pure diamond of content inside youtube. Very well done!

[@jonc133]

Really nice piece of work. Thanks for sharing.

[@afryhover]

Very interesting. Thanks for making this. I own and enjoy shooting with my Nikon 500mm F8 reflex lens.

[@xs6819]

Hi Jeroen Thanks for posting these videos they are awesome.

[@blooregart]

This is my favorite youtube channel right now

[@joshuam511]

Excellent video. Really looking forward to part 2 :D

[@derekokeeffe9919]

Great video. Look forward to the next one