Page 2 of 6 FirstFirst 1234 ... LastLast
Results 11 to 20 of 60

Thread: Apo-Ronar shims--one, two, or none?

  1. #11

    Join Date
    Jul 2016
    Posts
    4,566

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Randy Moe View Post
    Another question is how do we make and use a DIY Optical Bench.
    Randy, this is straight... My bench is my Norma "optical bench" with also a lens board in the back standard, I've two special lens boards, one has an F mount bayonet on it to attach a dslr (without the dslr lens,projwecting on the sensor), the other one has an x20 eyepiece. This isn't a pro bench becuase it's not precise enough to account for the field curvature, but with shifts/rise it allows to reach the circle boundaries, if checking focus again for each time we move the position then we have good information, good enough to check the best shimming.

    The shim is calculated by counting the tours we unscreew until the optimal position, and then we multilpy by the thread pitch. It requires some work because we need to balance the effect in the center vs corner.

    A dslr may have 250 pix per mm, so some 125 "pixel pairs" per mm, this may be good enough for this optimization work, or even we may use other (cheaper) cameras with a very small sensor having a higher pixel density, like an old smartphone with its lens removed, this is a nice solution because we see the screen in the other side, and we operate the camera from that screen, or with a regular mouse attached to the usb with an OTG adapter. I had used the mouse to remove vibrations.

    I made tests with a Sony Z2 that has the lens broken, sensor is 1/2.3 diagonal having 5248 pix in 6.17mm, so 850pix/mm, so a trash Z2 with the lens broken, glued on a sinar lensboard and with a PC mouse OTG connected... this is actually a high precision instrument for DIY optics!

  2. #12

    Join Date
    Jul 2016
    Posts
    4,566

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Bernice Loui View Post
    Absurd (Those ??? LPM numbers again) to apply test from a single lens sample to the entire production of any lens. That individual lens test is a specific isolated test example
    Not absurd, Mr Perez and Mr Croell did something interesting in photography, this is testing, rather than eating commercial information and repeating urban legends.

    From the several croell/perez tests it looks that APO Ronar is not optimized for f/22, this looks it was a urban legend that had been repeated around.

  3. #13

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Mark Sampson View Post
    There ain't no free lunch!
    Ha, very true--though after the better part of century, trying to sift happenstance and accident from (intelligent ) Design can be a little nerve wracking!

  4. #14

    Join Date
    Sep 1998
    Location
    Loganville , GA
    Posts
    14,409

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Pere Casals View Post
    Not absurd, Mr Perez and Mr Croell did something interesting in photography, this is testing, rather than eating commercial information and repeating urban legends.

    ...but from the several croell/perez tests it looks that APO Ronar is not optimized for f/22, and that this looks it was a urban legend that had been repeated around.
    Nonsense! This test is unrepeatable and extremely variable. Just how fresh or fatigued one’s see is will skew the results!
    Not to mention atmospheric conditions, emulsion, processing, etc.. plus he apparently tested used lenses so previipus handling (has it been dropped), etc. enters into the results.

    It is simply stuff and nonsense!

  5. #15

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    8,470

    Re: Apo-Ronar shims--one, two, or none?

    Bob, on the one hand misinformation is worse than none.

    On the other, we all do informal acceptance tests, if only because no two lenses of the same make and model perform exactly alike. There's no substitute for asking the lens in hand whether it meets my needs (not necessarily your needs, and even if your needs are mine you don't have my lens).

  6. #16
    Tin Can's Avatar
    Join Date
    Dec 2011
    Posts
    22,387

    Re: Apo-Ronar shims--one, two, or none?

    As I have a Horseman Optical-Bench Modular Camera I will copy your lead.

    Thank you


    Quote Originally Posted by Pere Casals View Post
    Randy, this is straight... My bench is my Norma "optical bench" with also a lens board in the back standard, I've two special lens boards, one has an F mount bayonet on it to attach a dslr (without the dslr lens,projwecting on the sensor), the other one has an x20 eyepiece. This isn't a pro bench becuase it's not precise enough to account for the field curvature, but with shifts/rise it allows to reach the circle boundaries, if checking focus again for each time we move the position then we have good information, good enough to check the best shimming.

    The shim is calculated by counting the tours we unscreew until the optimal position, and then we multilpy by the thread pitch. It requires some work because we need to balance the effect in the center vs corner.

    A dslr may have 250 pix per mm, so some 125 "pixel pairs" per mm, this may be good enough for this optimization work, or even we may use other (cheaper) cameras with a very small sensor having a higher pixel density, like an old smartphone with its lens removed, this is a nice solution because we see the screen in the other side, and we operate the camera from that screen, or with a regular mouse attached to the usb with an OTG adapter. I had used the mouse to remove vibrations.

    I made tests with a Sony Z2 that has the lens broken, sensor is 1/2.3 diagonal having 5248 pix in 6.17mm, so 850pix/mm, so a trash Z2 with the lens broken, glued on a sinar lensboard and with a PC mouse OTG connected... this is actually a high precision instrument for DIY optics!
    Tin Can

  7. #17

    Join Date
    Jul 2016
    Posts
    4,566

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Bob Salomon View Post
    Nonsense! This test is unrepeatable and extremely variable. Just how fresh or fatigued one’s see is will skew the results!
    Not to mention atmospheric conditions, emulsion, processing, etc.. plus he apparently tested used lenses so previipus handling (has it been dropped), etc. enters into the results.
    It is simply stuff and nonsense!
    Bob, those tests (Perez-Croell) are of extreme value, if undertanding the limitations of a practical tests.

    Of course it is possible that some of the tested samples are flawed lenses or bad tests, and many fetures of lenses are not evaluated, but if Christopher Perez say that the APO Ronar he tested resolved 76lp/mm in the center at f/11 then I know for sure that he discerned lines of the 1.6 Element in a 1:20 magnification shot. I've no doubt.

    So perhaps that APO Ronar was better than 76 if he did not adjust focus well... but it's for sure that it is not worse.

    Beyond that Arne Croell tested 5 APO Ronar samples: http://www.arnecroell.com/lenstests.pdf

    In this case (Croell) Cycles are checked at 50% and 10% Modulation Transfer, so to me there is no doubt about how APO Ronars behave versus aperture in the 45 frame and under the reported test conditions. No doubt, Ronars are not better at f/22 than at f/16, as Ronars are very fine lenses.

    We have two independent tests of the 240mm showing better performance at larger apertures, additionally Croell tested a 300mm that was also better at f/16 and three 360mm that were poorer performers but mostly equal at f/16 than at f/22.


    In both (pérez-croell) tests (1:20, 6m) atmospheric conditions are irrelevant, in both cases they used TMX 4x5 sheets... both men are very skilled technicians. Well, having 6 Ronars tested, in this case, something can be concluded, isn't it?

  8. #18

    Join Date
    Jul 2008
    Posts
    3,901

    Re: Apo-Ronar shims--one, two, or none?

    The troll to be entertained....

    NO monorail view camera can equal a proper optical table to be set up for proper optics testing as it begins with a device like this:
    https://www.thorlabs.com/newgrouppag...tgroup_id=5930

    Then there are precision optical fix'ens required to do a test set up. This does not include the MTF testing instrumentation.

    As for "counting turns of threads" to determine shim thickness, you're dealing in fractions of 0.001" or 0.01mm which is easily the slop in any threaded system. This does not account for change in metal dimensions due to compression from tightening threaded parts or changes in parts due to changes in temperatures. Know the world of optical stuff works in wavelenght of light and very precise mechanical dimensions. Optical designs can be done to accomodate mechanical and optical tolerances, to achieve a real world-physical lens that can approach the calculated-therotical design all optical and mechanical aspects of the design must be accounted for, then tested with extreme precision and experienced expertise.

    -What are YOUR qualifications to do any of this?

    Outback shack methods and ideology can never equal precision designed and made for the needs of optical testing coupled with experienced optical expertise.

    Test using film is a combination of lens & image source & film & processing & visual judgement result.. NOT the actual performance of the specific lens under test.

    As for APO Ronar not being optimized for f22, Contact Rodenstock direct to discuss this with one of their technical support engineers.



    Bernice

  9. #19
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    18,338

    Re: Apo-Ronar shims--one, two, or none?

    Bernice - any statistical sample variation between lenses due to alleged quality control issues would be pretty low on my list of things that can be potentially misleading in a situation like this one. A lot of testing methodology is itself suspect. I always laugh when such an such a person's data base is considered trustworthy, yet they probably established it in the first place with either film sagging unevenly in a conventional holder or with fatigued eyes. Percival Lowell was convinced he saw canals on Mars. Well, that's what fatigued eyes do. And, as you just stated, equating monorail cameras to true scientific optical benches is sheer bunk, no matter how they might have been once marketed. But gotta run and do some scouting with my own Norma.

  10. #20

    Join Date
    Jul 2016
    Posts
    4,566

    Re: Apo-Ronar shims--one, two, or none?

    Quote Originally Posted by Bernice Loui View Post
    As for APO Ronar not being optimized for f22, Contact Rodenstock direct to discuss this with one of their technical support engineers.
    Arne Croell, he is a member IIRC, he tested 5 APO Ronar samples, at 50% and 10% MTF, in the center/mid/corner, for tangential and for sagital. This is enough for me.

    http://www.arnecroell.com/lenstests.pdf

    It has to be noted that even in the case that a lens is optimized for best performance possible at f/22 still the lens may still perform better at f/16 than at f/22. This has been a source of controversy...

    Perhaps this is the case...


    ________________


    Regarding camera alignment, it should be pointed that a 240mm at (1:20) 6m far and f/16 has 2m DOF for practical photography. A test requires more accuracy.


    Click image for larger version. 

Name:	dof.jpg 
Views:	14 
Size:	31.6 KB 
ID:	191110

    I guess that both Pérez and Croell could be able to focus/align well enough...


    I think it's quite easy to see when focus and alignment is influential in a test, at 6m f/16 it isn't at all, because in this situation the CoC provocated by aligment errors of a good LF camera are lower than the lens performance, also we correct very well the alignment with easy procedures, we can make the calculations if you want:

    Click image for larger version. 

Name:	dof2.JPG 
Views:	8 
Size:	29.0 KB 
ID:	191115

    By imposing a 0.007mm CoC we would have 130mm DOF. By focusing wide open, then aligning the camera to have optimal corners and then stopping there is room to make a perfect test in what the alignment won't be influential.

    It is not necessary to adjust the camera controls, just by checking focus (wide open) in the corners we can align the optical axis to be perpendicular to the target, based in the Scheimflug principle, for testing it is not necessary that the camera is extremly well aligned, if we align the optical axis for the film plane then the test is good enough.

    With 130mm test DOF at 6m we need an accurate job in the test, but those 130mm allows room enough to make a perfect test.

    I made several personal tests and I found that aligment is no problem, also we may focus again for each spot of the circle, making additional shots, to find if the result changes or not.

    Today, for personal tests, best if focusing again for each spot (Center-Mid-Corner), using a DSLR body in the back of the LF camera, this removes the field curvature and alignment factor. The lens field curvature of modern lenses may be irrelevant in practical photography, but it's good to remove that factor from a test.
    Attached Thumbnails Attached Thumbnails arne.jpg  
    Last edited by Pere Casals; 9-May-2019 at 06:03. Reason: CoC calculation added

Similar Threads

  1. lens spacing, front/rear using shims
    By Jac@stafford.net in forum Lenses & Lens Accessories
    Replies: 10
    Last Post: 11-Dec-2017, 20:14
  2. Replies: 1
    Last Post: 4-Jun-2012, 13:28
  3. Rodenstock 150 Apo-Sironar-S lens shims
    By Dave Jeffery in forum Lenses & Lens Accessories
    Replies: 17
    Last Post: 9-Oct-2009, 14:35
  4. Measuring shims - inquiring minds
    By Steve Goldstein in forum Lenses & Lens Accessories
    Replies: 0
    Last Post: 15-May-2009, 15:21
  5. shims for apo-germinar?
    By Craig Wactor in forum Cameras & Camera Accessories
    Replies: 7
    Last Post: 19-Jul-2005, 15:54

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •