Thread: I call Hot Rod Cameras Bluff with a $10,000 Bet (for Sharpest PL RF for Komodo)

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  1. #221  
    Senior Member Satsuki Murashige's Avatar
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    Quote Originally Posted by Björn Benckert View Post
    The reason for digiprimes being user adjustable is
    1. they came out when mounts for 16mm digital cameras where all over the place.
    The Zeiss DigiPrimes were B4-Mount lenses for 3-CCD cameras, not single chip 16mm sensor cameras. All B4 lenses had back-focus adjustment, due to the variable quality of those mounts. Only the high end cameras like the F23 had stainless steel mounts, cheaper cameras had aluminum mounts. And B4 mount was not as rugged as PL, much smaller flanges. It makes me shudder to think how we used to put those large front heavy B4 zooms on that mount without any lens support.
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  2. #222  
    Quote Originally Posted by Satsuki Murashige View Post
    The Zeiss DigiPrimes were B4-Mount lenses for 3-CCD cameras, not single chip 16mm sensor cameras. All B4 lenses had back-focus adjustment, due to the variable quality of those mounts. Only the high end cameras like the F23 had stainless steel mounts, cheaper cameras had aluminum mounts. And B4 mount was not as rugged as PL, much smaller flanges. It makes me shudder to think how we used to put those large front heavy B4 zooms on that mount without any lens support.
    The 3CCD´s also came with more energy consumption and more heat which add to the problem.
    Björn Benckert
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  3. #223  
    Senior Member Adrian Jebef's Avatar
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    this is a great thread. lots of fun. some quick thoughts:




    even those of us with decades of experience in motion picture photography don't quite realize how important proper collimation is.

    even those of us who do realize its importance still struggle to discern if it was done successfully.

    sometimes the ability to achieve proper collimation is compromised by: the method, the machinery, the camera, the lens, and/or the individual.

    close is usually "close-enough".





    collimation is two things: proper camera mount spec and proper lens mount spec.

    IMO the camera body mount must ALWAYS be at spec.

    IMO the lens mount must ALWAYS be at spec.

    IMO a lot of the time they aren't.

    shims exist for a reason. that reason is to get both the camera and the lens back to spec when they are out of spec.

    if collimation is off, even slightly, especially on the camera body, your image will be noticeably softer.

    when collimation if off your lens does not perform "just as good but with focus marks not accurate"; your lens may simply NOT PERFORM; ie the image sharpness is complete garbage

    maintaining and trusting proper collimation should be done via technical measurement and adjustment and via review of the photographed image

    lenses play a HUGE role in maintaining and discerning proper collimation. old lenses, anamorphic lenses, beaten and bruised lenses even when "properly" collimated might reproduce less than ideal results. this is why I recommend shimming (+/- from 52mm PL spec) the lens before fooling with the camera body.

    sharp wide lenses like a Zeiss 21mm Master Prime are excellent lenses to use for critical collimation checks





    i think any type of PL Mount camera body lens adapter with user adjustable collimation would be great. as long as it is robust and serviceable
    Adrian Jebef
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  4. #224  
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    Quote Originally Posted by Adrian Jebef View Post

    sharp wide lenses like a Zeiss 21mm Master Prime are excellent lenses to use for critical collimation checks
    Only if you know it’s collimated properly in the first place. And how do you know that day in and day out if you’re out in the field using it?

    The most excellent way to check a camera isn’t to use a lens, but to use a FFD checking device like the DENZ FDC. https://www.denz-precision.com/en/cinetec/fdc-multi/

    Using a lens to check a body is where errors come from.

    JB
    John Brawley ACS
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  5. #225  
    Senior Member Jacek Zakowicz's Avatar
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    Prime lenses usually do not get softer when the back focus is off. Same goes for the camera flange. The main issue is that if they are "long" (image forms in front of the sensor ) you will never reach infinity focus. It used to be more crucial when scale calibration was used by the AC to follow focus. I don't see much of that now- it gave way to pulling focus off monitors. But we mainly work with vintage optics so the contemporary lenses may be different. Zooms (lose parfocality but still as sharp) and anamorphics are quite sensitive to back focus and flange so that's a different story.
    Back in my rental house days the camera tech kept a hero lens in their shop used exclusively to collimate film camera view finders. They were comfortable with the procedure and did outstanding job keeping the flange depth on point. Now with the test devices it may be easier but the old habits die hard. I bet there are quite few with hero lenses used every day .
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
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  6. #226  
    Moderator Phil Holland's Avatar
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    Quote Originally Posted by Jacek Zakowicz View Post
    Prime lenses usually do not get softer when the back focus is off. Same goes for the camera flange.
    This is a fascinating statement that I don't think many optical engineers would agree with, PHD or not.

    Longer lenses typically would observe less of the behavior due to typical designs. But I'd say it's pretty observable 85mm and wider in most cases.

    There are lenses that exhibit less of an issue when things are off, mainly due to telecentricity, but still measurable divergence.

    Grabbing something like an 18mm Master Prime, this is pretty easy to test. Grabbing something a bit more forgiving less so.

    One of the reasons vacuum plates were used in 70mm camera heads was to combat the image plane from being uneven, which was/is visible in projection when something goes wrong, i.e. uneven focus across plane. Less of an issue on smaller formats as the rigidity of film stands up better, but nonetheless a rather visible issue.

    I only know about this due to working on those style of productions and using the Solitaire with 70mm head featuring a vacuum within the gate and the critical nature of ensuring the flange was on point. Same thing done actually with the attenuators in laser recorders to achieve critical focus.

    All optics. All important.
    Phil Holland - Cinematographer - Los Angeles
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  7. #227  
    Senior Member Jacek Zakowicz's Avatar
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    Quote Originally Posted by Phil Holland View Post
    This is a fascinating statement that I don't think many optical engineers would agree with, PHD or not.

    Longer lenses typically would observe less of the behavior due to typical designs. But I'd say it's pretty observable 85mm and wider in most cases.

    There are lenses that exhibit less of an issue when things are off, mainly due to telecentricity, but still measurable divergence.

    Grabbing something like an 18mm Master Prime, this is pretty easy to test. Grabbing something a bit more forgiving less so.

    One of the reasons vacuum plates were used in 70mm camera heads was to combat the image plane from being uneven, which was/is visible in projection when something goes wrong, i.e. uneven focus across plane. Less of an issue on smaller formats as the rigidity of film stands up better, but nonetheless a rather visible issue.

    I only know about this due to working on those style of productions and using the Solitaire with 70mm head featuring a vacuum within the gate and the critical nature of ensuring the flange was on point. Same thing done actually with the attenuators in laser recorders to achieve critical focus.

    All optics. All important.
    I'm not sure I understand. This is simple physics: As the object moves closer to the lens the image behind the lens moves further. Therefore the nodal point of the lens has to move further from the focusing plane to compensate. This is how focusing works on spherical lenses. If it worked any different you couldn't follow the object. Whether it is internal focusing or the whole optical block is moved it does not matter- the laws of physics still apply...
    BTW that's how "breathing" occurs- the lens moves closer to the film/sensor plane and produces the "dolly" effect...
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
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  8. #228  
    Moderator Phil Holland's Avatar
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    Quote Originally Posted by Jacek Zakowicz View Post
    the laws of physics still apply...
    Exactly what I'm saying.
    Phil Holland - Cinematographer - Los Angeles
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    2X RED Monstro 8K VV Bodies, 1X RED Komodo, and a lot of things to use with them.

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    Red Dragon
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  9. #229  
    Senior Member Adrian Jebef's Avatar
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    Quote Originally Posted by John Brawley View Post
    Only if you know it’s collimated properly in the first place. And how do you know that day in and day out if you’re out in the field using it?

    The most excellent way to check a camera isn’t to use a lens, but to use a FFD checking device like the DENZ FDC. https://www.denz-precision.com/en/cinetec/fdc-multi/

    Using a lens to check a body is where errors come from.

    JB





    JB yes of course.

    You collimate the camera body. Then you collimate the lens. Then you put the lens on the camera and double check critical infinity focus via a large monitor.

    My point is that certain lenses (like the wide Master Primes) can be very telling in regards to proper collimation. Even incredibly slight deviations can create noticeable loss in performance. A big part of the process is simply noticing by eye what proper and improper collimation looks like. Assuming it looks like out of focus vs in focus misses the subtly.
    Adrian Jebef
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  10. #230  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by Adrian Jebef View Post
    when collimation if off your lens does not perform "just as good but with focus marks not accurate"; your lens may simply NOT PERFORM; ie the image sharpness is complete garbage
    This is interesting. I assumed improper collimation would still create sharp images, but the focus marks would be out and you might not be able to reach infinity. How do you explain the use of extension tubes for macro photography? These put the back focus waaaay out, but can still produce sharp images AFAIK. Is the loss of sharpness small enough to make the trade-off worthwhile in this case, or are certain lenses more forgiving when it comes to back focus?
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