Thread: Focus problems with my Dragon after upgrade

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  1. #1 Focus problems with my Dragon after upgrade 
    Senior Member Christoffer Glans's Avatar
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    I started a thread in the lens section about my Sigma 35mm not being able to focus properly. Now it seems that's not the case. Since then I've tried the Canon CN-E, and they showed the same thing; a focus that is never really in focus with a horisontal smeared "bokeh" that changes to a vertical "bokeh" when going past the focus point. I took my Dragon to an experienced camera and lens technician at the local rental house and we adjusted the backfocus with his gear. Still the problem continued. We tried both the Canon CN-E primes, the Sigma lens, changed the mount to a PL and tried out the Ultra Primes and it's the same all the time.

    Here's the Canon 24-70 and the Sigma 35mm. (In the end is the Sigma and that shows the problem best).
    Sigma download

    Here's a video from when we did tests at the rental house. First one is a Canon CN-E and second is an Ultra Prime. Last one is Canon CN-E 85mm outside, the red highlight in the window shows the strange smearing of the focus when pulling focus.
    CN-E and Ultra Prime test download
    (Download takes a few sec to start)

    EDIT:
    Uploaded the one I shot with the technician to Vimeo.
    https://vimeo.com/141118180
    Password: sharp

    Has anyone encountered this? I've sent word to my rep at Red London, so I'm hoping I get som info there, but this is serious if this went through QC when I upgraded to Dragon. It's visible on full images as making the bokeh close to the sharp plane look smeared and ugly.
    "Using any digital cinema camera today is like sending your 35mm rolls to a standard lab. -Using a Red is like owning a dark room."
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  2. #2  
    Quote Originally Posted by Christoffer Glans View Post
    I started a thread in the lens section about my Sigma 35mm not being able to focus properly. Now it seems that's not the case. Since then I've tried the Canon CN-E, and they showed the same thing; a focus that is never really in focus with a horisontal smeared "bokeh" that changes to a vertical "bokeh" when going past the focus point.
    If you've played with Canon T-S lenses, you know that the horitzontal->vertical bokeh is a characteristic of a tilt. My guess is that either your sensor or your lens mount, or both, are adding tilt where you don't want it.
    Michael Tiemann, Chapel Hill NC

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  3. #3  
    Senior Member Christoffer Glans's Avatar
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    Quote Originally Posted by Michael Tiemann View Post
    If you've played with Canon T-S lenses, you know that the horitzontal->vertical bokeh is a characteristic of a tilt. My guess is that either your sensor or your lens mount, or both, are adding tilt where you don't want it.
    Exactly my theory also. Because we changed mounts and got the same result, it must be the sensor. Or could it be something with the OLPF? I haven't touched it or changed it. It has been the STH since I got the camera back from the upgrade.
    "Using any digital cinema camera today is like sending your 35mm rolls to a standard lab. -Using a Red is like owning a dark room."
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  4. #4  
    Quote Originally Posted by Christoffer Glans View Post
    Exactly my theory also. Because we changed mounts and got the same result, it must be the sensor. Or could it be something with the OLPF? I haven't touched it or changed it. It has been the STH since I got the camera back from the upgrade.
    You could take the OLPF out completely and eliminate that factor from the equation. It would obviously throw off color and you'd need to readjust back focus, but if the tilt remains, it's not the OLPF.
    Michael Tiemann, Chapel Hill NC

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  5. #5  
    Senior Member Jacek Zakowicz's Avatar
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    As the OLFP is a flat glass with no power it will have NO effect on any optical aberration- tilted or not
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
    Professional Broadcast and Digital Cinema Equipment
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  6. #6  
    Senior Member Christoffer Glans's Avatar
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    Then, this is a sensor issue then, if it's not the mount, not the lenses and not the OLPF, then the only thing left is that Red mounted the Dragon sensor wrong or off. Can't think of anything other than this.
    "Using any digital cinema camera today is like sending your 35mm rolls to a standard lab. -Using a Red is like owning a dark room."
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  7. #7  
    Moderator Phil Holland's Avatar
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    Can you upload this video to Vimeo with a download link or Dropbox? Both zips came in as corrupt for me. There's a few things it can be.
    Phil Holland - Cinematographer - Los Angeles
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  8. #8  
    Moderator Phil Holland's Avatar
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    Just do a magnified export of the effected area.
    Phil Holland - Cinematographer - Los Angeles
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  9. #9  
    Senior Member Christoffer Glans's Avatar
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    Quote Originally Posted by Phil Holland View Post
    Just do a magnified export of the effected area.
    I did.
    Uploaded the one I shot with the technician to Vimeo.
    https://vimeo.com/141118180
    Password: sharp


    It's not "an effected area", it's the entire image. The focus plane never gets into focus and has a smeared bokeh close to it, different directions based on if it's bokeh past the point of focus or before it. On larger images it looks like details are smeared. A "circular detail" in the image will scew and smear either horizontally or vertically instead of just "blooming" out of focus.
    "Using any digital cinema camera today is like sending your 35mm rolls to a standard lab. -Using a Red is like owning a dark room."
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  10. #10  
    Moderator Phil Holland's Avatar
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    Quote Originally Posted by Christoffer Glans View Post
    I did.
    Uploaded the one I shot with the technician to Vimeo.
    https://vimeo.com/141118180
    Password: sharp


    It's not "an effected area", it's the entire image. The focus plane never gets into focus and has a smeared bokeh close to it, different directions based on if it's bokeh past the point of focus or before it. On larger images it looks like details are smeared. A "circular detail" in the image will scew and smear either horizontally or vertically instead of just "blooming" out of focus.
    Did that technician mention words like "coma, astigmatism, or spherical aberrations"? Center frame it appears to be doing what I would expect for the given lenses. I'm assuming this was wide open for all of these? Did you test T4 or T5?
    Phil Holland - Cinematographer - Los Angeles
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    Red Weapon/DSMC2
    Red Dragon
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