Thread: New to Cine Lenses (focus markings off?)

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  1. #1 New to Cine Lenses (focus markings off?) 
    I just bought a used set of cine primes (Canon CN-E 14, 24, 35, 50, 85, and 135) from LensAuthority.com. These are the first cine lenses I've owned. I've been playing around with these and think they may need some calibration, but am not sure.

    How accurate are the focus distance scales supposed to be? I've heard very accurate... which makes me think these are off.

    With the camera stationary, I am measuring from the sensor plane to a point in focus directly in front of the lens, and I'm finding the focus markings on the lenses to be off, sometimes by a few inches. The 50 seems to be dead on though.

    Is it common for cine primes to go out of 'calibration'? Is it something that can be corrected? I'm a CPS Platinum member and am thinking about sending them in to be looked at, but figured I'd ask around first.

    The lenses were advertised as being in 'excellent' condition, and they appear so - the glass is flawless, and the housings show no dents, dings, scrapes, or other signs of abuse. Being new to cine lenses, I guess I'm just not sure what to expect. Perhaps I'm not even testing them correctly.

    Any insight or advice is appreciated!
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  2. #2  
    Senior Member Michael Lindsay's Avatar
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    How do you know if your cameras back focus is correct?.. also are you near a proper hire house?

    Sorry to ask questions but it is a can of worms if you dig too deep... my guess is your lenses are probably ok but in my opionion any lens with a generic scale is only likely to be ok... also what stop you checking at?
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  3. #3  
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    You need to find a technician and collimate them to your camera in order to be able to use the marks accurately, as Michael said you might have to check your cameras back focus as well, it's not a big deal (also checking the lenses since you got them used wouldn't be a bad thing). In addition, EF mount depending on the camera isn't exactly the most accurate mount and has flex (Cine cameras EF mounts are usually ok and lockable, but dslr/mirrorless/etc are off one way or the other). The most practical approach is to put your own marks on a piece of tape (also make sure you can hit infinity with all lenses)
    Last edited by Jason Mavrokefalos; 12-17-2018 at 04:03 PM.
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  4. #4  
    Senior Member Nick Morrison's Avatar
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    Quote Originally Posted by Matthew Macomber View Post
    I just bought a used set of cine primes (Canon CN-E 14, 24, 35, 50, 85, and 135) from LensAuthority.com. These are the first cine lenses I've owned. I've been playing around with these and think they may need some calibration, but am not sure.

    How accurate are the focus distance scales supposed to be? I've heard very accurate... which makes me think these are off.

    With the camera stationary, I am measuring from the sensor plane to a point in focus directly in front of the lens, and I'm finding the focus markings on the lenses to be off, sometimes by a few inches. The 50 seems to be dead on though.

    Is it common for cine primes to go out of 'calibration'? Is it something that can be corrected? I'm a CPS Platinum member and am thinking about sending them in to be looked at, but figured I'd ask around first.

    The lenses were advertised as being in 'excellent' condition, and they appear so - the glass is flawless, and the housings show no dents, dings, scrapes, or other signs of abuse. Being new to cine lenses, I guess I'm just not sure what to expect. Perhaps I'm not even testing them correctly.

    Any insight or advice is appreciated!
    The markings should line up. This is why it's advisable to buy cine glass from either Duclos or Abel, as they service the glass before they sell it to you. I don't know of anyone else that does that.
    Nick Morrison
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    smallgiant.tv
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  5. #5  
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    Highly recommend the use of a tool like this to set the Back Focus of your Red when the EF mount is on it, you can then set your lenses to the camera body, or have them collimated at a shop like Duclos:

    https://denz-deniz.com/en/premium-products/fdc-multi/

    Disclaimer : Atlas Lens Co. Is a USA reseller for the Denz tools - so you're welcome to inquire with us for purchase.
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  6. #6  
    Senior Member Blair S. Paulsen's Avatar
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    As noted above, the distance markings on cine lenses don't mean much unless your back focus is dead nuts accurate. Even then, minor variations between lenses in a set are one key reason rental houses typically have a prep bay for the AC to chart offsets.

    Cheers - #19
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  7. #7  
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    My suggestion is to set your 14mm at infinity wide open and check image quality at a distant thin object such as a power line wire. If under magnification the image is sharp, your back focus is probably correctly set. If it is not sharp, it could be the lens or back focus. Next try the 24 at infinity without moving the camera. Same thing with the 35. if the images seem like they get progressively closer to focus with the 35 than the 14, most likely back focus. If , say the 14 is soft, 24 sharper and then 35 goes soft and maybe your 50 is sharp as you say, then the lenses may need attention. All lenses should be eveluated wide open as it is quite important.
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  8. #8  
    Senior Member Jeffery Anderson's Avatar
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    Quote Originally Posted by Matthew Macomber View Post
    How accurate are the focus distance scales supposed to be?
    you need to test each individual set of lenses.

    the quality of the build will help the lens from shifting focus over a period of time, but you're going to test and adjust any set of lenses and each individual lens
    I have to try and change the landscape, whatever it is.
    -Robert Plant
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  9. #9  
    Senior Member Michael Lindsay's Avatar
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    Notes that I think are relevant...

    Wide open the CNE primes clearly focus different parts of the spectrum at different depths
    I believe Red's focus tool works off the green photo sites only. This means the colour neutral best focus point is different from what you will subjectively pick as sharpest focus using the Red's focus mode
    CNE primes use generic scales (as do Sigma, Tokina etc). This mean you need to be lucky for every focus mark to line up. It also means setting the lenses up for infinity can be an issue closer in. I would agree with Vance if these where cooke or Arri lenses but you may have to be a little more flexabile..
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  10. #10  
    Senior Member Jacek Zakowicz's Avatar
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    Quote Originally Posted by Michael Lindsay View Post
    Notes that I think are relevant...

    Wide open the CNE primes clearly focus different parts of the spectrum at different depths
    I believe Red's focus tool works off the green photo sites only. This means the colour neutral best focus point is different from what you will subjectively pick as sharpest focus using the Red's focus mode
    CNE primes use generic scales (as do Sigma, Tokina etc). This mean you need to be lucky for every focus mark to line up. It also means setting the lenses up for infinity can be an issue closer in. I would agree with Vance if these where cooke or Arri lenses but you may have to be a little more flexabile..
    I think the last part is definitely valid- you will see variations in accuracy of the focusing marks if lenses are not marked and engraved individually. Or, as Zeiss does it, have a few variations of the scales and install the closest.
    As far as focusing different colors (parts of the spectrum) differently for all practical purposes is not true with modern lenses. All proper focusing tools focus on the green because it is nearest to the sharpest image. No need to worry about that....
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
    Professional Broadcast and Digital Cinema Equipment
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