New to Cine Lenses (focus markings off?)

[Matthew Macomber]

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!

 

[Michael Lindsay]

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?

 

[Jason Mavrokefalos]

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)

 

[Nick Morrison]

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.

 

[Dan Kanes]

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.

 

[Blair S. Paulsen]

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

 

[Vance Colvig]

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.

 

[Jeffery Anderson]

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

 

[Michael Lindsay]

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..

 

[Jacek Zakowicz]

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....

 

[Matthew Macomber]

Everything you all have shared is very helpful, thank you.

Optically, the lenses seem great and I have no problem hitting infinity, although I've noticed on a couple of these lenses that true infinity is past the infinity mark. I should do more tests and write down exact findings for each lens.

I shoot on everything from Red to Blackmagic to DSLR, so I can't exactly have the lenses 'matched' to a specific camera body. I'm okay with the marks being off, as long as that is normal for lenses at this level, which it sounds like it is according to you guys. I just didn't know what to expect. Even if the focus scales can't be dead on, I'm still glad to have the consistent color, unified housing size, manual iris, and long smooth focus throw.

So... when you rent a camera and lenses from a proper cine rental house, a technician will adjust the lenses to match the camera prior to sending out the whole package? Or no? Are the adjustments relatively common practice? I wonder if perhaps someone can take these lenses back to 'baseline' for me.

 

[Jacek Zakowicz]

Lenses shouldn't be matched to a camera body. If both the lenses and the camera body are adjusted according to the proper standards any lenses will work properly with any camera body. That's what standards are created for. Rental houses have it under control because they usually have professionals maintaining the equipment and (the rental houses) have done it for as long as they are in business. It does not work any other way for them. Owner operators do not usually have the resources to assure proper maintenance so it is a bit of a hit and miss... That however may or may not be relevant to the OP scale calibration issue...

 

[Michael Lindsay]

..afraid I disagree...unless you only shoot with a very small subset of modern glass (sumilux-c, signature primes etc) axial chromatic aberration is present and occasionally a real issue.... and focusing using focus tools when wide open can leave a magenta bloom... seen it even with a Masterprime 100mm. From my limited experience of CNE primes they are far from clean from axial CA...

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....

 

[Michael Lindsay]

Matthew ... from my limited experience with CNE primes I fee you should be able to get close enough to work with the lenses off the barrel... good luck!

 

[Jacek Zakowicz]

..afraid I disagree...unless you only shoot with a very small subset of modern glass (sumilux-c, signature primes etc) axial chromatic aberration is present and occasionally a real issue.... and focusing using focus tools when wide open can leave a magenta bloom... seen it even with a Masterprime 100mm. From my limited experience of CNE primes they are far from clean from axial CA...

With all due respect Michael- Chromatic aberration has nothing to do with shifting back focus, you can still find the sharpest image with or without it. Obviously all lenses exhibit it to some degree. That has nothing to do with the focus scale calibration...

 

[Phil Holland]

There is a larger issue at play. Actually a couple.

First. And without naming names. Some manufacturer's tolerances for accurate scales is fairly low. And interestingly there's a fairly active effort from certain professionals to help get this sorted.

Second. Some lenses are dialed into other cameras due to variance in OLPF and cover glass thickness/properties. The Zeiss Supremes are a very good example of this when it comes to precise scales.

Purchasing your lenses from a reputable vendor can help with this. Additionally having your lenses serviced and also ensuring your camera's back focus is set correctly is rather important.

I agree, most owner operators don't touch any of this or even think of it until it bites them. But that is as they say, part of the journey.

 

[Michael Lindsay]

Just noticed this... not sure you follow what I have said.... I know you are not a camera guy but if you grab a red and find focus wide open on a fast prime (with axial CA) with and without the focus tool and check the barrel...

With all due respect Michael- Chromatic aberration has nothing to do with shifting back focus, you can still find the sharpest image with or without it. Obviously all lenses exhibit it to some degree. That has nothing to do with the focus scale calibration...

 

[Jacek Zakowicz]

Just noticed this... not sure you follow what I have said.... I know you are not a camera guy but if you grab a red and find focus wide open on a fast prime (with axial CA) with and without the focus tool and check the barrel...

Focus tool is just that- a focus tool. Operator must know how to use it and part of that knowledge/competence is knowing the tool limitations. I've been perfecting my craft for 32 years and still am every day. If I relied on my tools blindly I would be out of business long time ago. That is exactly what makes me the expert in my field and what makes my customers come back. I know you are very well aware of all that Michael as you are the expert in your field so I'm a bit puzzled with your post ;-)