Flange distance and back focus?

Another email from Canon re this.

The lenses are set up in japan using the correct back focus, and therefore this will give you the correct focus position on the lens. If you were to alter this for another camera then put that lens on to the C500 etc the back focus would be incorrect so you would have to adjust it again.
If you wish to adjust your lenses then that is your choice. But the lenses are correct for the EF mount back focus position.

This backs my earlier expectations that the primes are set up properly and unlikely to be out as they are factory set with no Canon provision for adjustment and a recommendation they shouldn't be.

So according to Canon I can use these lenses on their professional cameras and any camera with the correct mount dimensions.
I would guess Canon have had few complaints about lenses that cant focus to infinity on their professional camera lineup.
I have to now consider what JB has said against what Canon are saying and I really cant see how Canon could get away with selling pro unshimmable primes with pro cameras and get away with it to the point they could give me that response.

This has to be another error on BM's part who altered the mount in order to please less than professional lens users. Although understandable it also catches out those who took them at their word that the camera was professional.

One way to test for sure, try it on a canon pro body.

Tom

If I had one I would. However surely Canon wouldn't be misleading me here. What do you think?

Mark.

You keep harping about being professional.

It's is standard professional operating practice to check and if necessary, collimate (shim) the lenses or body or both you're using for a given camera body. Even if it's a one day job.

I've told you this previously. I also said it was "more likely" that they will be more accurate on another camera but the whole point of our discussion is that lenses need to be optimized to each camera anyway. Canon aren't disputing me.

It's very normal to shim lenses for a camera for each job.

Canon have actually supported this theory in their email to you. They have said if you collimate your lenses you would have to adjust them again for the new body. Yes. You would.

So.

The simple test, which you disparaged in the first place is to try your lenses on another EF mount body.

I dare you to get three different canon EF bodies and tell us how the witness marks line up, especially the wides.

I'm 99% certain they won't.

I'm sure you'll then go back to Canon right ? Demand they "fix" their bodies ?

I know they won't line up because that's well established fact. Canon vary their FFD from body to body and they can't be adjusted. This is exactly why BM changed their specs in the first place.

This is why EF kind of sucks balls as a cine mount. But it hasn't stopped thousands of people using it for exactly that purpose.

Interesting too don't you think that Canon tell you that you can't adjust or re-shim the lens and then contradict themselves in your second post and say that you can adjust them but that's your choice.

Are Canon LIARS ? They told you it can't be done then inferred it was your choice if you wanted it done.

You're being incredibly myopic. Do two things for me.

1. Test your primes with three other canon EF mount bodies and see if they all line up perfectly.
2. Go to a large independent local (not Canon) camera rental company that rents CN-E lenses in EF mount and ask them about collimator your lenses to your body. Make sure they have a "lens collimate" and a lens technician.

JB

Good find, Geoff. Interesting read.

Phil knows his stuff to, is the best person to go drinking with, and really wows me with all the knowledge he has collected. And yes, EOS mounts are one of the worst things ever. I only recommend people to buy EOS lenses because, well so many cameras use the mount these days, it's almost becomming the "new pl" which is a pity, and a PITA.

New email from Canon

With regards the EF mounts on the prime lenses, they will be correct for every type of Canon EF mount camera. I was only giving an example of the Canon 5D, C500. The lens back focus will be correct for any EF Canon camera.

Another message from Canon.

If you can find out the following information as Canon in Japan has asked for it.

1) Can you find out the specification of the Black magic camera for the EF mount?

2) Is there any adjustment on the mount on the camera side?

I am more than happy to check your lenses for you.

So BM? Can you give this info?

There is one 'fact' brought up here, I'd like to address:
Adam Roberts and John Brawley have written that the mount has to be adjusted in the 1/1000th of a millimeter. After reading that - and having an engineer's degree - I was questioning myself if that could be possible? Such a tight tolerance - I couldn't believe that, because 1) it would be really, really expensive to produce with this precision and 2) just changing temperatures in the sun would render that adjustment null and 3) producing and mounting shims with a thickness of 0.001 mm (or 1 µm) would be almost impossible.

So I did a quick search across the net:
e.g. http://www.pure4c.de/dynasite.cfm?dsmid=105382

Looks like we are in the 1/100s and not in the 1/1000s
The thinnest shims seem to be at 0.0127 mm (or 12,7 µm).

Of course the PL mount itself has to be manufactured very precisely with very small tolerances like ~5 µm.

There is one 'fact' brought up here, I'd like to address:
Adam Roberts and John Brawley have written that the mount has to be adjusted in the 1/1000th of a millimeter. After reading that - and having an engineer's degree - I was questioning myself if that could be possible? Such a tight tolerance - I couldn't believe that, because 1) it would be really, really expensive to produce with this precision and 2) just changing temperatures in the sun would render that adjustment null and 3) producing and mounting shims with a thickness of 0.001 mm (or 1 µm) would be almost impossible.

So I did a quick search across the net:
e.g. http://www.pure4c.de/dynasite.cfm?dsmid=105382

Looks like we are in the 1/100s and not in the 1/1000s
The thinnest shims seem to be at 0.0127 mm (or 12,7 µm).

Of course the PL mount itself has to be manufactured very precisely with very small tolerances like ~5 µm.

True. I have an extra 0 in my post. The point was that the mount only needs to be out by the thickness of a sheet of paper for the focus markings to be off. A distance that is very easy to be out on a mass produced product. It is even easy to be out by 0.1mm on a mass produced mount.

That is why cine lenses, including the Canon CN-E, and PL mounts are shimable.

Thanks Robert for posting that. Adam that also ties in with my two pieces of thin tape on the mount having bought it back to what appears to be correct focus.

I have emailed BM support on behalf of canon regarding the exact specs of the BM mount. So far no reply.

Adam Also quick correction. CN-E prime lenses are not made to be shimmed according to Canon. Otherwise they would have shims in stock and a clear path to do this. They have given their reasons which I have posted here. They do have shims for the CN-E Zooms though.

Mark....

I've spoken to two cine lens technicians I know locally, just to check.

Both of them say it CAN be done for primes. Both them have done it.

I cant do anything else for you. You don't seem to want to do anything suggested other than talk to Canon and berate BMD.

By the way. Ask Canon what their FFD is. I bet they won't tell you. That's because it's not published anywhere. Like their lens protocols, they keep it secret.

Good luck.

JB.

Mark....

I've spoken to two cine lens technicians I know locally, just to check.

Both of them say it CAN be done for primes. Both them have done it.

I cant do anything else for you. You don't seem to want to do anything suggested other than talk to Canon and berate BMD.

By the way. Ask Canon what their FFD is. I bet they won't tell you. That's because it's not published anywhere. Like their lens protocols, they keep it secret.

Good luck.

JB.

What's the point of quoting the last posting without adding a single word to it?

Hi Mark,

I would be interested in your response to my post of May 6th at 1:13 a.m. I have had another response from BMD re flange depth.

If you like another brand to compare: RED has always made it possible to adjust flange distance.

The solution on the Red One was not perfect yet, but the new one on Scarlet and Epic is very good. And it's true that you needed to adjust after massive temperature changes in the Red One. The newer cameras have a very well thought out combination of materials in the mount making that unnecessary.

Plus, Red makes one of the best Canon EF mounts I know of: Titanium with very high precision and an extra ring to stabilize the lens in it, so it doesn't shift when touching it.

They seem to know a thing or two about these things by now…

Hi Mark,

I would be interested in your response to my post of May 6th at 1:13 a.m. I have had another response from BMD re flange depth.

Alastair

Is this what you meant?
Are suggesting that BMD market thicker mounts in say 0.0005” rises? If available which one would you choose?

If so I would choose the mount that brings the BM4K up to the measurements the originally made using the canon CN-E's as a template. Which is obviously going to be Canons EF mount

Alastair What response did you get?

Mark....

I've spoken to two cine lens technicians I know locally, just to check.

Both of them say it CAN be done for primes. Both them have done it.

I cant do anything else for you. You don't seem to want to do anything suggested other than talk to Canon and berate BMD.

By the way. Ask Canon what their FFD is. I bet they won't tell you. That's because it's not published anywhere. Like their lens protocols, they keep it secret.

Good luck.

JB.

John I have spoken to some lens rental firms in London but no one seems to do it. One firm that does all the high end lenses never bothered to get back to me. I'm concerned that if this was an answer at how much this would cost especially looking at their lens rental prices. Hopefully though with your help and Canons (Although not berating BM at all but they are saying nothing) there might be a solution.

Just really hope so.

No response from BM support so I cant report back to Canon and so have no choice but to take Canons word on this. It now looks as if the witness marks on Professional lenses will not work with BM cameras unless shimmed or used on other cameras. Unfortunately Canon do not provide shims for CN-E lenses because they expect their tolerances to be accurate and so not needed.

Also getting these lenses shimmed by a specialist lens firm is likely to be expensive and render the lens useless on cameras that have correct tolerances.

I personally am just in the middle of these arguments and all I want is to be able to use my CN-E lenses for the purpose I bought them Instead I find myself as the target for abuse or blame. Somewhere down the line the Customer is always right seems to have got confused with the customer is always wrong.

No response from BM support so I cant report back to Canon and so have no choice but to take Canons word on this.

OR you could you know, try it on another camera, like a Canon camera.

Careful Tom... He might think you are targeting with abuse and blame.

Careful Tom... He might think you are targeting with abuse and blame.

The only person I blame here is Canon, for selling such expensive precision lenses on such an imprecise cheap mount.

:-p

No response from BM support so I cant report back to Canon and so have no choice but to take Canons word on this.

OR you could you know, try it on another camera, like a Canon camera.

Well Like yourself who doesn't have a BM 4K camera I don't have a Canon camera. What I do have is a statement from Canon saying their mounts are all the same size and that's why the CN-E primes don't need shimming. I also know that BM have indeed shortened their EF Mounts to allow lenses that are out to focus to infinity and that is effectively throwing out all witness marks on my lenses which were designed to conform to the EF Mount spec Which is well known even if they don't publically release those figures.
I further know that the cost of re jigging and shimming my CN-E lenses will need to be done by a specialist lens rental firm that deal with professional gear and (If I can find one) is likely to be very expensive.
I also know that if I need to use a properly specced EF mount again that Canon says are accurate then I will need to reshim.
I further know that if the answers given on this thread are correct I will have to reshim my canon lenses everytime I want to change the camera.
I also know that BM originally designed their EF mount to match the Canon CN-E lenses and changed it so that other lenses could focus to infinity.
I also know as someone who wants to use lenses professionally IE using the witness marks I am in a minority of one and therefore insignificant.

Mark, I don't think you are a minority of one or insignificant. Your expectation seemed reasonable to me but the discussion has been an eye opener regarding the EF mount. I'm sorry that you've had these setbacks... Now I think the more prudent option would seem to be the URSA PL. If it lives up to our expectations and the description on BMD's web pages.

Or maybe these high-end lenses are just out of my league and I should go with the SLR Magic Anamorphot on the BMCC MFT or Pocket with Metabones Speed Booster.

Edit: I must have been tired when I wrote the 'downer' comments so I removed them.

Rick Lang
Sent using Tapatalk HD

I think it's a fault to consider the EF mount for any serious cine lenses at all. I've seen EF mounts on Canon's own cameras all over the place, the same lens (from Canon, not Tokina stuff) had different infinity points on different cameras. Plus, there is enough play in the mount to make the image shift when you touch the lens, not even speaking of using a FF.

The only ones who got their EF mount right is RED, but even then, with their very precise and expensive Titanium mount with an extra locking ring, you'd need to collimate for your individual EF lenses. I have to admit that I never tested Canon cine lenses on a RED, since I rely on PL mount for serious work, but they might be spot-on among them once the camera has been adjusted.

Uli

I think if that is the case it would be Canons cheaper stuff for stills cameras that use autofocus.

Canon released their Cinema line in Hollywood and deliberately set out to create a professional lineup even though they used 8 bit 4.2.2 camera's After talking with Canon who say the CN-E Primes don't need shimming and they don't carry or make shims for them because they are designed to work on their pro equipment. I imagine the tolerances for these would be spot on. Be nice to hear from some C500 or C300 1DC users using Canon professional lenses like the CN-E's and see what their experience is.

Uli

I think if that is the case it would be Canons cheaper stuff for stills cameras that use autofocus.

Canon released their Cinema line in Hollywood and deliberately set out to create a professional lineup even though they used 8 bit 4.2.2 camera's After talking with Canon who say the CN-E Primes don't need shimming and they don't carry or make shims for them because they are designed to work on their pro equipment. I imagine the tolerances for these would be spot on. Be nice to hear from some C500 or C300 1DC users using Canon professional lenses like the CN-E's and see what their experience is.

I have rented the c300 a few times for short doc/talking head work. I did use CN-E primes once (24 and 50). We had the lenses tested on the camera and the 24 was slightly out, all of the witness marks were out from 6 inches to a few feet at the end.

This is not a fault of canon's lenses in particular, its just the way lenses work. They wear down, shifting ever so slightly from being put on and off over and over. The canon rep you were talking must be mistaken or has misunderstood your question regarding shimming canon lenses. Ive even had to shim Ultra Primes (way more expensive then canon) in the past, so if canon claims that they've figured out how to never need to shim their lenses Id love to hear how.

However it wasnt a big deal, the assistant at the rental house shimmed our lens for us and we were good to go, witness marks perfect for the whole shoot. Hope this helps

Canon released their Cinema line in Hollywood

Mark what does a statement like this even mean ? It's marketing speak. You give it status and credence by the fact you quote it. Hollywood is an endorsement. You've applied it to your own personal situation.

I've shot a film in "Hollywood", literally within sight of the sign. It was the lowest budget film I've ever worked on. It doesn't actually mean anything.

and deliberately set out to create a professional lineup even though they used 8 bit 4.2.2 camera's

Actually from memory the problem for canon was their stills division was suddenly outselling the video camera division in video camera camera sales with the 5dmk2.

Internally it was a problem for one division to be performing better than the division that was meant to be looking after that market. A stills camera was selling more than video cameras in the video camera market.

That's my understanding of how the "cinema eos" line came about.

The fact they chose 8b 4:2:2 shows they weren't very serious. Although it's good for what it is, it's probably the number one complaint about the canon cinema eos line.....everyone holds this against Canon.

nice to hear from some C500 or C300 1DC users using Canon professional lenses like the CN-E's and see what their experience is.

You must be meaning someone else then I guess....

I've used the C300, tested (but not used) the c500 and used the 1DC..

I still stand behind my views.

Mark you've bought into the emotion of the canon story. It's hard to face that it doesn't live up to your ideals.

About 18 months ago I bought my first Leica, a second hand M8, their first digital camera released in 2006. It's a mere 10 MP, has stuck pixels, a half sensor line mismatch, crappy DR, software that constantly crashes the camera and is useless beyond ISO 640 and has no OLPF and no IR filter at all. I just paid $4000 for a single 28mm f2 lens.

There's so many problems with it by so many measures and yet I've found the last 18 months have been the most personally rewarding of my photographic imaging pursuits. (All the file names with L are relevant)
https://www.flickr.com/photos/johnbrawley/

You just have to get past the sentiment of being "dudded" and get on with making it work. It's just gear and stuff. What matters is the end result and the process. Sometime limitations turn into gifts.

JB.

You just have to get past the sentiment of being "dudded" and get on with making it work. It's just gear and stuff. What matters is the end result and the process. Sometime limitations turn into gifts.

This is the best bit of advice to be posted on this forum in months.

Oh... And some really lovely images in you flikr stream John.

Had a reply from BM They build in a tolerance for their EF mount in comparison to other cameras. And it is expected the Witness marks on lenses will be out because of it.

This is in keeping with Canons claim their CN-E lenses will work fine with their professional cameras. It would be absurd if someone went out and bought a Canon C500 With CN-E primes and the witness marks were out and canons response was the lenses don't need shimming so we don't make any shims for them. Also by allowing this wide tolerance for lenses like the tokina It stops you focusing in close with the CN-Es And that's another problem that leaves a professional lens in the lurch.

But I swore off 4:2:0 because I know from experience, it doesn't always grade well.

Edit: Sorry this post is somewhat 'off topic' and a response to Rick's comment I found on a Forum search containing '4:2:0' but I'll add to this topic by emphasising one of the advantages of the MFT mount on some BM cameras is that you can use a Metabones 'Speed Booster' which not only adapts many excellent vintage SLR lenses such as my collection of Zeiss 'Contax' primes but the Metabones product also has a 'back focus' adjustment so my lenses are always spot-on, without shimming.

Given few HDMI recorders capture 50P, recording uncompressed 4:2:2 via HDMI is not an option so my solution when shooting with compressed 4:2:0 is to always fit a Schneider Optics 'Digicon' filter on front of the lens to 'compress' the light before it reaches the sensor. This conforms to an 8bit HD camera's 'sweet spot' of 2 stops above neutral grey and two stops below. Immediately transcode to 10bit ProRes 4:4:4 and in Post, you simply compensate for the Digicon with a minor Lift/Gamma/Gain adjustment. No burnt highlights, no banding, just great pictures. The following shots are 'field' grabs from an AVCHD stream shot through my Zeiss 600mm F4.0 with the Digiccon fitted:

Had a reply from BM They build in a tolerance for their EF mount in comparison to other cameras. And it is expected the Witness marks on lenses will be out because of it.

This wasn't unexpected Mark. I think we understand that this is the case already.

This is in keeping with Canons claim their CN-E lenses will work fine with their professional cameras.

I disagree and this hasn't been my experience or that of others here.

It would be absurd if someone went out and bought a Canon C500 With CN-E primes and the witness marks were out

And yet this is what peoples experience has been. You're saying it "would be" and we've seen evidence that that is indeed the case.

and canons response was the lenses don't need shimming so we don't make any shims for them.

And yet I've spoken to lens techs who have shimmed them, and so have others...

Also by allowing this wide tolerance for lenses like the tokina It stops you focusing in close with the CN-Es And that's another problem that leaves a professional lens in the lurch.

No Mark. Seriously mate, I've rebutted this many times with you already, it's misleading to keep bringing this point up. It's ANY EF mount lens that was wider than 50mm. They're ALL OUT, not just the Tokinas.

FFD issues show up more the wider the lens. The Tokina was a popular lens for those concerned about the crop factor of the BMCC sensor and were especially notorious for not hitting infinity even on Canon cameras, but it wasn't just them.

BM changed the EF mount tolerance to favour ALL EF mount lenses, and followed what Canon themselves have done with their stills cameras.

Furthermore, ALL CINE lenses need shimming over time. You're ignoring this fact as well, and render's Canon's own claim that their lenses don't need shimming misleading at best.

jb

Well John

According to BM When they adhered to Canons EF spec They got a lot of complaints that a lot of third party lenses didn't work and so they made allowances. Also there is no way BM will change the mount or adapt it in any way So were stuck with it.

I understand your argument when dealing with Pro equipment and mixing and matching that you need to get things calibrated. Obviously pro equipment gets used and abused as well as altered changed and used differently. What I don't accept is that Canon sell from new their more pro lenses and cameras that don't leave the factory exactly specced. I believe they do. That is why if I go out and buy CN-E lenses I expect them to work properly. Also their cameras to be exactly compatible. I don't think this is Canons fault I think it is third party manufacturers making wrongly specced lenses and BM catering moving down to that need So a compromise that leaves my pro lenses unable to focus at close range or working witness marks without shimming. BM have always said they want to help the masses Needless to say I am one of them and outreached myself buying these lenses and now stuck with it. However they are great lenses and my tape idea is working fine So not to bad after all. That's what a good DP does He finds a solution to all the millions of problems.

As for shimming my Canon lenses No way. I cant afford it and I don't want to devalue my gear and present your argument to the person who might buy my lenses on the second hand market.

Cheers.

Mark

I think if that is the case it would be Canons cheaper stuff for stills cameras that use autofocus...

Canon has just announced two new lenses, a modestly expensive $1,200 16-35mm F/4 IS and a much cheaper 10-18mm with ramping although that's the one they are promoting for videographers because it has STM supporting continuous auto-focus.

Rick Lang
Sent using Tapatalk HD

Well John

According to BM When they adhered to Canons EF spec They got a lot of complaints that a lot of third party lenses didn't work and so they made allowances. Also there is no way BM will change the mount or adapt it in any way So were stuck with it.

And this is a choice that very very vast majority of EF mount users would prefer. I know I would, even if I did have CN-E lenses.

I understand your argument when dealing with Pro equipment and mixing and matching that you need to get things calibrated. Obviously pro equipment gets used and abused as well as altered changed and used differently. What I don't accept is that Canon sell from new their more pro lenses and cameras that don't leave the factory exactly specced. I believe they do. That is why if I go out and buy CN-E lenses I expect them to work properly. Also their cameras to be exactly compatible.

I don't think you do understand.

The lenses DO work perfectly. There is no optical impact. They are the exact same lenses. All you're changing is a "calibration" to make sure witness marks would line up. Now you can CHOOSE to do that or not.

Many focus pullers will often mark up additional marks on a follow focus ring because a lens doesn't have fine enough marks. I know my focus pullers personally don't actually like the CN focus scales on the lens and much prefer the Angeniuex scale and "action"

It's entirely normal for a focus puller to totally ignore the focus scale on the lens anyway and start again with their own by meticulously marking up focus discs for the on and off side which they create themselves in pre.

Mark, you're still hung up that re-shimming a lens will "de-value" the lens. No one would be able to tell if you shimmed the lens to your camera and then shimmed it back to the EF mount ! Seriously, you're way over reacting to the "severity" of this issue. It just isn't as big a deal as you're making out because you're buying into this idea that the lenses and cameras come out the factory perfect and never in need of adjustment.

I don't think this is Canons fault I think it is third party manufacturers making wrongly specced lenses and BM catering moving down to that need So a compromise that leaves my pro lenses unable to focus at close range or working witness marks without shimming.

They certainly can focus at close range. it's just the witness marks won't be as accurate for your focus puller, who if they have done any time on set, will take it all in their stride....

As for shimming my Canon lenses No way. I cant afford it and I don't want to devalue my gear and present your argument to the person who might buy my lenses on the second hand market.

No one would blink who's worked with cine lenses before. Shimming your lenses doesn't de-value them at all.

JB

John,

The lenses are made to the canon EF specification Canon cameras are made to the EF specification When using Canon Lenses on Canon cameras there is no problem according to Canon.

BM Cameras were made the Canon Spec and changed it to their own Making third party lenses usable at the cost of throwing out witness marks and inability to use accurate specced lenses at close distances.

Where was this in BM's advertising literature? In fact BM advertised the opposite Showing nice CN-E lenses on their cameras. I believed them. No one warned or told me this. I found out after dumping £9000 on Canon lenses. There should be some sort of warning.

You're advice is this is normal
You're advice is shim the lenses because you think I can afford this.
You're advice is I'm over reacting.
You're advice is to make new marks on the focus ring that would be ineffective when focusing close.
You want to make this either my misunderstanding or my fault.

My advice to anyone out there with correct EF spec lenses is to use thin sticky tape. A focus chart and add layers until the marks tie up. Use it for the shoot then remove when storing the camera.

John,

according to Canon.

But not in the real world where my experience and those of others differs to what Canon are telling you Mark, when you actually don't have experience at all whatsoever.

BM Cameras were made the Canon Spec and changed it to their own Making third party lenses usable at the cost of throwing out witness marks and inability to use accurate specced lenses at close distances.

NO NO NO NO NO !

Mark how many freakin times do I have to say this. CANON MADE EF MPOUNT LENSES WHERE JUST AS "OUT" AS ANY OTHERS.

You're kind of pissing me off when you make me do a search looking these up when I told you it wasn't JUST tokinas.

viewtopic.php?f=2&t=9136#p58793
viewtopic.php?f=2&t=7266
viewtopic.php?f=2&t=4106#p27530
viewtopic.php?f=2&t=4319#p26521
viewtopic.php?f=2&t=4319#p26610

There are also many examples on the OTHER BM forums of the same problem Mark. Seriously mate

Where was this in BM's advertising literature? In fact BM advertised the opposite Showing nice CN-E lenses on their cameras. I believed them. No one warned or told me this. I found out after dumping £9000 on Canon lenses. There should be some sort of warning.

There's no need for a warning. Re-shim your lenses and they will work perfectly. They work perfectly now it's just that the witness marks are off, the same way they will be on just about an EF mont camera pro or otherwise you care to try them on.

You're advice is this is normal
You're advice is shim the lenses because you think I can afford this.

Then don't spend the money on lenses if you can't do what you need to do to make them work.... Have you bought the rest of the accessories that go with these lenses ? Some nice TRUE ND's ? Mattebox ? Rails and follow focus ?

You're advice is I'm over reacting.
You're advice is to make new marks on the focus ring that would be ineffective when focusing close.
You want to make this either my misunderstanding or my fault.

Yes Mark it is. You're still the only one that thinks it isn't normal practice to re-shim lenses. You're also the only one that hasn't worked using cine lenses before. Don't you think maybe that the ones that all have the experience that are telling you this might have a point ?

My advice to anyone out there with correct EF spec lenses is to use thin sticky tape. A focus chart and add layers until the marks tie up. Use it for the shoot then remove when storing the camera.

Terrible advice but you go for it mate.

I'm pretty tired of re-adressing the same points you're trying to score Mark. Yeah the EF mount sucks balls as motion imaging / Cinema lens moutn and this is a pretty exhaustive thread to discuss why, and you've dropped serious coin on some nice lenses that are still really nice and only need an "adjustment" to make all your problems go away. I've tried explaining "nicely" why you're wrong and you keep coming back with the same arguments that just don't don't every apply in any real world professional environment.

Good luck.

jb

The fact is John I can only go on what I'm told and Canon say different. It's no good blaming me if the big companies give us misinformation.
So your saying my Canon EF CN-E primes are out and not to the exact Canon spec Even though Canon have told me I am welcome to send my lenses into them and they will check that for free. They sound pretty sure of themselves don't they?

As I've said I do understand that professional lenses need shimming from time to time especially the higher end ones But even though my lenses are expensive they are not to the same level as Panavision for example. The CN-E lenses are marketed for high end consumer level. Yes as a DP you do have to do these things and many DP's don't own lenses or even cameras because these things are paid by the production company and not out of your own pocket. Its a different game asking a DP to pay for the lenses to be shimmed don't you think?

Mark, if you own a car or some road-legal vehicle please go out and look at the tires. Likely those tires and the rims they're mounted to are made to exacting specs: I mean, our very lives depend on them, right? In spite of these exacting tolerances, when those tires were mounted to those rims someone had to pay extra to have them balanced so they wouldn't wobble about. It's true you don't have to have tires balanced if you aren't expecting critical performance. But if you want them to work as expected, you pay extra to balance the tires.

I know what you're thinking, comparing crudely made tires and rims to fine pieces of photographic gear isn't accurate. But, knowing that EF mount system like I (and so many others here) do, the comparison isn't such a leap...

Simply put, the information you've gotten from Canon is incorrect. Are they intentionally lying to you? Not a chance. Are the people you're speaking with at Canon misinformed? Very likely. In this field, post-manufacturing adjustment is the way it works if you expect critical tolerances.

This isn't BM's - or anyone else's - fault. Right now your CN-E lenses do work on BM cams - just focus manually using a viewfinder. If you want critical performance you have to have your tires balanced. It really is this simple.

I guess none of this matters anymore The choices I have are plain and its up to me what I do with that I appreciate the discussion and although at times it may have been heated these issues are now resolved. We've heard Canons argument BM's argument and our resident Professional DP's experience and from all those arguments its up to me and those involved to extrapolate what's been said and make a decision. Mines made already. Gaffer tape has a new rival in the form of Brown tape.

The fact is John I can only go on what I'm told and Canon say different. It's no good blaming me if the big companies give us misinformation.

I'm not blaming you Mark. You're just not understanding why it can be normal to be in the position you're in.

So your saying my Canon EF CN-E primes are out and not to the exact Canon spec Even though Canon have told me I am welcome to send my lenses into them and they will check that for free. They sound pretty sure of themselves don't they?

Mark I'm not disputing the fact that your CN-E primes are shimmed to Canon's EF flange distance standard (which they don't publicly publish by the way).

That's precisely why your witness marks aren't lining up after all.

No ones arguing the spec. What I'm trying to make you understand is that if you want accurate witness marks for ANY cinema lens then you're very likely to have to re-shim the lens or the camera body.

What we're dealing with is reality, not what it should be according to a manufacturers, be they Canon or BMD.

Unfortunately with EF mount, unless you're shooting on a RED, this can't be done on the camera side. So if the camera is OUT then you're left with shimming the lenses to the camera.

The "defacto" standard introduced by your beloved can-do-no-wrong Canon means that that standard is short. Meaning even their own lenses won't line up on a camera. A fact you could very simply verify for yourself.

Its a different game asking a DP to pay for the lenses to be shimmed don't you think?

But Mark we don't make the rules do we ? You're wanting to use cinema lenses and that's great. This is just part and parcel of doing that.

And sorry to say again, but another reason you really should have looked at the CPs because they make it much easier for an owner operator. They've designed them to be re-shimmed by a user.

Or if you want the canons for their look (which you've said you do) then this is just the "cost" of making that choice.

JB

John,

My beloved Canon lenses? You are joking. The only reason I chose them was because they fitted the BM4K EF Mount (I thought perfectly). I've been patiently sitting on them since July 2013 waiting for the camera. Everything I did revolved around optimising BM's camera.

What you should refer to is my beloved BM4K camera and as much as I criticise its faults I love this thing. I also love that BM have shaken up the market. What I don't love is the lack of information and the fact that in their desire to help the masses get a stake they made the mount unfit for witness marks.

What I don't love is the lack of information and the fact that in their desire to help the masses get a stake they made the mount unfit for witness marks.

The EF mount was, and never will be, fit for witness marks. It was designed for a stills camera where the critical focus makes are not an issue.

Canon jumped on the 5D MK2 hype and produced the C300 then the C100 & C500. They used the EF mount as it made the transitions from the 5D easy. The C300 and C500 are also available in PL mount as they know that Pros who what an accurate mount would go for that.

Off the back of the success of the 5D they released the CN-E lenses. If you put those lenses on a 5D you will find the witness marks will be out. Even if Canon say they are perfect, they are not. The lenses might be totally perfectly in spec but there is so much variation in Canon EF mount on the cameras that even they have software in the camera to adjust the back focus of the EF lenses (as do Nikon).

Part of the cost of owning cine lenses is the fact that you'll need to calabrate them with the camera you intend using. As the EF mount can't be shimmed you have to shim the lenses.

I'm pretty sure you "could" shim the EF mount tho. On the BM cameras it's held in place by 4 allen hex nuts. Take those out and the mount plate pops off. You could get some custom shims made and correct the mount for your needs. I'm not encouraging people to remove their mount but if you have issues you could do that.

You tape trick is "shimming" the mount.

The issue tho is that the way the EF mount engages means that it would probably be out again within a few weeks of use.

What I don't love is the lack of information and the fact that in their desire to help the masses get a stake they made the mount unfit for witness marks.

And don't Canon do exactly the same thing ?????

They make cameras that have mounts that are out that can't be shimmed ? What's the difference ?

JB

I'm pretty sure you "could" shim the EF mount tho. On the BM cameras it's held in place by 4 allen hex nuts. Take those out and the mount plate pops off. You could get some custom shims made and correct the mount for your needs. I'm not encouraging people to remove their mount but if you have issues you could do that.

You tape trick is "shimming" the mount.

The issue tho is that the way the EF mount engages means that it would probably be out again within a few weeks of use.

This is what I've been trying to get done through this thread. I've asked BM but they wont. To much hassle I assume for one person.
Maybe a third party manufacturer could do this.

Whilst the debate was informative up to a point, may I suggest that you two get a room...then again, given the subject title....

This is what I've been trying to get done through this thread. I've asked BM but they wont. To much hassle I assume for one person.
Maybe a third party manufacturer could do this.

No. It's because you can't just add a random metal adaptor flange. Every single camera will be different. Every single set of lenses will be different.

You're not getting it. It's just not just a simple fix like this.

JB

JB

It wouldn't be random. BM originally set the mount to exactly Canons spec which although Canon have not released this info they know this information. All BM have to do is make a shim that fits the mount underneath the 4 hex screws that makes the mount exactly to the EF spec.

JB

It wouldn't be random. BM originally set the mount to exactly Canons spec which although Canon have not released this info they know this information. All BM have to do is make a shim that fits the mount underneath the 4 hex screws that makes the mount exactly to the EF spec.

A question for you Mark, how do you explain the fact that for every other lens maker of cine mounts - with even more precise and locked mounts than the EF mount, such as PL, - how is it that these still need calibrating due to natural variations, even when brand new - and yet the canon lenses magically are perfect and will apparently not require shimming or adjusting when used on a Canon made EF mount?

Putting aside the fact that several people have mentioned that they have used the same lenses, and found they needed adjusting also - how do you explain canon somehow being the exception?

Seems every thread in here goes downhill fast these days. JB and Tom are right; live with it.

At least it ain't another "WE DEMAND FIRMWARE" thread