Flange distance and back focus?

A question for you Mark,

Thought you had given up?

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,

They are not more precise One precise measurement can not be more precise than another measurement.

- how is it that these still need calibrating due to natural variations,

Several variations?

and yet the canon lenses magically are perfect and will apparently not require shimming or adjusting when used on a Canon made EF mount?

Wrong. Canon made the EF mount to fit their EF lenses while a PL mount is made by Arriflex who don't make lenses but made a lens mount to cover third party lens makers

Putting aside the fact that several people have mentioned that they have used the same lenses, and found they needed adjusting also

Care to name them? I counted a couple and besides those are not really a verifiable source on a forum like this with possible double named posters and those backing there favourite poster instead of the truth.

- how do you explain canon somehow being the exception?

Canon have reliably informed me their lenses are accurate and indeed invited me to send mine in for testing. Wish you would read my posts instead of trying to undermine me. Also Canon have reliably informed me their lens mounts are accurate and will work perfectly with their own camera mounts.
DP's like John will more often use the PL mount and more often than not have to shim lenses of all types and that is the nature of the professional world But this is not the case in the consumer world and although Canon CN-E lenses are professional They don't come with the same caveats more bespoke lenses might do. Canon made their lenses to fit their cameras and vice versa.
BM have said they originally made their EF mounts exactly the same spec for the EF lenses and changed it to fit those third party lenses like the Tokina.

For a long time now You Adam and John Brawley have tried to muddy the water But the truth is Canon are not lying or stretching the truth But there are some here who are and will seemingly go to great lengths not to make BM wrong over this.

Clearly BM want to make an EF Mount then they should have stuck to the EF spec in order to be professional.
If BM wanted to allow people wishing to make bespoke professional lenses fit and that may go out because of delicate internals then a PL mount version to the Arriflex spec and where lenses are made that allow shimming because their lenses are not exact. Don't forget the Arri PL mount is supposed to encompass all and lens manufacturers know this.
Different ball game with Canon.
If you want to more why don't you write to Canon and get more information instead of taking mickey mouse opinions on forums and using it as fact.

I need to stop giving you the benefit of the doubt Mark, I keep forgetting that it is not support or information which you seek, but validation.

I need to stop giving you the benefit of the doubt Mark, I keep forgetting that it is not support or information which you seek, but validation.

So much for the title forum guru.

So you believe the CN-E lenses and the Canon camera mounts are perfect and accurate? So why are they not in wide professional use? Why then do professional cinematographers all prefer the PL mount that has to be shimmed?

Yeah that makes total sense.

The EF mount is not a professional mount. No matter what Canon tell you.

Try your lenses on various Canon cameras and tell us how many had the witness marks spot on...

So you believe the CN-E lenses and the Canon camera mounts are perfect and accurate?

Yes.

So why are they not in wide professional use? Why then do professional cinematographers all prefer the PL mount that has to be shimmed?

That isn't true.
The EF mount was specifically designed for EF lenses. Using a Mount like PL designed for an arriflex camera by arri for third party lenses means the PL mount has become more popular.

The EF mount is not a professional mount. No matter what Canon tell you.

Of course its a professional mount That's why BM used it BM's mistake was they also wanted to cater for crappy lenses not adhering to the EF spec.

Try your lenses on various Canon cameras and tell us how many had the witness marks spot on

I don't need to have had it on good authority from Canon a multi million pound organisation as opposed to an agenda to back BM as unable to do no wrong by some members

Clearly you are a professional with a lot of experience using professional film cameras. So everything you say must be true.

I'll leave you to you deluded dream world because it's clear you are not interested in actually learning anything.

Oh and I have no agenda or need to back BM. I use many different tools for the work I do. I chose the right tool for the job and budget. I've also said on many occasions that the BM cameras have many issues. Issues I'm happy to work around when I need to.

Mark.

You actually don't know what you're talking about.

You have zero experience using cinema lenses and its rude to brush aside those that have and know better than you, especially when you started this thread and asked for help.

You're also using the diverting tactic of questioning my motives and those of others suggesting a blind allegiance to BM.

One could suggest the same could be said about your attitude to Canon.

I believe we've well and truly covered why you're in your situation. We've all posted ways you could independently verify what were positing. Were hardly "defending" blackmagic. Just stating how it is. No one is disputing fact aside from you.

Your knowledge is gleaned from reading forums like this one and reading and believing everything you're told rather than discovering for yourself first hand. Something that wouldn't be hard to do if you really cared about this.

Youre pissed because you were duped and you dont want to face you might have bought into the wrong lens / mount / camera.

Take some responsibility for your decisions. And stop posting as if you know the fix is as easy as four simple hex screws.

It just shows you have no idea...still...after many posts. You don't understand the nature of why you're expectations are so out of touch with everyone else.

JB

You actually don't know what you're talking about.

This is a generalisation If you cant be specific this is just plain arrogant.

You have zero experience using cinema lenses

I own my Professional Canon lenses I also own Zeiss superspeeds so how can I have ZERO experience?

and its rude to brush aside those that have and know better than you,

Its rude to ignore the fact BM don't have a proper EF specced mount and put all the onus on me as a customer.

especially when you started this thread and asked for help.

This was what I said in the OT
I just tested my Canon CN-E Primes and the lens witness marks do not match up and so the backfocus on my BM4K is out. How can I adjust back focus on the BM4K? Or can this be put right? One of the reasons I bought the CN-E lenses was so I could properly focus with a tape measure in a professional way with the BM4K.
Note I enquired WHY I got those reasons in the end from BM They alone have changed the dimensions of the EF spec screwing the witness marks on my EF professional lenses.

You're also using the diverting tactic of questioning my motives and those of others suggesting a blind allegiance to BM.

Speak to Canon about the tolerances We have a choice here We believe you or Canon who created the EF spec and assure me their tolerances are correct. Its BM tolerances that are out.

One could suggest the same could be said about your attitude to Canon.

You already did. I owe no allegiance to any manufacturer but by your own admittance friends with BM

I believe we've well and truly covered why you're in your situation. We've all posted ways you could independently verify what were positing. Were hardly "defending" blackmagic. Just stating how it is. No one is disputing fact aside from you.

Yes You've covered it and
Dismissed the fact Canon make professional primes with correct tolerances
Dismissed the fact BM have admitted they made their mount to a different size
Dismissed the fact Canon primes are not designed to be shimmed.
Dismissed the fact that consumers do not expect to go to a bespoke lens rental and pay wads of cash for shimming all their lenses to the specific needs of BM's camera

Your knowledge is gleaned from reading forums like this one and reading and believing everything you're told rather than discovering for yourself first hand. Something that wouldn't be hard to do if you really cared about this.

If that were the case I'd believe everything you said wouldn't I.
The truth is as a consumer I've got prime lenses that were built designed to work with an EF mount and an EF mount that is built wrongly. You expect me to go get my lenses not designed to be shimmed to be shimmed and blame Canon for lying Although you wouldn't say that in a straight way Just that Canon got it wrong and Im the one at fault as that hurts no one except as you wrongly think a Mr nobody that you can bully coherese and demean into stopping any just complaints about a wrongly specced mount

Youre pissed because you were duped and you dont want to face you might have bought into the wrong lens / mount / camera.

You're pissed because your determination to restructure reality is under threat.

Take some responsibility for your decisions. And stop posting as if you know the fix is as easy as four simple hex screws.

Yeah easy isn't it. Although even that would be difficult because BM individually set every sensor so every sensor measurement is going to be different ZERO standard mount. Its not EF as every camera will have a different measurement.

It just shows you have no idea...still...after many posts. You don't understand the nature of why you're expectations are so out of touch with everyone else.

Here you are speaking for your friends to step in and join you. That's how bullies operate John. Next thing you should do is get me banned for questioning the awful design of BM's implementation of the EF mount and complete BM's change with your help to the darkside.

You actually don't know what you're talking about.

This is a generalisation If you cant be specific this is just plain arrogant.

It would be obvious to anyone reading this thread because you conveniently ignore every single rebuttal of your "claims" whilst continuing to assert that Canon make lenses that don't need to be shimmed...because Canon told you they don't and they told you it can't be done....Meanwhile, you yourself later say that Canon said they could do it for you, I know of two lens techs that have done them and several others posted in kind.....it's just going round and round in circles now Mark....keep trying though...maybe it'll sink in eventually...

You have zero experience using cinema lenses

I own my Professional Canon lenses I also own Zeiss superspeeds so how can I have ZERO experience?

You have zero experience in the shimming and use of cinema lenses. How are those witness marks on your Superspeeds by the way ?

and its rude to brush aside those that have and know better than you,

Its rude to ignore the fact BM don't have a proper EF specced mount and put all the onus on me as a customer.

Well Mark, Canon don't either. None of their cameras are the right spec. You can't prove me wrong either cause you're too lazy to do so and take Canon at their marketing word.

especially when you started this thread and asked for help.

This was what I said in the OT
I just tested my Canon CN-E Primes and the lens witness marks do not match up and so the backfocus on my BM4K is out. How can I adjust back focus on the BM4K? Or can this be put right? One of the reasons I bought the CN-E lenses was so I could properly focus with a tape measure in a professional way with the BM4K.
Note I enquired WHY I got those reasons in the end from BM They alone have changed the dimensions of the EF spec screwing the witness marks on my EF professional lenses.

And we've truly covered the why. So far in two years your'e the only guy that's complained. No one is disputing that it's not the spec. The whole reason it's not the spec is because no lenses hit that spec.

You're also using the diverting tactic of questioning my motives and those of others suggesting a blind allegiance to BM.

Speak to Canon about the tolerances We have a choice here We believe you or Canon who created the EF spec and assure me their tolerances are correct. Its BM tolerances that are out.

My belief comes from my actual experience. Yours is based on what Canon tell you. Mine is actual experience shooting with Canon EF mount cameras and BM cameras as well as 5 years a camera prep technician where I actually measured, checked and shimmed lenses daily. My experience has also been backed up by every other poster in this thread. You can believe me or you can believe what Canon tell you I guess.

One could suggest the same could be said about your attitude to Canon.

You already did. I owe no allegiance to any manufacturer but by your own admittance friends with BM

Mark. You questioned my views and those of others and accused us of blind faith. So far, I've been dealing with the question and haven't refuted that BM's EF mount isn't suitable for using your lenses. How is that blindly supporting BM ? Meanwhile, you get to call us into question because it's not going your way ?

I'm a working cinematographer. I'm camera agnostic. I use them all cause they are just tools and I choose the right one for the job where the resources allow me. Right now I'm using F55's cause I like the DR and the global shutter. Last job was Alexa. Job before that was Alexa, EPIC, Canon C300 and BM. I don't get paid by BM or anybody else for my opinion. It is my opinion and I give it freely and as I said, I was initially sympathetic to you. Now I just think you deserve the trouble you have.

I believe we've well and truly covered why you're in your situation. We've all posted ways you could independently verify what were positing. Were hardly "defending" blackmagic. Just stating how it is. No one is disputing fact aside from you.

Yes You've covered it and
Dismissed the fact Canon make professional primes with correct tolerances

Yes because it doesn't matter because all cameras and cinema lenses need fine tuning and shimming and should be checked for every job...so yeah I dismiss that.

Dismissed the fact BM have admitted they made their mount to a different size

No I haven't. I even explained why...you couldn't care less though and ignored the logic that everyone else agrees with as to why they did that. You also totally ignored me correcting your constant referral to them changing it due to matching the Tokinas when it was also regular canon made EF lenses you hypocrite. I had to go and friggin post you the links to threads just to "prove" it to you.

Dismissed the fact Canon primes are not designed to be shimmed.

Actually I told you how I spoke to two lens technicians who both told me that they had done it and then pointed out the contradicting information from Canon themselves who said that it couldn't be done, but you could send it in to them to be done...

Dismissed the fact that consumers do not expect to go to a bespoke lens rental and pay wads of cash for shimming all their lenses to the specific needs of BM's camera

Well it's a fact. I didn't dismiss it. It's a truth Mark. I guess it hurts you but thats normal practice. Or can buy a lens that allows you to shim yourself if you don't want to do what is in fact accepted normal practice.

Your knowledge is gleaned from reading forums like this one and reading and believing everything you're told rather than discovering for yourself first hand. Something that wouldn't be hard to do if you really cared about this.

If that were the case I'd believe everything you said wouldn't I.
The truth is as a consumer I've got prime lenses that were built designed to work with an EF mount and an EF mount that is built wrongly.

No. This is the truth which you are not accepting.

You have lenses that are EF mounted and to have them accurately line up to their witness marks they should be checked, and if necessary, re-shimmed to be accurate with that specific camera you're using, be it a C500, C100, BM4K, 5DMK2. They will all be different. You need to have them shimmed for each camera because EF mount's can't be shimmed and you can only make them accurate if you do the lenses.

You expect me to go get my lenses not designed to be shimmed to be shimmed and blame Canon for lying Although you wouldn't say that in a straight way Just that Canon got it wrong and Im the one at fault as that hurts no one except as you wrongly think a Mr nobody that you can bully coherese and demean into stopping any just complaints about a wrongly specced mount

What are you talking about. I'm not bullying you. You're the one that constantly conveniently ignores blatant evidence that contradicts your opinion, or a second hand information from Canon as fact. We've even suggested how you could verify this for yourself, but you choose not to. It's hard to be sympathetic to anyone that won't help themselves to understand. I'm happy to go on record and say Canon are LYING about their lenses not need to be shimmed. They don't have it wrong. It's just the situation Mark. This is normal practice and you think lenses are made perfect and stay perfect and that canon EF mounts are perfect somehow and would stay perfect as well. Well they aren't and that's why it's normal to be talking about re-shimming lenses.

Youre pissed because you were duped and you dont want to face you might have bought into the wrong lens / mount / camera.

You're pissed because your determination to restructure reality is under threat.

Actually I'm pissed because you're so ignorant as to believe everything you read and then post it as fact. Go and test the lenses on other Canon cameras Mark.

Take some responsibility for your decisions. And stop posting as if you know the fix is as easy as four simple hex screws.

Yeah easy isn't it. Although even that would be difficult because BM individually set every sensor so every sensor measurement is going to be different ZERO standard mount. Its not EF as every camera will have a different measurement.

Yeah Mark every lens is different. Every single flange depth is different too. They are all not quite the same. tolerances in this case mean that witness marks don't hit infinity.

It just shows you have no idea...still...after many posts. You don't understand the nature of why you're expectations are so out of touch with everyone else.

Here you are speaking for your friends to step in and join you. That's how bullies operate John. Next thing you should do is get me banned for questioning the awful design of BM's implementation of the EF mount and complete BM's change with your help to the darkside.

[/quote]

I don't even know what you're talking about Mark. Who are my friends ? If you have a problem with me you can report me to moderators. They have pretty specific guidelines on behaviours that are acceptable. I don't believe I am bullying you. You're the one that likes to make personal attacks and question my personal motives and that of others. Don't be a sook.

It does sound like you're crying for the teacher when it's not going your way, and yet as far as I can see, all I've done is tell you how to easily solve your problem and why it is a problem that exists in the first place, and why it doesn't have to be that big of a deal.

Knock yourself out fella. I can keep doing this till the cows come home, because I have the weight of knowledge that you can't be bothered verifying for yourself.

jb

Mark, I am all for critizing BMD where there is something to critize.
But you are just trying to talk reality into distortion.

If you don't believe John, maybe you will believe David Samuelson's 'Hands-on Manual for Cinematographers'?

Quote from p. 62 chapter 5.3 Flange Focal Depth Settings:
The distance from the face of lens mount to the back of the aperture plate must be accurately set to within a tolerance of 0.0025 mm in normal room temperature. This can only be done by replacing the film with a flat plate and using a highly accurate depth gage to measure the distance.
…
It is equally important to check that the lens flanges are set to the nominal distance with same degree of accuracy. To achieve this, manufacturers make the final adjustment to each lens, individually, on an MTF bench. Only by keeping a very tight control of both the camera and the lens flange settings is it possible to achieve complete interchangeability between all lenses on all cameras.

It would be obvious to anyone reading this thread because you conveniently ignore every single rebuttal of your "claims" whilst continuing to assert that Canon make lenses that don't need to be shimmed...because Canon told you they don't and they told you it can't be done....Meanwhile, you yourself later say that Canon said they could do it for you, I know of two lens techs that have done them and several others posted in kind.....it's just going round and round in circles now Mark....keep trying though...maybe it'll sink in eventually...

But not the CN'E primes Right John? You like doing that don't you holding back information for later Knowing the CN-E zoomis designed to be shimmed. So your techs have shimmed a CN-E prime lens for use on a canon camera? Or is that for use on a BM camera? Statements are just so loaded and not the spirit of truth or fairplay.

You have zero experience in the shimming and use of cinema lenses. How are those witness marks on your Superspeeds by the way ?

Now your just ignoring a fact and adding an untruth. Shimming a lens is no big deal if youre using a PL mount which was designed for shimming.
Another spiked question? Actually my superspeeds are accurate all the way from the 60's using an Arri bayonet mount on an Arri real film camera.

and its rude to brush aside those that have and know better than you,

Its rude to ignore the fact BM don't have a proper EF specced mount and put all the onus on me as a customer.

Well Mark, Canon don't either. None of their cameras are the right spec. You can't prove me wrong either cause you're too lazy to do so and take Canon at their marketing word.

If you were right then where are all the forums with those that bought the 1dc screaming about where to get their lenses shimmed? Or the C500 or C300 users? As I thought Nowhere.

And we've truly covered the why. So far in two years your'e the only guy that's complained. No one is disputing that it's not the spec. The whole reason it's not the spec is because no lenses hit that spec.

Good so its BM's fault for not having the correct EF spec?

My belief comes from my actual experience. Yours is based on what Canon tell you. Mine is actual experience shooting with Canon EF mount cameras and BM cameras as well as 5 years a camera prep technician where I actually measured, checked and shimmed lenses daily. My experience has also been backed up by every other poster in this thread. You can believe me or you can believe what Canon tell you I guess.

Did you actually shim Canon lenses? Which ones?

Mark. You questioned my views and those of others and accused us of blind faith. So far, I've been dealing with the question and haven't refuted that BM's EF mount isn't suitable for using your lenses. How is that blindly supporting BM ? Meanwhile, you get to call us into question because it's not going your way ?[/quote
Good so we both agree BM's EF mount is not suitable for professional EF lenses. Where we don't seem to agree is that Canon make EF mounts and lenses that are accurate or that can be accurate In other words apologising for BM's error and blaming it on Canon.

I'm a working cinematographer. I'm camera agnostic. I use them all cause they are just tools and I choose the right one for the job where the resources allow me. Right now I'm using F55's cause I like the DR and the global shutter. Last job was Alexa. Job before that was Alexa, EPIC, Canon C300 and BM. I don't get paid by BM or anybody else for my opinion. It is my opinion and I give it freely and as I said, I was initially sympathetic to you. Now I just think you deserve the trouble you have.

You're the one telling us Canon make EF mounts that are out on their pro cameras and lenses. I think its your opinion that is in trouble Not mine. You feign sympathy will dishing out misdirection You hold out the professional card while using carefully chosen words that cover yourself.

As I said John Bullying and misdirection. Good at that aren't you.

Yes because it doesn't matter because all cameras and cinema lenses need fine tuning and shimming and should be checked for every job...so yeah I dismiss that.

Even those using the EF spec not designed for shimming.

No I haven't. I even explained why...you couldn't care less though and ignored the logic that everyone else agrees with as to why they did that. You also totally ignored me correcting your constant referral to them changing it due to matching the Tokinas when it was also regular canon made EF lenses you hypocrite. I had to go and friggin post you the links to threads just to "prove" it to you.

More aggression when the argument isn't going your way? Or is it going your way and you stick the boot in anyway? Should I be scared of you? Is that what you want.

Actually I told you how I spoke to two lens technicians who both told me that they had done it and then pointed out the contradicting information from Canon themselves who said that it couldn't be done, but you could send it in to them to be done...

I never said that What I said was Canon would check my lenses. Nothing else.

Well it's a fact. I didn't dismiss it. It's a truth Mark. I guess it hurts you but thats normal practice. Or can buy a lens that allows you to shim yourself if you don't want to do what is in fact accepted normal practice.

Not according to Canon. Certainly there are very few places that do this as I cant find one so I hardly think its normal for these lenses.

You have lenses that are EF mounted and to have them accurately line up to their witness marks they should be checked, and if necessary, re-shimmed to be accurate with that specific camera you're using, be it a C500, C100, BM4K, 5DMK2. They will all be different. You need to have them shimmed for each camera because EF mount's can't be shimmed and you can only make them accurate if you do the lenses.

Not according to Canon and this hardly seems likely does it?

What are you talking about. I'm not bullying you.

Actually I pissed because you're so ignorant as to believe everything you read and then post it as fact.

Take some responsibility for your decisions. And stop posting as if you know the fix is as easy as four simple hex screws.

It just shows you have no idea...still...after many posts. You don't understand the nature of why you're expectations are so out of touch with everyone else.

I don't even know what you're talking about Mark. Who are my friends ?

Don't be a sook.

It does sound like you're crying for the teacher when it's not going your way,

Knock yourself out fella. I can keep doing this till the cows come home,

because I have the weight of knowledge that you can't be bothered verifying for yourself.

You obviously believe you know everything. Canon don't agree.

Mark, I am all for critizing BMD where there is something to critize.
But you are just trying to talk reality into distortion.

Not at all Canon EF lenses are built to certain tolerances to match their cameras. That's a fact not being recognised here. My EF lenses would work fine on any professional Canon camera.

Quote from p. 62 chapter 5.3 Flange Focal Depth Settings:
The distance from the face of lens mount to the back of the aperture plate must be accurately set to within a tolerance of 0.0025 mm in normal room temperature. This can only be done by replacing the film with a flat plate and using a highly accurate depth gage to measure the distance.
It is equally important to check that the lens flanges are set to the nominal distance with same degree of accuracy. To achieve this, manufacturers make the final adjustment to each lens, individually, on an MTF bench. Only by keeping a very tight control of both the camera and the lens flange settings is it possible to achieve complete interchangeability between all lenses on all cameras.

So you're saying Canon's quality control is very high? Is there a point here?

Mark, so did you perform an accuracy test with your lens on a Canon camera, yes or no?

But not the CN'E primes Right John?

Yeah Mark. CN-E primes. And yeah I know the zooms are "easier" to do. Seems you know more than you let on hey ?

Another spiked question? Actually my superspeeds are accurate all the way from the 60's using an Arri bayonet mount on an Arri real film camera.

I bet they aren't.

If you were right then where are all the forums with those that bought the 1dc screaming about where to get their lenses shimmed? Or the C500 or C300 users? As I thought Nowhere.

In your own words you want me to do your research ?

Plenty of people on this forum have already said otherwise. You look and you'll find the other evidence. You don't want to though do you.

Good so its BM's fault for not having the correct EF spec?

Oh you so want it to be BM's fault don't you but I'd argue it's Canon's fault for creating a spec they don't adhere to themselves. BM are simply doing what the VERY VAST majority of their customers want.

Did you actually shim Canon lenses? Which ones?

I don't do CN-E primes mark cause they've only been out int he last couple of years. I did plenty of Canon / Century FD adapted lenses though like the 300mm 2.8, 200mm 1.8, the 150-600 zoom, the 16-35 F2.8 zoom.

Good so we both agree BM's EF mount is not suitable for professional EF lenses.

Yes. I wouldn't use cinema lenses with EF mount, but plenty of people do and choose to. Whom am I to say what people should use.

Where we don't seem to agree is that Canon make EF mounts and lenses that are accurate or that can be accurate In other words apologising for BM's error and blaming it on Canon.

Well yeah because Canon don't adhere to their own spec Mark.

You're the one telling us Canon make EF mounts that are out on their pro cameras and lenses. I think its your opinion that is in trouble Not mine. You feign sympathy will dishing out misdirection You hold out the professional card while using carefully chosen words that cover yourself.

Sorry, why haven't you actually tested any of your lenses on an E mount body again ?

As I said John Bullying and misdirection. Good at that aren't you.

Report me.

Even those using the EF spec not designed for shimming.

If they are CN-E lenses they can be shimmed. Any lens can be really, but no regular EF mount will have accurate witness marks anyway irrespective of the shim so no one bothers.

More aggression when the argument isn't going your way? Or is it going your way and you stick the boot in anyway? Should I be scared of you? Is that what you want.

And yet you conveniently ignore what I point out.... That you pretended not to hear me tell you it wasn't because of the Tokina's that BM changed the EF mount tolerance and kept repeating an untruth.

I never said that What I said was Canon would check my lenses. Nothing else.

You reported in your second post from Canon that they could change it for you to a different spec that wouldn't be "right" and you'd have to adjust it again. So Canon told you they could adjust it but you'd have to adjust it again....
viewtopic.php?f=2&t=22052&start=50#p138368

Not according to Canon. Certainly there are very few places that do this as I cant find one so I hardly think its normal for these lenses.

Yeah Mark. It is.

Not according to Canon and this hardly seems likely does it?

Yeah Mark. Still is. Saying Canon don't say so doesn't make it true. It is.

You obviously believe you know everything. Canon don't agree.

I don't know everything. I hope I never do. But If I wanted to learn something I'd go and find out for myself if I needed to know. Why don't you take a chance and do just that.

JB

So you've never shimmed CN-E primes and yet here you are telling me its innaccurate.

Do you see the fatal flaw in your argument?

Mark, is that kind of a therapy session for you?
Otherwise I do not see any sense in arguing in circles here.
What exactly do you want from the people in this forum here? An excuse for the problem you are facing now? Money? Friends in tears?

Please help us to understand your agenda.

Mark, is that kind of a therapy session for you?
Otherwise I do not see any sense in arguing in circles here.
What exactly do you want from the people in this forum here? An excuse for the problem you are facing now? Money? Friends in tears?

Please help us to understand your agenda.

I want acknowledgement I bought a BM camera purporting to have an EF lens and that EF lens is not built to the EF spec and that is the reason my lenses don't work and not because I stupidly didn't realise all Canon lenses need shimming.
I want acknowledgement that my CN-E lenses are accurate within obvious tolerances and will work properly on Canons professional lineup like the 1DC C500 and the C300 and an end to the silliness being touted here.

What was your agenda in that last post? Clearly you think they are right that Canon lenses all need shimming. Why not give your reasons for this instead of underming me.

I want acknowledgement I bought a BM camera purporting to have an EF lens and that EF lens is not built to the EF spec and that is the reason my lenses don't work and not because I stupidly didn't realise all Canon lenses need shimming.
I want acknowledgement that my CN-E lenses are accurate within obvious tolerances and will work properly on Canons professional lineup like the 1DC C500 and the C300 and an end to the silliness being touted here.

Why? to what end?

Quote from p. 62 chapter 5.3 Flange Focal Depth Settings:
The distance from the face of lens mount to the back of the aperture plate must be accurately set to within a tolerance of 0.0025 mm in normal room temperature. This can only be done by replacing the film with a flat plate and using a highly accurate depth gage to measure the distance.
…


Hi Robert,

As you describe it is easy to measure the flange depth of a film camera to a high degree of accuracy. Although I have the equipment to do so I would not try the same technique on a video camera.

Firstly there is usually an IR cut filter in front of the sensor and often a prism block also.

Secondly even if the sensor is accessible it would almost certainly be damaged by the measuring instrument.

I guess that the manufacturers would use an accurately calibrated lens to check the flange distance and observe the result on a good monitor. Alternatively it is possible to examine the image on the sensor by using an auto-collimator.

I have recently had reason to doubt the flange distance on my BMPCC. The only information I could get from BMD is that they build some ‘give’ into the flange distance. As expected the ‘give’ means the flange distance is a little short which is much preferable to being a little long. However BMD are a little coy about putting a figure on the magnitude of their ‘give’. As described in other threads in this forum I have sorted out my problems and in the process I have decided that the flange distance on my BMPCC is slightly long rather than short.

What is puzzling me about this incredibly long thread is why anyone would want to set focus with a tape measure. When I last used my 300 mm lens there was a pond 5 feet deep between camera and subject. That was a bad start for a tape measure user. At a distance of about 30 feet it was hard to even see how much lens barrel rotation there was between being in focus and being out of focus. To use a graduated scale on this lens reliably at this range you would need more than the occasional witness mark, you would need a vernier scale at least and a reference table. In my school days I used to take still photographs (film) of birds at their nests. The witness marks on my lens were way out, so with the help of a piece of ground glass and a tape measure I made a ‘correction’ list. So using my revised table I would set focus by the scale and sit back and wait for my subject. It worked but not as well as a field monitor with a colour focus assist.

I want acknowledgement I bought a BM camera purporting to have an EF lens and that EF lens is not built to the EF spec and that is the reason my lenses don't work and not because I stupidly didn't realise all Canon lenses need shimming.

No, it's the latter.

I want acknowledgement that my CN-E lenses are accurate within obvious tolerances and will work properly on Canons professional lineup like the 1DC C500 and the C300 and an end to the silliness being touted here.

Rent those cameras and test them.

I want acknowledgement I bought a BM camera purporting to have an EF lens and that EF lens is not built to the EF spec and that is the reason my lenses don't work and not because I stupidly didn't realise all Canon lenses need shimming.

No, it's the latter.

I want acknowledgement that my CN-E lenses are accurate within obvious tolerances and will work properly on Canons professional lineup like the 1DC C500 and the C300 and an end to the silliness being touted here.

Rent those cameras and test them.

Why don't you present your evidence that professional Canon lenses and cameras are all out?

Why don't you present your evidence that professional Canon lenses and cameras are all out?

Why don't you present your evidence to the contrary?

an email from a sales/support rep is not evidence -it is hearsay.

Why don't you present your evidence that professional Canon lenses and cameras are all out?

Why don't you explain how that counters anything I said.

So, I got my URSA and a CNE 30-105mm zoom. Imagine my surprise when the lens did not act as a parfocal lens should. I took the URSA and lens to be checked out at Abel Cine in New York City (where I purchased the gear). The lens backfocus was perfect on the collimator. When the camera was tested, its mount threw the backfocus totally off. The Abel Cine lens tech called BM and was told no backfocus adjustment was built for the URSA EF-mount. Fortunately, the lens tech was able to modify (with BM's blessing) some Zeiss shims and brought the mount to true. It took over a hundred microns-worth of shimming. Now, all is happy.

So, I got my URSA and a CNE 30-105mm zoom. Imagine my surprise when the lens did not act as a parfocal lens should. I took the URSA and lens to be checked out at Abel Cine in New York City (where I purchased the gear). The lens backfocus was perfect on the collimator. When the camera was tested, its mount threw the backfocus totally off. The Abel Cine lens tech called BM and was told no backfocus adjustment was built for the URSA EF-mount. Fortunately, the lens tech was able to modify (with BM's blessing) some Zeiss shims and brought the mount to true. It took over a hundred microns-worth of shimming. Now, all is happy.

And to be clear...

It's not just URSA, no canon EF mount camera can be "re-shimmed" either unless it's the C500 or something like the EF mount on a RED (by moving the sensor).

EF mount really isn't the best mount to go for if you want this kind of performance from a lens.

JB

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.

Ain't that the truth!

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.

Best thing I have ever quoted, I think I'll use this (steal it) some day

Well, that's a heck of a lot of reading,...

Devils advocate question,..

Why the almost exclusive reliance on the Witness Marks?

Does the OP not check the focus with an EVF or external monitor or use the Expanded Focus view?


I don't know about everyone else, but when choosing which lenses to use out of my kit for a specific gig I decide based on the look I want to achieve, and the consistency of achieving that look across the whole production, and certainly not on whether the focus marks on the barrel are spot on or not.

If the witness marks on a prime are out, who really cares, as once the DoP or 1AC has gone through and set their focus marks on the follow focus unit, repeatable focus pulls can be achieved.
The barrel markings should only ever be a guide, not a rigid measure,... after all, what percentage of performers accurately and repeatedly hit their marks 100% of the time?
( The answer to that is 'none', as actors will aim to hit the marks, but their job is to provide a performance first and foremost. )

Sure, shimming will get perfect witness marks, but on a 'cine' lens (ie, one with no iris clicks or clutched focus rings,.. or pretty housings that keep your focus rig and matte box in the same spot on the rails) you're still going to get beautiful imagery out of a good camera and lens if the marks stenciled on the barrel are off.

Shimming has also been an industry standard practice during the entire history of B4 mount ENG and Production cameras, but for them it's more important for a close fitting finish so there are no light leaks, as those lenses have a built in back-focus adjustment, allowing them to maintain their Parfocal operation - something one doesn't have to be so concerned with when using a Prime lens.

Maybe my cynicism to the issue is just from being spoiled by using classic manual K-mount lenses - the only time I've had to worry about the witness marks being 'out' was when using SMC-A lenses on a cheap K to M4/3 adapter on a BMPC, where the flange to flange distance was about 0.9mm too short, and shimming made it so my parfocal zooms would function properly.

So in my mind it boils down like this.
Are they good lenses? Does the image they focus on the sensor look how you desire it to be? Does the camera record those images at a high enough standard to meet the production requirements? Can you focus the image to an adequately high enough standard?
If so, then the barrel markings matching the measurement of a tape is not the biggest concern of any day on set.

Besides, did anyone check to make sure the tape measure hadn't been stretched, or was even accurate to begin with?

If the witness marks on a prime are out, who really cares, as once the DoP or 1AC has gone through and set their focus marks on the follow focus unit, repeatable focus pulls can be achieved.
The barrel markings should only ever be a guide, not a rigid measure,... after all, what percentage of performers accurately and repeatedly hit their marks 100% of the time?
( The answer to that is 'none', as actors will aim to hit the marks, but their job is to provide a performance first and foremost. )

It's true, they won't hit their marks 100% of the time, because no one's perfect. If you set your marks and focus points correctly though, you can get them within the depth of field a large percentage of the time, and for some shots it really does matter, assuming that you're taking your compositions and blocking seriously as storytelling tools.

For my first few attempts at making films that were more than living portraits (I started out as a photographer, so my first films were really a set of Harry Potter style still photos, if you know what I mean -- pretty, but hardly cinematic), I did use a tape measure for focus marks. When we used PL mount lenses on Arri and Aaton super 16 camera, it made focus pulls pretty easy.

With the BMCCs though, we're using lenses that have decent but not precise witness marks, and since they're on MFT they are of course not properly shimmed... mostly. I think the SLR Magic lens has pretty good witness marks, but since mine happens to be super wide and it's the only one, we largely rely on focus peaking to get focus. It works out to be mostly the same amount of time, but still requires precise blocking for shots using long lenses with important focus pulls, especially getting the timing right.

But you know what? Most of our experienced actors, that is the ones who have film experience, hit their marks spot on most of the time. The ones that miss them regularly stand out like sore thumbs as a result, and that's when we realize that the rest are nailing them. The theater actors just don't realize until their on set and missing marks that ruin the shot how important it is to hit their marks and still deliver the same performance, but once they understand why, it becomes just a matter of giving them some positive reinforcement, and taking a few extra tries so that they can feel the right spot.

We're making do with old SLR lenses and a still photography camera mount for budget reasons though. Not preference. Once you've used professional cinema gear, the photograph stuff all feels a bit hacky by comparison. Hence my decision to pre-order an Ursa Mini with a PL mount...

My reason for shimming the sensor was so the lens acted as a parfocal lens should. Interestingly, when using the Tokina 11-16 with the newly shimmed sensor, it too, acted as a parfocal. BTW the cost to shim the sensor was less than $200.

Well, that's a heck of a lot of reading,...

Devils advocate question,..

Why the almost exclusive reliance on the Witness Marks?

Does the OP not check the focus with an EVF or external monitor or use the Expanded Focus view?


I don't know about everyone else, but when choosing which lenses to use out of my kit for a specific gig I decide based on the look I want to achieve, and the consistency of achieving that look across the whole production, and certainly not on whether the focus marks on the barrel are spot on or not.

If the witness marks on a prime are out, who really cares, as once the DoP or 1AC has gone through and set their focus marks on the follow focus unit, repeatable focus pulls can be achieved.
The barrel markings should only ever be a guide, not a rigid measure,... after all, what percentage of performers accurately and repeatedly hit their marks 100% of the time?
( The answer to that is 'none', as actors will aim to hit the marks, but their job is to provide a performance first and foremost. )

Sure, shimming will get perfect witness marks, but on a 'cine' lens (ie, one with no iris clicks or clutched focus rings,.. or pretty housings that keep your focus rig and matte box in the same spot on the rails) you're still going to get beautiful imagery out of a good camera and lens if the marks stenciled on the barrel are off.

Shimming has also been an industry standard practice during the entire history of B4 mount ENG and Production cameras, but for them it's more important for a close fitting finish so there are no light leaks, as those lenses have a built in back-focus adjustment, allowing them to maintain their Parfocal operation - something one doesn't have to be so concerned with when using a Prime lens.

Maybe my cynicism to the issue is just from being spoiled by using classic manual K-mount lenses - the only time I've had to worry about the witness marks being 'out' was when using SMC-A lenses on a cheap K to M4/3 adapter on a BMPC, where the flange to flange distance was about 0.9mm too short, and shimming made it so my parfocal zooms would function properly.

So in my mind it boils down like this.
Are they good lenses? Does the image they focus on the sensor look how you desire it to be? Does the camera record those images at a high enough standard to meet the production requirements? Can you focus the image to an adequately high enough standard?
If so, then the barrel markings matching the measurement of a tape is not the biggest concern of any day on set.

Besides, did anyone check to make sure the tape measure hadn't been stretched, or was even accurate to begin with?

It's all about personal preference, this is why I argue that in 2015 there are better engineering solutions than building a $20K+ lens to impossible tolerances.

BM cameras do not haven't "back focus" adjustment. canon E F mount is not shimable. You may need to contact BM about redoing the lens mount back to 44mm, but even then, doubt the witness marks are going to be accurate. The only lenses I know of with repeatable, accurate witness ,arks. Are PL mount Cine glass, since the PL,mount is shimable to adjust back focus.

The OP no longer needs advice, if he ever did. This thread is over a year old...

Thanks John for your patience to explain this, really informative.... Mark , you need to respect the professional viewpoints put forward and stop being persistent with yours... This forum is really great and lets maintain the dignity of this forum.

Thanks John for your patience to explain this, really informative.... Mark , you need to respect the professional viewpoints put forward and stop being persistent with yours... This forum is really great and lets maintain the dignity of this forum.

It's an old thread that someone else posted to recently. Your comment doesn't seem fair to Mark at this time as he's understanding of the advice he's received and hasn't made further comment in this thread. It is certainly fair to recommend the URSA/Mini cameras go back to the 44mm EF mount FFD, which Mark respectfully suggested in the URSA Mini 4.6K thread; but of course, I think those requests may be ignored.

Rick Lang
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Thanks Rick. Yes it would be nice if BM listened and implemented a solution to their EF mount as I would so like to buy the Mini for my EF lenses!
I guess though if I am one of a small number of people wanting this it wont get done!

Thanks John for your patience to explain this, really informative.... Mark , you need to respect the professional viewpoints put forward and stop being persistent with yours... This forum is really great and lets maintain the dignity of this forum.

It's an old thread that someone else posted to recently. Your comment doesn't seem fair to Mark at this time as he's understanding of the advice he's received and hasn't made further comment in this thread. It is certainly fair to recommend the URSA/Mini cameras go back to the 44mm EF mount FFD, which Mark respectfully suggested in the URSA Mini 4.6K thread; but of course, I think those requests may be ignored.

Rick Lang
Sent using Tapatalk HD

Thank you Rick. I would just like to add one thing to this post.

Arri, which has always used third party lenses for their cameras as pointed out by PL mounted people here, have added EF mounts to their Arri Amira. Red also has two mounts to their cameras, PL and EF.

So, its not entirely true that EF mount is not for professional people. Some people might believe this, but Arri and Red, who make cameras for professionals do not seem to agree with PL mounted professionals.

Now, Canon CN-E EF mount lenses work perfectly with Arri Amira and Red. They should work fine with BMD EF mounts too. Or else, BMD cameras are faulty.

Edit: Here, I would also like to add that BMD cameras should have EF lock mounts too as is available with other cameras.

My guess is Arri did the EF version for the rental market that doesn't has/wants to pay for, PL glass. I can't imagine anyone would actually buy an Arri camera in anything other than PL mount.

Although, I do wish that BMD would put out a more robust EF mount like on the C500/300mkII/Red. Also, I still can't believe we don't have lenses that have digital, adjustable witness marks.

I can't imagine anyone would actually buy an Arri camera in anything other than PL mount.

I would have thought so too. But five years ago.

... Now, Canon CN-E EF mount lenses work perfectly with Arri Amira and Red. They should work fine with BMD EF mounts too. Or else, BMD cameras are faulty.

Subrata, no argument from me but I do respect there's a lot of people who are probably hoping the URSA/Mini EF FFD is just short of 44mm.

Edit: Here, I would also like to add that BMD cameras should have EF lock mounts too as is available with other cameras.

Amen, even if it increased the cost to match the cost for the PL mount URSA/Mini cameras.

Rick Lang
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