16x Manual lens breathes-Waah!
 

I was shooting with the Canon 16x manual lens on my XL2 and everything was great.

That is, until I had to rack focus for a scene and the lens breathed in a really bad way. I had to stop and put on the 20x auto lens which, to my surprise, did not breathe. I used the 20x on the rest of the production.

Has anyone had a problem with their 16x manual lens breathing? It makes the shot look like I'm zooming while I rack. I have used older cine lenses on film cameras that have breathed a little, but this was ridiculous.

I am currently waiting for my own Cine Tech Follow focus rig, but it was a real pain in the butt to have to pull focus on the 20x auto lens with no FF gear. I'm seriously thinking of getting rid of the 16x. Luckily Cine Tech now makes a gear for the 20x, but I really like the 16x because it's geared and doesn't do that whole infinite focus ring thing.

I'm curious to hear if other folks have the same problem. I called ZGC (who are great), where I got my whole package from and they said it's a flaw of the lens.

I'd really like to give Canon a piece of my mind. This is unacceptable. Do their other broadcast lenses breathe? Alas, I fear that because this is a prosumer lens they don't care.

Who do I contact at Canon?

I've never heard that term before, what do you mean when a camera "breathes"?

Also, where are you purchasing your Cinetech follow focus from? Do you have their matte box as well?

Breathing occurs when the focus point of a lens is changed and the angle of view changes slightly by either widening out or zooming in. It appears as if the frame is breathing. This flaw is not desirable. There shouldn't be any movement noticable other than the shift in focus. The picture should not seem to zoom in, or out, when racking.

Say I have a two shot and the camera is locked down. One person is five feet away and the other person is ten feet away. When I rack focus from one to the other, the lens seeming to slightly zoom in or out as I rack back and forth between the two people is very distracting.

I have the Chrosziel Matte box, but I'm still waiting for the bracket and rods. I was going to get either the Cine Tech Mini Follow Focus, or the Universal. Now, I'm contemplating getting the Studio FF but that's $2500. Oy!

What he means is that the focal length changes as you vary the focus distance and yes, my 16x does it and it isn't subtle either! It's much more noticeable at short focal length where the depth of field is greatest because things tend to stay sharper irrespective of where the focus ring is set and you can really see the zoom. Interesting!

Does this happen with the 14X Manual as well? I'm contemplating getting one of these lenses and up until now was planning on going with the 16X...

I've used the full manual 16x extensively on the XL1s, and I've had the same problem. Never knew there was a term for it before, and it was really only noticeable when I was shooting for a high DOF.

If the backfocus were set incorrectly would that amplify this problem? If so, that may have been the case for me.

Lens breathing is always more of an issue with zooms than prime (fixed focal length lenses), and is a function of the number of lens elements and sophistication of the lens. For the relatively low price of these lenses, a certain amount of breathing is expected. You will see it on the 14x manual as well as the 16x. The best way to hide breathing is to make a small move (pan or tilt) during the rack. Some may find the degree of breathing present with these lenses to be objectionable, others may not be concerned.

Yeah, I've been compensating with small moves, but to alleviate the problem I've been using the 20x lens. I'm waiting for the FF gears to come from Cine Tech.

I don't mind the 20x it's a nice lens, but it looks really goofy, like a giant marshmallow. It's the infinite focus that bugs me. I believe the Cine Tech has a lockout for that .

I'm just really disappointed that it breathes.

I'm going to go bite my pillow now.

You might want to find one of the older generation 14x manual lenses and test this. I can rack between the 2 objects with great precision and there is no measureable "swelling" or breathing of the frame. Perhaps this is because the 14x has a manual ring to control not only the zoom but also the iris. Even so, it is a cheap lens at only 900 bucks...

That shouldn't be a factor, it's the design of the lens itself that causes the image to breathe.

I will certainly consider an older lens. Silly me for thinking the newer lens would be better.

I've seen this "effect" but never knew the proper term for it. Thanks Michael,

In my freshman (and only) year at NYU's film school, I found myself camera assisting on a bunch of senior and grad student films with the Arri 16BL. This camera used the Angeniuex 12-120 zoom in a big blimp housing (this lens has been discussed in this forum as an inexpensive way to mate PL film optics with a mechanical adaptor to the XL1). This is a notoriously "breathy" lens--you really notice the magnification effect when spinning the focus substantially.

On one film, I had to rack from close focus to infinity. No follow focus was available for that camera, and the blimp housing made rack focusing difficult--you had to literally use two hands to rotate the barrel! When the footage came back, the director accused me of hitting the zoom lever when I was focusing. I suggested that since it had the same effect every time and for the same amount, perhaps something else was causing this. None of us were apparently aware of the phenomenon of lens breathing...I guess we all learned eventually!

Yep, those old Angenieux 12-120 lenses breathed more than a dirty old man at a porn flick. All zoom lenses do, some more than others. Primes will too but the better the lens, the less it breathes. Usually it's not too horrible with a good zoom lens except under certain circumstances, like when you are focused down to 3-4 feet and then shift focus to 30-40 feet. You can experiment with different focal lengths--for example, try moving the camera farther back from the foreground subject, so that instead of being, say 4 feet from it, you are 10 feet, but zoom in tighter to the area you want. The lens I use on a DSR500 (my 15 year old Nikkor ED 8.5-127mm) really breathes when I'm focused down to that closest range. If I can get back to beyond 10 feet or so, it's not nearly so noticeable.

Well I see breathing in pro production films all the time - I just assumed that it was just one of those things.

Also Mark, assuming you use the 20x, aren't you still going to lose the ability to reproduce focus pulls due to the nature of the lens? How is that Cine Tech thing going to solve anything other than giving you a different way to turn the barrel?

Aaron

Karl puts a focus gear right over the rubber focus ring. Like the DVX, it's not quite the infinite spinning of the focus ring but it's close. I forget, the 20x is about 100° rotation of the focus ring, from closest focus to ∞. Don't quote me.

I'm still waiting to actually get my CineTech and I'm chomping at the bit to shoot more. 'Course I'd be REALLY psyched to shoot some 35mm FILM.

If you go to the Cine Tech website there's a pic of it right on the home page.
http://www.cinetechonline.com/index.html

Backfocus took my breath away
 

I was testing some stuff today and put the 16x manual on today to try this breathing thing.

I did notice, if you use the backfocus ring to focus, it does not breathe. There was stuff in my living room that was some eight feet away from each other and it worked. This wasn't a real super-duper test, and the backfocus isn't a very suttle control, but if you are trying to do something goofy it has a cool effect (it was like Duke reaching for the mace can during _Fear and Loathing in Las Vegas_...)

(sorry if this is common knowledge, but noone else mentioned it :)

Uhhhh, nope. Been a while since I've seen the movie. I think I was tripping when I saw it :~)

That won't work because you'll be spending all your time trying to get the back focus corrected. Nice try. Once you set the back focus, it's best not to muck with it. I want to be able to use my follow focus rig so that I, or my 1st AC can pull focus, reliably, repeatedly, take after take. If I have to rack focus, I'll take the minute to switch over to the 20x auto lens as we prep for that shot. I have a gear ring for the 20x from Cine Tech, so I can use my ff rig. I've already had to do the switch a few times.

We were somewhere around Barstow on the edge of the desert when the drugs began to take hold. I remember saying something like “I feel a bit lightheaded; maybe you should drive...” And suddenly there was a terrible roar all around us and the sky was full of what looked like huge bats, all swooping and screeching and diving around the car, which was going about a hundred miles an hour with the top down to Las Vegas. And a voice was screaming: “Holy Jesus! What are these goddamn animals?”...

...Wait! We can't stop here! This is bat country!

Then maybe you are more familiar with the scene from _Earnest Goes to Jail_ when the gents are talking across the room and the toaster pastry pops up in front of the camera (which Bobby then shoots with a .45). That was a nice pull :) "Burn 'em!!!"

I agree messing with backfocus is bad hat. But if your are recording stuff like gingerbread target practice and drugged-out attourneys then you're already breaking the rules, why not get the shot. I can definately see myself putting some tape marks on that ring and telling the audience "lets look HERE now..." :D

All this talk kind of makes me wonder how the 20x can do this with no problem. There's video glass that won't breath but I think it's more commonly heard in the same sentence as "DigiBeta" or "broadcast". The 20X glassware is nice but not five digit price tag nice. My uneducated guess is it's adjusting the zoom when you spin the focus ring. That doesn't sound too hard when both controls are already servo'd; you just need to write a table containing the known degree of breath error at varying zoom settings, then touch the zoom slightly whenever some operator spins the focus ring.

All zoom lenses breathe some, and most primes do too, except for the really, really expensive ones

I wish I were more familiar with the manual lenses you guys are talking about. But even though I am not, I just wanted to mention the "trick" which is similar to moving the back-focus, but without the same potential calibration consequences. And that is - to use the Macro to do focus racks.

Do the 14x and 16x manual lenses have a macro adjustment?

I also seem to remember that the degree of breathing in lenses has something to do with wether focus adjustment occurs outside or inside the lens. That is to say that lenses where the whole focus barrel turns when focusing; breath more than ones where the elements inside the barrel move without the entire barrel rotating. There are some lenses that actually get longer when you change the focus. Do these breath more than the others or less?

Daniel K -
Yes the 16x does have Macro, not sure about the 14x. Your trick is cool but macro is kind of a small-ish range at the end of the ring. I admit I didn't try the macro lock for what I did, I just turned the whole ring.

Out of curiosity, is it a big deal to loose your back focus calibration? When I was done playing I just centered the front focus, pointed across the room, brought the back somewhere close then fined with the front. I'm asking cuz I really don't know, it seems like if you weren't supposed to change your backfocus they wouldn't put a ring there (but then good luck getting bayonet adaptors to work lol :)

What happens when your back focus is out of wack is that the focus will change when you zoom. That means zooming in for focus is no longer accurate. It's a pain to get this re-adjusted because you can only do this by trial and error. And you need something which shows exact focus in the wide angle end of the lens. That is difficult to exactly determine because everything looks sharp at the wide angle end. There is a special pattern that you is good for checking this, called a (seemansstern in Germany)... man I've been away from home too long ... I don't know what it's called in English (sea mans star?).

I don't know if there are other things that can be adversely effected by incorrect back focus, like lens markings not being accurate, but there may be.

Back focus is there, because, in this imperfect world, sometimes the distance from the lens to chip can vary from one camera to another, or can change over time. Especially if you use the camera a lot and hard.

I hope that this makes sense.

Mark, and all. Are you saying that with the XL2 follow focus rig, on a NON manual canon lens, it will hit the marks and pull acurate focus despite these crazy spinning barrels?

Daniel, yes that does help, thanks. So when you get proper back focus set up, can you mark it somehow, and it will remain accurate? (except for chip drift, camera/lens wear and etc). That way after a goofy focus trick you could easily restore the correct setting.
We use a wide angle adaptor on a movie's JVC that requires back focus adjustment every time you install it, I don't know how the director keeps it straight.

If you dick with the back focus you'd better have a decent sized monitor at hand because markings are a ballpark indicator - there is a fairly critical point of focus, particularly if you're going to the big screen or are zooming in on a subject and then pulling back out and expecting to hold critical focus. On set is not where I'd choose to start mucking with back focus, there are alternatives.

I would tend to agree with Bill. The adjustment can be very tiny, sometimes. And it is possible that things like; if you move the back-focus ring counter-clockwise it will change the back-focus differently than if you turn it clock-wise. Making marks useless. The ring is not made to be used in the way you are suggesting. I think the idea of doing a rack-focus this way is brilliant as a last ditch solution. But I wouldn't recommend it as a standard MOA. Unless you have another "standard" lens which you can use for all the other shots. One "tricky" lens and one "Safe" lens.

<<<-- Originally posted by Bill Anderson : Mark, and all. Are you saying that with the XL2 follow focus rig, on a NON manual canon lens, it will hit the marks and pull acurate focus despite these crazy spinning barrels? -->>>

Bill, yes the 20x auto lens will be able to hit focus marks because as part of the Cine Tech follow focus kit I got, there is a geared ring to go around the lens' focus ring. That interfaces with the gear on the follow focus drive. That's how a ff works, once the gears are enmeshed, you can repeatedly hit your focus marks and do pulls. The Cine Tech Titanium SL has a moving stop on the outer part of the focus wheel that will hit the witness mark arm, thereby stopping the focus. www.cinetechonline.com

I am trying to figure out how to prevent the zoom and focus rings from spinning forever, but that is most likely some type of physical modification on the ring to make them stop. I will post about that later.

<<<-- Bill, yes the 20x auto lens will be able to hit focus marks because as part of the Cine Tech follow focus kit I got, there is a geared ring to go around the lens' focus ring. That interfaces with the gear on the follow focus drive. That's how a ff works, once the gears are enmeshed, you can repeatedly hit your focus marks and do pulls. . -->>>

Hi Mark. This is very interesting, but I always thought that the amount of focus adjustment on this lens varied with the SPEED of turning as well as the angle (of course I could be wrong about this). Have you actually confirmed that this attachment works consistently even if you turn it at different speeds? Thanks.

Richard

Yes, I do it every day. The speed at which you turn, doesn't matter, you just achieve focus faster, or slower. I am talking about focus, NOT zoom. If you have seen a follow focus, or used one, you'll know what I'm talking about.

http://www.zacuto.com/Chrosziel%20%20follow%20cine.htm
For an idea of what a follow focus looks like, check out the photo of the Chrosziel follow focus on a video camera (Sony?[random pic I grabbed for illustration]). This may help if you've never seen one before.

This thread is for the 16x manual lens. Look at the focus ring and you will see distance markings on the focus ring. These are repeatable with or without a follow focus. Six feet is six feet on that lens. A follow focus just makes it easier to hit the marks accurately. In the Zacuto picture, the big white disc is for writing your marks. Turn the big knob and the gear turns the lens' focus ring. There is a witness mark just above the white disc at 12'clock. That never moves but the disc does and so you can see when you're on the mark. Note that usually the First Camera Assistant is pulling focus while I operate the camera.

We're getting a bit off topic. Do some research and you will find pics and see how it's used.

Mark,
You have given the impression that the follow focus works on the 20x servo lens. I think that is what we are asking. It is obvious that it works on the 16x manual but some of your comments sound like you have been able to make it work on the servo. IS this so? I know there are limitations if it does but even getting it to work consistently at all is a big plus.

And I second the theory that the servo is both speed sensitive and motion sensitive. Meaning a movement of 1 inch slowly will give one focus result and a movement of 1 inch fast will focus farther.

Any thoughts?

Cine tech makes a gear ring for the 20x auto lens. I have it and I'm not afraid to use it.

No, the fast/slow thing does not apply. I don't know what you are talking about.

Click on the link below and see what I'm talking about:

http://www.cinetechonline.com/

I have to go and finish my pizza and wings (too much fat and grease)...

Okay, I've mucked around doing it fast and then slow. No difference.

P.S. Have y'all been following the links I've been making? They're dynamic. I thought for sure I've made a bunch on this thread.

So if you stay within the range of the focus and don't turn it beyond the point where the focus ring spins but the lens has stopped it is completely repeatable?

If that is the case then hooray! I was under the impression that the darn thing was speed sensitive? So you can mark focus points and hit them them repeatedly as long as you don't exceed the max and minimum focus of the actual lens? I understand that the thing would be all messed up if you hit autofocus or turn it off but for that particulat session you could count on it?

<<<-- Originally posted by Marty Hudzik : So if you stay within the range of the focus and don't turn it beyond the point where the focus ring spins but the lens has stopped it is completely repeatable?-->>>

Yes, the follow focus has a stop so you don't go beyond.

<<<-- If that is the case then hooray! I was under the impression that the darn thing was speed sensitive? So you can mark focus points and hit them them repeatedly as long as you don't exceed the max and minimum focus of the actual lens? I understand that the thing would be all messed up if you hit autofocus or turn it off but for that particulat session you could count on it? -->>>

If you were to turn on AF it would probably cancel your marks and you would have to reset them. I'm not going to mess with it now, I have to go to sleep and wake up in a few hours. I'm in manual focus pretty much all the time.

I never use anything but manual focus either. But I am trying to think of things that would mess up the calibration if you will.

Thanks.

Mark, thanks for the confirmation. I tried the link you provided, but can just see a huge list of bits and pieces that I can't make much sense of. How do you know which bits you need to buy to make up one complete follow focus unit? (Hopefully not ALL of them!) Is there a follow focus KIT somewhere that is easier to understand?

Richard

I just looked at the cinetech link as well. The picture they have on the home page shows the follow-focus being used on a XL-2. I wonder if there is something about the 20x servo lens for the XL-2 that makes it possible to hit marks. That deffinateily is not the case with my 16x servo. Too bad!

Does anyone know what they changed on the 20x servo, to make the focus ring direct drive?

Maybe we should make a new thread.

The 16x manual can hit the same marks with or without a follow focus because it's mechanical. The 20x auto lens is all electric, I believe. I will get confirmation on this, but after a few conversations with people, I'm beginning to get the idea that the 20x drive mechanisms for both the zoom and the focus are electric, rather than a mechanical linkage. That's why the the feel is different and that may explain why some peple are reporting focus effects dependent upon speed of the focus ring being turned. That is probably why there are no permanent markings for focal length or focus distance.

So, I'm waiting for Canon to come out with a full set of prime lenses for the XL2, similar to the FJs HD prime lenses line for 2/3" HD cams and some super-wide zooms with more than a 3x range. 2mm-60mm?

http://www.usa.canon.com/html/indust...me_lenses.html








Okay, any time now...



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