Premium Member Tim Carroll Posted February 24, 2004 Premium Member Share Posted February 24, 2004 Had the weirdest experience last night on a shoot. Using a Canon XL1S with a Canon 14x manual focus lens, camera locked down on a tripod, back focus set. Was at the telephoto end of the zoom range, focused on an actress on stage. Did fine focus, everything was cool. We are filming along (or videoing along I guess) and I started noticing the lens going slightly in and out of focus. No one was touching the camera or lens and the actress was not moving back and forth. It was really strange and the first time I have ever noticed that. Anyone have an idea what was causing that? Thanks, -Tim Link to comment Share on other sites More sharing options...
Rob Belics Posted February 24, 2004 Share Posted February 24, 2004 IIRC, that is a feature of the xl1. If you breath too hard the ring will rotate. Unless you have it on auto focus? Link to comment Share on other sites More sharing options...
Premium Member Tim Carroll Posted February 24, 2004 Author Premium Member Share Posted February 24, 2004 Rob, thanks for the reply but I think you misread my post. I am not using the lens that came with the camera, the autofocus lens, I am using the Canon 14x manual focus lens. There is no autofocus. It is an older lens, one from the Canon Pro line that they converted to work with the XL1. -Tim Link to comment Share on other sites More sharing options...
Mitch Gross Posted February 24, 2004 Share Posted February 24, 2004 Don't know what was going on there, other than faulty gear. I'd have to see it to know. This is not lens breathing. That is when you adjust focus and the image appears to zoom slightly. Depending on the lens design and focal length this effect can be quite pronounced. Link to comment Share on other sites More sharing options...
Leon Rodriguez Posted February 26, 2004 Share Posted February 26, 2004 Mitch, Is lens breathing a mechanical or optical phenomena? I haven't come across it, but it would be nice to be prepared for that. No ideas on Tim's experience from here. Link to comment Share on other sites More sharing options...
Premium Member Kevin Zanit Posted February 26, 2004 Premium Member Share Posted February 26, 2004 ::: I haven't come across it::: All lenses breathe to some extent. Older lenses are more prone to this. I believe (I could be wrong) that it is an optical problem. Breathing tends to become more noticeable with larger focus pulls. Kevin Zanit Link to comment Share on other sites More sharing options...
Mitch Gross Posted February 26, 2004 Share Posted February 26, 2004 It's an "optical/mechanical" problem. ;) Basically when changing focus you are changing the distance between lens elements to shift their focus points. But any lens that isn't an optical flat has a magnification factor, so as you move the glass the image size changes. More advanced lenses move multiple elements in relation to one another so that they can shift focus without alterring the image magnification, or at least minimize it. Adjust the focus on any still camera lens and you'll see this happen. There's no reason not to allow the image size to shift on a still lens so they don't bother. Zoom lenses have a lot more elements doing a lot more work, so you'll see the effect more pronounced in them compared to primes. Link to comment Share on other sites More sharing options...
Leon Rodriguez Posted February 27, 2004 Share Posted February 27, 2004 OK, now I understand what you are talking about. A zooming while in the process of focusing not from a static already focused set up. Sure. I'm with you now. This is not what happened to Tim, right? His lens lost focus in a static position. Curious. Link to comment Share on other sites More sharing options...
Jason Mann Posted February 27, 2004 Share Posted February 27, 2004 This might not be true with your lens, but I know the manual lenses I've used with the XL-1 have still had an AF option. Maybe it was AF? But I doubt it, because usually the AF is pretty jarring when it starts searching for something, and it sounds like your problem is more subtle than that. Wow. I guess that's totally unhelpful. Sorry. Link to comment Share on other sites More sharing options...
Mitch Gross Posted February 27, 2004 Share Posted February 27, 2004 The true manual focus lens is manual only. The lenses you are describing are AF with the auto-focus switched off. Adjusting the focus on these lenses simply activates a servo mechanism which then adjusts the focus, making it impossible to set numerical measured focus marks. Link to comment Share on other sites More sharing options...
Jason Mann Posted February 27, 2004 Share Posted February 27, 2004 The lens I mean is a Canon lens that's black in color and marketed specifically as a manual focus lens for the XL-1. It has true focus marks (i.e. endstops like a normal lens, not the endlessly spinning focus ring) but also has a servo control for the zoom and, I think, an AF switch on the barrel. I know this lens exists, but I'm not sure it's the one he's describing. (Maybe I'm thinking of the servo switch for the zoom and the lens doesn't have AF. I don't know.) Link to comment Share on other sites More sharing options...
Mitch Gross Posted February 28, 2004 Share Posted February 28, 2004 (Maybe I'm thinking of the servo switch for the zoom and the lens doesn't have AF. I don't know.) That is what you're thinking. Basically a miniature version of a professional industrial video lens. Controls for the zoom and iris but the focus is completely manual. Link to comment Share on other sites More sharing options...
Guest Ultra Definition Posted February 28, 2004 Share Posted February 28, 2004 If the camera was set to auto exposure and the F stop was changing, then DOF was changing so things could go out of focus. It would have been even worse if you had checked the DOF with a less open iris and then shot with a more opened one, which would lower the DOF. Link to comment Share on other sites More sharing options...
Tim Tyler Posted March 4, 2004 Share Posted March 4, 2004 A zooming while in the process of focusing not from a static already focused set up. Breathing is not restricted to zoom lenses, although it is often most noticable on zoom lenses. Even if the lens is of fixed focal length (prime lens) changing focus can make the image appear to zoom in or out slightly. That's "breathing". Link to comment Share on other sites More sharing options...
Leon Rodriguez Posted March 5, 2004 Share Posted March 5, 2004 Thanx Tim. Good info. Link to comment Share on other sites More sharing options...
Joshua Csehak Posted December 27, 2009 Share Posted December 27, 2009 Not that I'm not replying from 5 years in the future, but check out the scene in Star Wars where Vader interrogates Leia in her cell with the syringe droid. The lens breathes when they rack focus, and it looks pretty cool and ominous. So it's not necessarily a bad thing... Link to comment Share on other sites More sharing options...
Premium Member Bill DiPietra Posted December 28, 2009 Premium Member Share Posted December 28, 2009 Zoom lenses have a lot more elements doing a lot more work, so you'll see the effect more pronounced in them compared to primes. I had this on the first 16mm film I shot in college. I was shooting the credits off the wall and when I got the film back, it looked as though there was some rough and minimal zooming going on. I knew I hadn't zoomed, so I figured it was a lens issue. I was using an old Angeneiux 12-120mm. Thanks for the explanation, Mitch. And Happy New Year!!! Link to comment Share on other sites More sharing options...
Premium Member Keith Walters Posted December 28, 2009 Premium Member Share Posted December 28, 2009 Not that I'm not replying from 5 years in the future, but check out the scene in Star Wars where Vader interrogates Leia in her cell with the syringe droid. The lens breathes when they rack focus, and it looks pretty cool and ominous. So it's not necessarily a bad thing... In a nutshell, you've just pointed out the difference between an artist and a paint-by-numbers wannabe. It's entirely possible that they noticed the "defect" in the rushes for that scene but like you, thought it looked pretty cool and left it in, where lesser stature and hence more insecure cinematographers might have wasted more of the backers' money on a reshoot. I couldn't tell you how many times I've seen that sort of thing happen. Bleach bypass must have started life as an accident. I'm sure the "snap-micro-zooms" that are so popular at the moment in episodic TV started out with somebody accidentally bumping something and liking the effect. I personally think the dreaded "rolling shutter" effect you get with CMOS cameras looks pretty cool with the right type of shot, and really don't believe the average cinema-goer would ever notice it most shots anyway. I guess the bottom line is that the only reason for rejecting any photographic "mistake" is that you don't like the look of it, not simply because it's "not done". Link to comment Share on other sites More sharing options...
Fred Neilsen Posted December 28, 2009 Share Posted December 28, 2009 I personally think the dreaded "rolling shutter" effect you get with CMOS cameras looks pretty cool with the right type of shot, and really don't believe the average cinema-goer would ever notice it most shots anyway. I guess the bottom line is that the only reason for rejecting any photographic "mistake" is that you don't like the look of it, not simply because it's "not done". http://www.flickr.com/photos/phirleh/3655557511/ The maker of the video likes it "I love the strange artifacts you get out of the d90's rolling shutter." Link to comment Share on other sites More sharing options...
Joshua Csehak Posted January 14, 2010 Share Posted January 14, 2010 Yeah, definitely. And of course, one of the most famous examples: http://www.masters-of-photography.com/L/la...e_car_trip.html omg I'm so sick of those micro-snap-zooms! It's like, "Sir, we got the forensics back from the lab." "Hand 'em over. My God." Micro-snap-zoom! "What is it?" Micro-snap-zoom! "The lab technician forgot to initial the manifest." Micro-snap-zoom! "Get him on the phone, stat." Micro-snap-zoom on the phone! etc... Link to comment Share on other sites More sharing options...
Jim Hyslop Posted January 17, 2010 Share Posted January 17, 2010 It's entirely possible that they noticed the "defect" in the rushes for that scene but like you, thought it looked pretty cool and left it in Just to play Devil's Advocate - or maybe the producer said "Nope, no budget for a reshoot" so they left it in and hoped nobody would notice :-D -- Jim Link to comment Share on other sites More sharing options...
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