Focus issue

Brian Rose · March 30, 2014

Guys and gals I could use some advice. I got some test footage back on my Eclair S16. I'd just gotten it back from Bernie O'Doherty, who is pretty much tops when it comes to camera servicing. He gave the whole cam a service, including lens collimation and even brightened the viewfinder. Well the test footage has a real problem in that it loses focus when I zoom out. But it looked sharp in my viewfinder, which is really problematic to me, that what I could be seeing is sharp, but what I'm capturing isn't. For my purposes I need my camera to be reliable in this regard, because I won't have every opportunity to stop and measure every scene. What could be causing this? Perhaps did I not have the lens seated properly? I make sure the cam is good and tight, and locked in the turret, but maybe something was loose? Or is this just inherent to a varifocal lens? But even still if I'm set to infinity, shouldn't distant objects have remained in focus when I zoomed out? I even went as far as to use a DIY focusing glass (using some translucent paper) taped to the gate, and adjusted focus, the image looks sharp. I'm stumped! The lens is a Canon Super 16 14-80 1:2.0. The film was 500 ASA shot at 2.0.

Here's a sample clip of the issue I'm having:

https://vimeo.com/90475142

Adrian Sierkowski · March 30, 2014

I'm not familiar with the lens, but perhaps it isn't parafocal? If that's the case, then it wouldn't hold focus through zooms; but would really be more like a variprime. The fast speed too leads me to think this is a possibility.

Jean-Louis Seguin · March 30, 2014

Obviously, your lens is not collimated properly.

I've never heard of a 14-80mm Canon lens.

Jean-Louis

Brian Rose · March 30, 2014

Obviously, your lens is not collimated properly.

I've never heard of a 14-80mm Canon lens.

Jean-Louis

Sorry, it's a 14-84 zoom.

I suspect as much but was sure Bernie did a lens collimation, since I included it with the cam when I had it serviced. He's top notch, so maybe it wasn't included, and I was erroneous.

Is there anything I can do, or must I ship this off (again) to be serviced???

Brian Rose · March 30, 2014

Okay so to provide a little more info: I set up my camera on tripod pointed at a focus chart. And I tested it at 4, 5, 6, 7, 8 and 12 feet...and when I focused by eye, and arrived at a sharp image, I looked to my focus ring and it was dead on the 4, 5, 6 ft markers and so on. It was remarkably good. As was infinite focus...when zoomed all the way in. And when I zoom out wide, everything still looks sharp...so why did my stuff lose focus when I zoomed out?

I mean I understand what a parfocal and varifocal zoom lens is, that the latter must be readjusted upon zooming in and out, but if I'm set to infinity zoomed in and everything is sharp, shouldn't it remain so when I pull back wide, but remain set at infinite focus? How could it be that it looked sharp in the viewfinder, yet came out soft? I'm stumped!

Dom Jaeger · March 31, 2014

Hi Brian,

the lens should be parfocal, according to this post by Leo Vale:

http://www.cinematography.com/index.php?showtopic=21327

that zoom was the first S16 conversion, not many around. From memory they were originally Canon TV zooms. It'd be from the late 60s early 70s so not very modern, probably not great wide open, but should hold focus if properly collimated. I can't watch Vimeo clips on this computer, but if you shot your test wide open at night it could just be that fine detail gets smudgy at the wide end.

With any reflex film camera, the ground glass depth (viewfinder focus) is a different setting to the flange depth (gate focus), so you can have something in focus through the viewfinder but out of focus on the film. But it seems unlikely if the camera was just serviced.

If the lens is slightly out of collimation the focus marks will still line up at the long end, but things will get soft as you zoom out to the wide end. Judging exact focus at 14mm can be tricky just through a viewfinder though.

I would call Bernie and talk about it, maybe the lens wasn't calibrated, maybe something went out of tolerance during transit, maybe the lens has issues. Do you have a local rental house that would let you throw it up on a lens projector to assess it? It could be worth shooting another test with a good prime.

Brian Rose · March 31, 2014

Hi Brian,

the lens should be parfocal, according to this post by Leo Vale:

http://www.cinematography.com/index.php?showtopic=21327

that zoom was the first S16 conversion, not many around. From memory they were originally Canon TV zooms. It'd be from the late 60s early 70s so not very modern, probably not great wide open, but should hold focus if properly collimated. I can't watch Vimeo clips on this computer, but if you shot your test wide open at night it could just be that fine detail gets smudgy at the wide end.

With any reflex film camera, the ground glass depth (viewfinder focus) is a different setting to the flange depth (gate focus), so you can have something in focus through the viewfinder but out of focus on the film. But it seems unlikely if the camera was just serviced.

If the lens is slightly out of collimation the focus marks will still line up at the long end, but things will get soft as you zoom out to the wide end. Judging exact focus at 14mm can be tricky just through a viewfinder though.

I would call Bernie and talk about it, maybe the lens wasn't calibrated, maybe something went out of tolerance during transit, maybe the lens has issues. Do you have a local rental house that would let you throw it up on a lens projector to assess it? It could be worth shooting another test with a good prime.

And Dom maybe that is the issue is that I didn't have the viewfinder set properly. I'm pretty nearsighted so I have to adjust it for my eyes so I can look through without glasses. Maybe it was off and I didn't realize it. Because I some other footage I shot, with some really focus critical stuff (with a diopter for close ups) came out perfectly. I just hate that i can't replicate the problem.

Alas I there aren't rental houses around to speak of, at least, ones that rent film gear any more. They're all digital now. I'm not sure they'd be able to take my mount type.

Dom Jaeger · March 31, 2014

If your eyepiece was incorrectly set you would get soft pictures when zoomed in as well.

Was the other, perfectly sharp footage shot at the wide end of the zoom, or at full aperture? Remember, if the lens collimation is a bit out you'll notice it most at full aperture and shortest focal length. Full aperture will also bring out all the aberrations of the lens, which for a zoom this old at f/2 could be pretty noticeable and make things look soft. I'd stop that zoom down at least 2 stops if you want decent pictures.

Speak to Bernie about whether he checked the zoom over. There could be play in the mechanics (zoom or focus) that could introduce intermittent focus problems too.

Brian Rose · March 31, 2014

If your eyepiece was incorrectly set you would get soft pictures when zoomed in as well.

Was the other, perfectly sharp footage shot at the wide end of the zoom, or at full aperture? Remember, if the lens collimation is a bit out you'll notice it most at full aperture and shortest focal length. Full aperture will also bring out all the aberrations of the lens, which for a zoom this old at f/2 could be pretty noticeable and make things look soft. I'd stop that zoom down at least 2 stops if you want decent pictures.

Speak to Bernie about whether he checked the zoom over. There could be play in the mechanics (zoom or focus) that could introduce intermittent focus problems too.

Thanks for the advice. I'll talk to Bernie tomorrow. And I've got another lens on order that came well recommended. I need a fast lens for my documentary, and this one is a 22.5-70 that opens to a 1.5.

I may wind up bagging the other lens...it's just proving too problematic to rely upon.

Brian Rose · March 31, 2014

If your eyepiece was incorrectly set you would get soft pictures when zoomed in as well.

Was the other, perfectly sharp footage shot at the wide end of the zoom, or at full aperture? Remember, if the lens collimation is a bit out you'll notice it most at full aperture and shortest focal length. Full aperture will also bring out all the aberrations of the lens, which for a zoom this old at f/2 could be pretty noticeable and make things look soft. I'd stop that zoom down at least 2 stops if you want decent pictures.

Speak to Bernie about whether he checked the zoom over. There could be play in the mechanics (zoom or focus) that could introduce intermittent focus problems too.

And to answer your question, the other stuff was at full aperture (my documentary involves some dark settings and I'm testing stocks and push processing), but it was captured at the longest focal length.