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cine lens for 3700 Varicam


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#1 David Coleman

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Posted 05 November 2010 - 03:36 PM

I'm looking at purchasing a 3700 Varicam to replace the 27H that we currently have. We have a Fujinon 3.5x13 zoom (2/3" format) currently, but is it possible to get a zoom lens for a more cine depth of field that is as versatile as the Fuji we currently have? I understand the limitations of the small imager, and I know what I'm really asking for is more like the DSLR look, but let's rule that out for the moment. Is there something in-between? What lenses would be used for episodic TV?

I don't have a A/C and would like to avoid lens changes if possible.
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#2 David Mullen ASC

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Posted 05 November 2010 - 04:02 PM

I'm looking at purchasing a 3700 Varicam to replace the 27H that we currently have. We have a Fujinon 3.5x13 zoom (2/3" format) currently, but is it possible to get a zoom lens for a more cine depth of field that is as versatile as the Fuji we currently have? I understand the limitations of the small imager, and I know what I'm really asking for is more like the DSLR look, but let's rule that out for the moment. Is there something in-between? What lenses would be used for episodic TV?

I don't have a A/C and would like to avoid lens changes if possible.


Putting a cine zoom on isn't going to change the depth of field characteristics -- that's determined by the focal length, distance focused, & f-stop, and the field of view (that affects your choice of focal length) is determined by the size of the imager, so 20mm at f/4 (let's say) on the Fujinon zoom will give you the same view and DOF as 20mm at f/4 on a cine zoom out onto the Varicam. In fact, the main difference is just that the ENG zoom has extra features like auto exposure and a built-in zoom motor, whereas a cine zoom would require a separate zoom motor and control put into the matte box rods.

The primary thing that would give you a shallower-focus look is to shoot at a wider f-stop, and in fact, you are more likely to find an ENG zoom that opens to f/2.1, for example, than a 35mm cine zoom.

The other thing would be to use a 35mm lens adaptor like a P&S Technik or something, where the 35mm image circle of the lens is projected onto a groundglass in the adaptor and rephotographed by the smaller sensor, but that's adding a whole layer of complexity that you don't want to deal with.

In fact, if you don't have an AC then a cine lens is the last thing you want to deal with as a Varicam shooter, they are all-manual and generally need an AC along with a follow-focus unit, a zoom motor, etc. Plus 35mm cine zooms are generally a lot heavier and larger and slower.

DSLR's are also problematic for the ENG/EFP shooter because of the lack of ENG-style video zooms. And shallow depth of field just makes everything harder for an operator who is pulling his own focus. Honestly, if you really want to shoot with a lot of shallow focus all the time, get a focus-puller.

The other problem with just sticking a cine lens directly onto a Varicam is that the optics weren't designed to focus evenly onto a prism block splitting the light to three sensors as a B4 video lens would be.
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#3 David Coleman

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Posted 05 November 2010 - 04:28 PM

David,
Thanks for taking the time to explain that. I have a lot of experience with the video lenses, but even with a wide open aperture I can't get the DOF and selective focus that I want. I know, join the club.
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#4 David Mullen ASC

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Posted 05 November 2010 - 05:37 PM

David,
Thanks for taking the time to explain that. I have a lot of experience with the video lenses, but even with a wide open aperture I can't get the DOF and selective focus that I want. I know, join the club.


A 2/3" imager gives you the equivalent depth-of-field of stopping down a 35mm cine camera by 2.5-stops. So f/2 on a 2/3" camera looks like an f/4.0-5.6 split on a 35mm cine camera in terms of depth-of-field due to the focal length being 2.5X shorter to match field of view at the same distance and same working f-stop.

So if you want less depth of field than that (the fastest B4 lenses are around f/1.6), you have no choice but to use a larger imager / sensor, or some sort of depth-of-field lens adapter like those by P&S Technik or Redrock, etc. where the groundglass screen becomes the defactor larger imaging area.

Personally I don't think f/2 on a 2/3" camera is all that deep-focus looking, especially as soon as you go in for close-ups. It's only on wider-angle medium and wide shots where you can't really achieve a shallow-focus look.

For dramatic narrative purposes, which mainly involve following actors around a room talking in close-up these days, f/2 is plenty shallow enough to already be a challenge for a focus-puller. The only projects that need even shallower-focus than that are more "arty" music videos and commercials, etc. that want that visual look more than they care about actors always staying in focus. And since you said that you don't have an AC, I wonder why you want to burden yourself with such difficult focusing situations without a skilled focus-puller. 35mm focus-pulling is a real challenge, which is why the best focus-pullers are in such high demand.
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