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What does 35mm DOF adapter do?


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#1 Gabe Agoado

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Posted 15 October 2016 - 12:33 AM

I'd like to get one of these, I understand the basic concept but there are a couple of things I am uncertain about. I understand that I will have to zoom in on my primary lens to see the focusing screen, and then I will be attaching a secondary lens to the other end.

 

If I attach a 24mm secondary lens will I be able to get a wide angle of view or is the focal length effected by how far I have to zoom in on the primary lens?

 

Will I get vignetting if my primary lens is 72mm and then I step it down to 55mm to fit the adapter or does zooming in with the primary lens make that not matter?

 

 


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#2 Jay Young

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Posted 15 October 2016 - 05:03 AM

Why do you want to get one of these?

 

Is there something that you can not achieve with your current camera (owned or rented) that this will allow you to achieve?

 

They were pretty terrible back in the day, and I haven't seen one used in at least 8 years. 


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#3 Gabe Agoado

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Posted 15 October 2016 - 08:58 AM

Hi,

 

I was hoping to experiment with this on a smaller sensor camera. I know there are a lot of ways to get shallow DOF without using an adapter so just want to know If I'm probably wasting my money.


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#4 David Mullen ASC

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Posted 15 October 2016 - 09:51 AM

I only used one once on a 2/3" Varicam years ago, but in theory you are zooming in so that the ground glass inside the adaptor fills your frame and then the image from the second lens fills the ground glass so what sort of lens coverage you get just depends on if the ground glass is S35 or FF35 sized and which your secondary lens was designed for in terms of vignetting. The field of view should be for whatever the ground glass was designed for.

As for whether you need an adapter to get shallow focus depends on how small your sensor is -- 2/3" video is about 2.5-stops deeper than Super-35 which is within a realm where using an f/2 lens would be like shooting at an f/2.8-4 split in Super-35... whether that's shallow enough is a matter of taste. But a 1/3" sensor is more like 5-stops deeper than Super-35 so it's pretty hard to get a shallow focus effect.
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#5 Brian Drysdale

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Posted 15 October 2016 - 02:44 PM

Other than a shallower DOF, the most noticeable effect was it seemed like you were using a promist or similar filter.


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#6 Gabe Agoado

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Posted 15 October 2016 - 03:19 PM

Thanks.


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