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Old September 12th, 2008, 12:01 PM   #1
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How does 16mm dof compare to video cams?? 16mm dof adapter??

We all want our video cams to have 35mm dof, but I was wondering today how dof from a 16mm cam compares with todays video cams?

I realise dof is dependant on sensor (or film) size, but if the two were the same, would they both have equal dof characteristics? or would the video cam still be different by design?

The trail of thought led to...what If we made an adapter that utilised 16mm lenses. would we still have the same problems of 'hot' centres and vignetting around the edges. The image would be smaller and therefore sharper??

Let me know what you think
James
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Old September 12th, 2008, 03:42 PM   #2
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I think you'll find that hot spots and vignetting will be even more of an issue with 16mm. As you mentioned the image would be potentially smaller, which would mean that also the hot spot would be smaller. It would require you to zoom in even more, etc.

I wanted to avoid those issues so I recently built a 70mm mid-format spinning adapter. It allows me to eliminate vignetting all together. The hotspot is so much larger that it fills the frame nicely.

You can see the results for your self. There is a thread about it in the dvx forum along with a video example:

Mid-Format DOF Adapter
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Old September 13th, 2008, 12:25 AM   #3
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With a 16mm sized groundglass image, you are up against a wall resolution-wise because of the scale of groundglass particle size versus the image size.

In the JVC KY-F50, an older compact 1/3" 3xCCD SD broadcast quality camera head, the facility to fit up 2/3" C-mount camera lenses and represent their true field-of-view was achieved with a built-in purely optical relay system.

I understand (maybe wrongly) that the Super16mm adaptor for the JVC GY-HD--- camera family is also a similar purely optical solution.

The optical depth of field/field of view characteristics of Super16mm would be comparable to the 2/3" TV-safe image area from a practical viewpoint.

Treat my comments with some disdain as I am no optical engineer.

Last edited by Bob Hart; September 13th, 2008 at 12:28 AM. Reason: errors
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Old September 14th, 2008, 12:54 AM   #4
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Quote:
Originally Posted by James Millward View Post
We all want our video cams to have 35mm dof, but I was wondering today how dof from a 16mm cam compares with todays video cams?
S-16mm DoF characteristics are roughly the same as a 2/3" CCD.
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