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redrock micro adapter depth of field chart


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#1 chris marte

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Posted 07 May 2008 - 11:58 PM

Hey everyone. I've been hired by a small production company to shoot some local sports events later this month. They're providing me with a Canon XL-2 mounted with a Redrock Micro 35mm adapter, with 4 Canon FD prime lenses: 28mm, 50mm, 100mm and 200mm. Now i've shot with adapters before, but what always bothers me is that adapters make the f/stop and distance markings on the camera's lenses false, and that DOF charts for a camera don't apply when an adapter is used on them. That in particular is a problem for me, since I love to use DOF charts, because they help me plan shoots and keep me organized. So, Is there any place where i can find a Canon XL-2 with a redrock micro adapter DOF chart? Or is there an equation i can use to calculate how much different DOF will be with the adapter on the XL-2 as compared to with it off?
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#2 Allen Achterberg

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Posted 08 May 2008 - 02:40 AM

The groundglass can be adjusted on the Red Rock, therefore the witness marks can be correct. I have done this to several units.

First, You need to learn to ignore the Camera's settings. Do not use the Camera's Focal Length or F-Stop to determine Depth of Field, think of it more of a way to fine tune your ASA. Ignore the camera. Everything that has to do with the DOF you'll be using will be in front of the Camera, the Lenses on the Red Rock. Assuming you adjust the Red Rock ground glass, and have correct witness marks you can use standard depth of field charts applying the lens length and f-stop. Your result will be satisfactory. If you leave it as is your results will be confusing. I advise you to mess with the red rock.

Determine if the ground glass is too close or too far from the back element. I do this by setting the lens to infinity, and then adjust the groundglass so the infinity is correctly in focus. Then I checked the witness marks and they were correct. If you need more guidance, let me know, I'll help you further.

Are you pulling your own focus and operating???

Best
Allen
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#3 Michael Nash

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Posted 08 May 2008 - 09:42 AM

The whole point of using a 35mm relay adapter is to get the depth of field characteristics of the 35mm lenses you mount on it. The 35mm lenses project an image onto the groundglass, and the video camera's lens re-photographs that. The 35mm lenses are what give you the depth of field, not the camera's lens.
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