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Creating Lens File on Set (White Shading Problems)


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#1 Emanuel Schwermer, bvk

Emanuel Schwermer, bvk
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Posted 08 June 2006 - 10:47 AM

Hello everybody,

I have a question concerning white shading, let us say with an Sony HDW 750 Body.
Imagine you are shooting a commercial for about a week.
You checked all your Gear @ the rental house a day long and the rental house provided proper Lens Files for your Zooms or what ever.
At the third day the DP is asking for a T-Rex Snorkel to shoot car interiors the next day.
No problem, your HD rental house calls a Film rental house and is ordering a T-Rex Snorkel System with Sony B4 Mount (there is a Sony Mount Adapter what you can purchase with the T-Rex from P+S Technik).
In the morning you set up your camera with the T-Rex like you ever did it in the Film world, the DP wants to shoot a high contrast scenery, like from the inner car through the windshield (for example).
The DP looks to the monitor and- ohhh my goodness - you have bluish rims all around high contrast edges.
Ok, you think, poop I forgot to recall the standard lens file.
Recalled the standard lens file, everything is even worse.
You find yourself in the middle of a major shading error.

Creating a Lens File on Set?
How to make it right?
Thats my question.

I did it with quiet good success:

- Open File menu
- go to Lens File page and select a file number that has no name or offset
- name the file
- open Maintenance menu
- go to white shading
- select V MOD to on
- Aim the camera with the lens on to a absolutely flatly and even lit white card in a dark (shade) area (work with the grips and lots of black out stuff)
Try everything to gain a perfect white area.
- perform a camera white balance
- using a vectorscope, switch calibration to variable and expand until white dot in center becomes fairly large
- looking back on your White Shading menu page, you will find near the bottom a V MOD adjustment with four columns for R, G, B an M (master)
- while observing this white dot on the vectorscope, adjust V MOD:M until the white dot becomes as circular/round as possible (not oval; must be round)
- go back to the Lns File page in the File Menu
- select Store File

Dont forget, you can not store Lens Files on a Memory Stick, so the rental house is not able to send you a former lens file for your "ProblemLens" to your location, you have to create the Lens File in the Camera Body, you just can save the Lens File in the Body menus.

I found this advice in the internet on the ZGC side, it was written for remedy shading problems with the Pro35 Adapter and worked quite well for me with the T-Rex, but not absolutely perfect.
You guys have more advice for me to make this system work even more accurate?
In Munich we have now two Arri Shift and Tilt sets with Sony B4 Mounts, same thing, you need to have a proper Lens File (white shading) to get rid of the chromatic aberrations.
I think this problems will come up with every Film Lens System what is used just with a mechanical adaptor to fix the Lens on HD Camera Body, because Film Lenses are not calculated for the Prism System (3CCD) in a Video Camera.

Any further hints?

Thank you all.

Cheers,

Emanuel


Emanuel Maximilian Schwermer, bvk
1st AC - DIT - Operator
Munich-Germany
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#2 Jamie Metzger

Jamie Metzger
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Posted 20 June 2006 - 10:42 PM

Would you mind explaining what this lens file is about? I'm using this camera this week and next, and we've only had one lens, but there are so many features in this camera, that I don't think I will be able to use.
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Opal

Abel Cine

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