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Mitchell Frieze 35R5 and CGI


Chris Cushley

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Hi I am an cgi artists and am working on a job with moco data. The footage was shot with a Mitchell Frieze 35R5 and the data has alot of offsets. I have worked with moco before and never had so many problems. Usually I match my cgi camera to the film back as shot then crop my render output to match the transfer. In this case 1.33 full ap to HD1080 place in my offsets based on data I collected on set and bingo I am done. In this case it's not working. Initially I thought there was a slight offset in the tilt of the camera but after carefully watching what was happening and playing with my offsets I realized it's a problem with the film back.

 

My software if set to full ap 1.33 gives me a horizontal apurture of .980 and a vertical of .735

 

Although I can't find much info on this camera in researching I found mention that the super TV lens used on these cameras is listed as either 2.55 or 1.85. If I set my film back to my software default 1.85 (horizontal .825 vertical .446) I am much closer but still off. I also tried setting my film back to software default 35mm TV projection 1.33 (.816 horiz .612 vert) Again this is much closer than full ap 1.33 but still not right.

 

I was hoping someone could give me some insight as I am more confused now than when I started. I have contacted the person who rented the camera and asked for micrometer readings from the film gate but so far have got nothing.

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This is hardly my area of expertise but -- I'm puzzled by "Super TV lens" I mean either a lens will cover Super TV of it won't.

 

 

Anyway, why not contact Fries Engineering directly (note spelling) , maybe they'll have some answers. At least they'd know what the aperature size is on the camera they assembled !

 

-Sam

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appriciate any input. First people I tried to contact was fries and am still waiting to hear back from them.

The only info I was able to get from the dp was it was shot full app with an academy masked framed for 1.78HD1080 and they used a "super tv lens".

 

The person who owns the camera is simply not returning any calls. It's a heart breaker really. manually tracking this is not going to be fun.

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Still don't understand what the lens has to do with it. "Super TV" is a quasi-format that evolved a few years ago where the entire silent aperature film area is used, as opposed to the smaller offset Academy aperature. Both are 1.33 frame ratio.

 

Lenses do not have a frame ratio. Either they are spherical or they are anamorphic to sqeeze an image that is larger in horizontal length. The most common anamorphic for 35mm is a 2x squeeze, which is generally used to produce a 2.35 frame (discarding some of the sides). There are also 1.5x and 1.33x anamorphics, but they are either outdated technology or for video formats.

 

One possibility is that the lens cannot fully cover the full 1.33 Super-TV format so the corners would go dark, but it is possible to extract a 1.85 or 2.35 frame. The problem again rises that Super-TV is not a precise framing system and their is no true set standard for this that you can align to. If they were shooting with a lens that did not fully cover but planned on extracting a 1.33 image from a slightly smaller area, then it's a big guess as to what that area may in fact be. This is where framing charts become so important, as they could have simply photographed one for all the post facilities to align themselves to. An AC in LA named Mako makes an excellent chart for Super-TV shooting for this very purpose.

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It seems you really need to know the focal length of the lens rather than the aspect ratio. If the 3D software is using a different virtual lens to what the real footage was shot through, any camera movement will give away the 3D elements through mismatched perspective and object movement.

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The more I learn about this the odder the set-up (as reported back to be seems),

from what I can tell shooting full app with an academy mask for hd1080 framing with a superTV lens is not a very standard approach. The focal length is 24mm but the problem is I get drastically different effects depending on the filmback I set to. Usually I am told we shot a 24mm lens full app. I set my lens to 24mm, I set my film back to full app and I am done.

 

I've now spoken to 2 guys at fries engineering and they are also a bit confused, apparently there is one guy there who can help but he's (of course) out of town.

 

It's definately a puzzle but the more I learn the more appriciation I get for DP's and all they need to deal with.

 

I really appriciate everyone who has taken the time to drop there insight here. Many thanks.

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