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Telecine color charts and images?


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#1 Otis Grapsas

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Posted 20 January 2007 - 06:45 AM

Hello, this is my first post:)

I'm a software engineer and I'm developing a low cost uncompressed digital cinematography solution for low budget/no budget filmmaking. I have experimented with various CMOS and CCD sensors on the market and decided after testing and measurements that CMOS is incapable of good quality due to poor low light performance, extra processing needed to cover pixel faults, pattern noise and motion quality problems inherent in the technology. On the other hand, CCD is capable of good saturation and signal per noise performance in average light, very linear in low light (good shadow detail), capable of preserving saturation in low light and very sensitive. Even the noise quality is better when the image is recorde uncompressed due to its statistical qualities. The only drawbacks compared to CMOS are a lower MTF which results in softer image with equivalent pixel count, smear problems which are not a big problem in quality CCD, and split pattern effects on the large pixel counts which can be solved to a degree by properly controling the amplifiers.

I'm at the point where I need to decide on the color response of the system and implement color correction algorithms. It is easy to get technical precision using a color chart but I'm more interested in the nonlinearity of film and its saturation properties. I have no access to cine film equipment or quality telecine.

1) I have read the documentation of Kodak cine stock and compared to normal SLR film. The measurements look quite similar. Is this true? Or is there something special about cine film that is not immediately apparent on the film specifications? I'm talking about the properties of the original negative processed film, not about differences in the final projected image from further processing and generations required for interpositive/negative and distribution. Will tests using SLRs be good enough for my purpose? What type of stock should I choose? I have access to a good photo lab that will not autopilot and "enhance" the scanned output.

2) I have read various articles on the properties of cine film, especially on the behaviour in daylight and various degrees of low light. But nothing with actual images that can quantify these properties. Is there any source on the web for tests charts digitized with good quality in the typical light situations?

3) What does a filmmaker expect in terms of color quality from his 16 and 35mm film when he gets the digital material from the lab? This is the quality I want to emulate. Any test or normal frames including skin tones, sky, sea, trees etc would be most helpful in tuning tthe response of my design. Material that went through simple generic timing would be a lot more helpful than creative color correction. Color charts would be ideal.

Any help would be greatly appreciated. Sorry about my english.

Thanks.
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#2 David Mullen ASC

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Posted 20 January 2007 - 12:04 PM

35mm still camera color negative film is similar to motion picture color negative. I find that motion picture color negative is a little lower in contrast though. The 35mm movie format is also half the size of the still camera format (4-perf instead of 8-perf) and the stocks used are often tungsten-balanced instead of daylight-balanced. The perfs are a little different and some other mechanical differences (like the rem-jet backing on motion picture stock to reduce static problems, etc.)

But for ballpark testing, 35mm still camera film will work for awhile as long as you factor in that motion picture film has a little more exposure latitude.
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#3 Otis Grapsas

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Posted 20 January 2007 - 04:49 PM

So, the cine negative has more latitude, but after the generations required for final output I guess it should be pretty similar. Every step should increase contrast.

Latitude is not a problem with the sensors I'm using. It is similar to the crop factor DSLRs because the pixel area is equal or larger. I have also lots of flexibility because the signal is 16bit from a 14bit AD. In 8bit formats I would need very drastic curves to fit some latitude to the format. This has to be done later on to produce the common formats, but there is some room in post before final output at least.
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