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Marta Teixeira P. Simoes

Overexposure or bad telecine?

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Hello, 

I just got the results of a telecine from a project shot on S16 and we've noticed a strange behaviour in some of the shots, specially whenever there's a sky with clouds.

I'm not sure if you can spot in the images attached (the detail of the sky is a zoom in on the still), but there's vertical lines all over the sky.

The lab says it's because the footage was overexposed, but still I find it very weird that this would result from an overexposure error. When I see it in movement it reminds me more of "digital" noise than film behaviour.

This is a rough translation of what they wrote:

"It is true that the artifacts come from the ccd cell of the TC.
When the negative is overexposed less light passes through the cell.
The negative is thicker.
And I must increase the "gain" or iso, when I lower the ISO the high light burns.
I sent two more tests with a lower ISO."

I'm also attaching the other two tests they mentioned, which are completely overexposed.

It could be that I did make a mistake and overexposed, but I have two doubts - if it was that bad, could they recover that much information from the sky (like in the image1 attached)? And these strange lines could indeed be a consequence of that?

The post production supervisor says we should not trust the lab’s answer, and they are doing the telecine wrong in order to push us to scan. Apparently he has had this feeling before with other projects, but I would great to have another experienced view on this.


Thanks!

image1.jpg

image1 detail.jpg

image 2.jpg

image 3.jpg

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I have had this issue once, surprised me as well. I didn't think I had overexposed that much. Anyway, I don't believe there was any deceit going on - but would be nice hear from others who have faced this same issue. No other lab has ever returned me footage like that. Have those labs just clipped the highlights without asking or is the tc equipment so different?

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It’s normal to have noisy highlights from a telecine if the negative is very dense. The telecine will have an older digital sensor - when the negative is too dense, it underexposes the sensor.

Some DPs will avoid overexposing the negative if they know they are going straight to telecine or scan and not printing. For printing, you would usually want to overexpose a bit to get a less grainy image. 

A film scan will have less highlight noise, especially if you use a machine that can take multiple exposures to capture both highlights and shadows separately. Also, their digital sensors will be more modern and have more dynamic range.
 

 

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Depends on the scanner and or telecine and also how it is setup.

These kinds of artifacts are from FPN (fixed pattern noise) in the sensor and show up in dense negative typically.

The hilites are the densest part of the negative and they translate to the shadow area of the sensors response. Think about black shading a RED camera for example. So if there are noise issues in the sensor that is where they will show in the negative scan, and that is why film scanners need very high quality sensors with low noise.

A BMD Cintel with its 4K cmos sensor or a Scan Station with the 5K CMOS sensor will easily show this and even worse vertical lines throughout the dense parts of the negative. The new 6.5K sensor used in the Xena and Scan Station basically eliminates this problem.

A "Classic" SDC2000 series Spirit will show this much more than the newer 2K/4K series will. And any Spirit which is run without doing a FPN calibration and light intensity adjustment for the density can show FPN noise as above.

On my Spirit 2K (Setup as 1080P HD out with the scaler boards) I can make 1080P REC709 scans without showing FPN and noise in extremely dense negative, that is a 2008 built Spirit. Older Classic spirits will have a tougher time, as will many Cintel CRT telecine.

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I looked at this same negative again just this afternoon. There is a 3.5 stop overexposure compared to the shot before and after. The printing lights are at about 45 for green. The rest of the shots is around 25 for green.

I could have it scanned on an Arriscan to see how it will come out. 

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