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HDR with film stock?


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#1 Carl Nenzen Loven

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Posted 12 November 2017 - 07:17 PM

Hey there,

I tried googling this but it seems I can not really get an answer.

The Spirit Telecine we have at my school feels a bit limited at times, and the grader knows we can not get the full potential of film. I was wondering if there would be a way to do two separate scans, and later connect them together in the grading process?

I know I will not get the full effect of something that was shot HDRx, but first I want to get all thats possible out of film.

Also, if this process work, would it be possible to tailor it to be screened for Dolby Vision and still achieve a somewhat HDR-video coverage?

Clearly I am a novice, but I am here to learn...

C


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#2 Perry Paolantonio

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Posted 13 November 2017 - 10:26 AM

Some film scanners can do this during the scan (Lasergraphics ScanStation & Director scanners, the Arriscan, Xena scanners, and for B/W only, the Scanity). They take two exposures (or more) during the scan and merge them into a composite image on output. 

 

The reason this doesn't work on the Spirit (and why the Scanity is only for B/W) is that those scanners use a line sensor to pick up the image, while the film is in constant motion. For B/W, the scanity uses one color pickup for one monochrome exposure, and another for the other monochrome exposure. It can't do it for color, because it needs to use all three RGB lines in the sensor for the primary scan. 

 

In any case, doing it in two passes would be challenging, I'd think, due to registration issues. The odds of the film being in precisely the same place during two passes seem like they'd be slim, at best. You need them to be *exactly* positioned to get it right. 

 

The Director, Arriscan and ScanStation all use area image sensors. The Director and Arriscan hold the film in the gate using registration pins (virtual or otherwise, but the film isn't moving when the exposures are made). The ScanStation takes two images *really fast* while the film is still in the gate, one for each exposure, and then it does the frame alignment in software before merging them. 

 

So, long story short, I think it'd be interesting to try on the Spirit, but I wouldn't count on it working properly. At minimum, you'd need to be able to overscan enough to see the perfs, so you can precisely align the frames in software afterwards. Using software like ImageMagick, you might be able to script the alignment and tone mapping. But it's going to be tricky and may require more effort than its worth.

 

-perry


Edited by Perry Paolantonio, 13 November 2017 - 10:29 AM.

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#3 Michael Rodin

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Posted 13 November 2017 - 10:51 AM

I know I will not get the full effect of something that was shot HDRx, but first I want to get all thats possible out of film.

Actually a HDR scan of Vision 3 will have much, much more overexposure latitude than HDRx RAW.


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#4 Chris Burke

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Posted 13 November 2017 - 12:23 PM

As the previous post stated, if you are shooting vision3 stock you do not need a high dynamic range scan. Spirit will get all the information off of the negative. Maybe the one that you our school needs a tune-up but modern-day stock and the spirit datacine go hand-in-hand very well.
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#5 Robin Phillips

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Posted 13 November 2017 - 07:12 PM

Just wondering are you at Chapman? if so, glad to hear the old datacine is still in use. IIRC they were primarily intended for HD work and dalies pipelines, but I don't think there is anything stopping you from doing a rec2020 / DCI scan with one.

 

oddly, the wikipedia entry on the spirit series of scanners/telecine devices is fairly comprehensive as a crash course into the system https://en.wikipedia...Spirit_DataCine

 

This probably isnt that helpful, but I've seen some spectacular scans off spirit 4ks in the past, though they were rec709 finishes (Fruitvale station was Spirit->HDcamSR, ol fotokem just wont let tape die). The operator should be able to give you a flat image with which you can unfold more latitude ala SLOG or a similar container. I've seen stuff off scanstations and goldeneyes done this way, so I'd imagine you can do it with a spirit.

 

If the scanner has a keycode reader, consider sending a pull list to a lab that has one of the fancier "HDR" scanners (theres a bunch on the forum). it'll will cost, but if you want a triple flash scan thats the best way to really play with how far you can take film. My colorist was floored when he got a look at stuff we got back that went through cinelab's Xena scanner. And man, if you can use a director 10k like they have at Roundabout... your mind will be blown


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#6 Robert Houllahan

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Posted 13 November 2017 - 11:15 PM

A SDC2000 classic Spirit is somewhat limited by it's undersampled CCD imager array which only scans in full 1080 line with a B&W CCD and then has three color CCDs which are 1/2 lines.

 

That said Walking Dead is scanned and finished on an older Spirit.

 

The new Spirit like our Spirit-2K at Cinelab has three 2K/4K Linear CCDs at 16bits and has excellent DR (much more than a single flash Scan Station and possibly more than an HDR one in Data Mode.

 

Xena, Direcor etc use area array monochrome CCDs and can do multi flash exposures for HDR.

 

The new HDR option on Scan Station seems great (We have not upgraded ours to a full machine yet) as it still retains high speed (15fps) but I am guessing the HDR mostly overcoms the 5K JAI CMOS cameras fixed pattern noise issues.

 

YMMV

 

Rob


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