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#1 Ed Davor

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Posted 30 August 2014 - 04:57 PM

Hi

 

Recently I saw this documentary on youtube that showed the actual process of creating one of the scenes from Return of the Jedi. They showed a person operating an optical printer. But there is something I didn't quite understand about the process. Please take a look at this clip and I'll explain what I don't understand:

 

 

Around 4:55 you can see the optical printer superimposing the mask and the foreground footage. Before the mask aligns you can see the blue screen. I thought that negatives are composited together in the optical printer. If you can clearly see the blue color, this can only be a print. Either that or they adjusted the colors in this video so you can see the actual image (but I doubt it, since this documentary was also shot on film).

 

Also take a look at 2:50.

 

The person is creating a matte box for this shot with cards. I remember a couple of instances in SW (in older video transfers) where you can actually see this box around the ships (the black changes it's level in that area). But what is this person putting the cards in front of? Is it a screen of some sort? Is this rephotographed from a rear projected screen or something? It can't be some kind of a gate because it's too big. And again, the image behind is clearly a print. Did they copy prints unto a new piece of negative stock? Wouldn't that cause gamma issues?

 

If it's true that they used prints in optical printers, why is that? Wouldn't it be better to compose low gamma negatives unto a fresh piece of intermediate stock (gamma 1?) in order to preserve the contrast? I don't get the gamma math here.

 

 

 


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#2 David Mullen ASC

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Posted 30 August 2014 - 05:14 PM

The idea is to create a final composited image as a negative so that it can be intercut with the live-action non-efx negative.  

 

Since it's generally a negative-to-positive process (unless you use reversal stocks, which the original "Star Wars" did for light sabers and laser bolts using CRI stock, all of which had to be redone in the restoration because it turned out that CRI stock had poor archivability) you would load a positive made off the original negative into the projector side of the optical printer and rephotograph this onto negative stock in the camera side of the optical printer.

 

The positive element if color would usually be a low-gamma interpositive made onto intermediate dupe stock, not a normal/high gamma projection print.

 

The person making the garbage mattes is using an animation stand and a projected frame from a print as a guide, the projected image isn't going to be rephotographed, they'll just take a photo of the black mattes against a white field and create a hi-con b&w positive from that.  When sandwiched with the hi-con b&w hold-mattes created from the blue screen material, the lights and stands can be masked out to create a final hold-out matte that just contains the outline of the object to be composited over another element.

 

Variations in the gamma of the b&w hold-out mattes are generally not visible in the final projection print, but can be visible in later video transfers made from lower-contrast film elements unless the blacks are crushed.  Aging of the film elements probably also exaggerate the difference in blacks.  Also, ILM tended to use less contrasty hold-out mattes to allow some bleed-through of fast moving objects over the background plates so that they wouldn't look like cut-outs but had some natural transparency from blurring past the camera.


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#3 Ed Davor

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Posted 30 August 2014 - 05:41 PM

Thanks for your answer David,

 

One thing that puzzles me is that they show a vistavision print in there too. So I thought that this was the same piece of film they put into the printer. So you are saying that it's an IP that goes into the printer instead. I've never actually seen one; does it have a cyan tint, or is the orange mask at this stage fully compensated?

 

In this documentary there is one instance where they actually do use a print; it's for the ewoks dance scene where they project a print onto a piece of screen behind the matte painting on glass and photograph it then together. But it's a small image area so I guess the contrast issues weren't noticable so much.


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#4 David Mullen ASC

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Posted 30 August 2014 - 06:12 PM

Ideally you'd use as few generations as possible so if the original element was shot in spherical 8-perf VistaVision on camera negative stock, then the I.P. would be contact-printed and thus also 8-perf spherical but was rephotographed thru an anamorphic lens onto 4-perf 35mm dupe negative stock while it was being composited with other VistaVision positive elements, so that the final dupe negative could be cut into the live-action negative which was 4-perf 35mm anamorphic in the case of the original trilogy.

But sometimes it wasn't possible to do things without further generations. For example Doug Trumbull's EEG company that did "Close Encounters", "Star Trek: The Motion Picture" and "Blade Runner" did not have a 65mm-to-35mm optical printer so they did all of their effects in 65mm and composited them onto a 65mm dupe negative, and then sent that out to be reduced to a 35mm dupe negative (I don't know if from a 65mm or 35mm interpositive). It's a testament to the high quality of 65mm that the effects survived so many dupes (and Trumbull used lots of tricks to find ways of skipping generations, like photographing matte paintings onto 65mm dupe intermediate stock). Plus it had the unexpected benefit decades later of allowing the 4K digital restoration of "Blade Runner" to use the finished 65mm effects rather than the 35mm copies of them.
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#5 David Mullen ASC

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Posted 30 August 2014 - 06:18 PM

An I.P. has an orange color mask just like camera negative.

Though sometimes effects elements were converted to three b&w color separations (YCM's) to improve image quality, at least until Kodak started making better color dupe stock. The optical printer composites in "2001" used 65mm YCM's to retain as much quality as possible (when the effects couldn't be done with double exposures or animation stands.)
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#6 Ed Davor

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Posted 30 August 2014 - 06:32 PM

Thanks,

 

So if the IP has an orange mask, does that mean that the color bias from the negative is compensated to neutrality? (orange in the neg is blueish-cyan when reversed, yet compensated by more orange in the IP?) In other words. If I were to look at the image on the IP, would it look like a neutral low con print? Or would the image be blueish?

 

That piece of film that they are watching on the lighttable in the video, is that a print or an IP? Judging by the clear base I'd say a print, right?


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#7 David Mullen ASC

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Posted 30 August 2014 - 09:00 PM

The color mask isn't designed to add more orange to the interpositive image, it's just a way of creating more accurate color response The image on an interpositive is low contrast and has somewhat odd colors plus has that orange mask.

You'd use a work print in the animation stand as a guide for rotoscoping or making garbage mattes or doing animation like laser bolts. Could also be a b&w print.

http://photo.net/lea...e-negative-mask
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#8 Ed Davor

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Posted 31 August 2014 - 05:19 AM

I know the orange mask in the IP isn't made to compensate for the blueish cast (but to tweak the IPs colorimetry), but in theory at least, it still does add more orange to the image I guess.

 

Thanks


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#9 cole t parzenn

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Posted 31 August 2014 - 11:32 AM

Was Trumbull the only one using 65 and Dykstra the only one using reverse bluescreen? Also, were the "2001" models shot against blackscreen, with hand-drawn mattes? That'd be the best way to do it, I suppose.


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#10 Mark Dunn

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Posted 31 August 2014 - 12:03 PM

 Also, were the "2001" models shot against blackscreen, with hand-drawn mattes? That'd be the best way to do it, I suppose.

Yes. All the 2001 composites were rotoscoped by hand. There were no travelling mattes.


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#11 David Mullen ASC

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Posted 31 August 2014 - 04:11 PM

In terms of rotoscoping being the best way to generate a matte, it's not necessarily a "better" way, just in the case of "2001", a black matte line around the spaceship wasn't going to be visible against a black background with stars -- and besides, the model was 54' long!  A blue screen would have been difficult to work with at that size and blue spill would have been a problem with such high-contrast lighting with deep shadows.  This is one reason Douglas Trumbull did a white screen / silhouette technique for the Enterprise model in "Star Trek: The Motion Picture" (the shiny paint job made it difficult to pull a key from, especially with blue screen), but that technique is only possible with motion control since it involves matching multiple camera moves.  "2001" used a primitive version of motion control in order to move the camera at extremely slow speeds for the very low frame rates involved, but they did not attempt to do multiple passes.


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#12 David Mullen ASC

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Posted 31 August 2014 - 04:16 PM

Trumbull used 65mm more extensively than any other effects houses but other companies used it at times, for example, Tom Howard, who developed the front projection technique used in "2001" involving 8x10 slide projection developed a 65mm front projection system used in some movies of the 1970's (maybe "Battle of Britain", I don't recall.)  After "Star Wars" re-introduced the VistaVision format for effects work, a number of other companies started using VistaVision as well.

 

I don't recall other companies besides Dykstra's using the UV "reverse" blue screen technique.


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