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Double DI scans and fill light.


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#1 Paul Bruening

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Posted 16 February 2008 - 11:45 PM

Hello good folks,

As we all know, sunlight can be harsh. We are often obliged to fill in shadows with as much as three and a half stops worth of light on the hot end of the lens aperture. That means a hell of a lot of light either electric or reflected sun.

Has anyone tried to get bracketed exposures at the DI scan stage and then macro them back together in post to take advantage of films inherent exposure latitude? Am I making sense? Normally expose the negative, then normally expose the digital image of the negative, then overexpose another digital image of the negative to get higher detail of the shadows, then chop out the darks from the normal digital and chop out the highs from the overexposed digital image, then composite them together so that you get the normal highs but the lightened-up darks from the other digital image. If the math in the compositing was right, you might not see the joins. Think of it... no more fill light on daylight exteriors.

Has this already been done? I had originally thought of it in terms of getting two 2-perf images top and bottom through a pellicle and mirror splitter with an ND9 on one of the images, then compositing them back together in post.
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#2 David Mullen ASC

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Posted 16 February 2008 - 11:57 PM

A scan of a 35mm negative is already supposed to contain all the luminence information on the negative, compressed into a 10-bit LOG form. The only way to get more information is to shoot separate exposure passes in the camera and combine the two images in post, but then you have all sorts of problems shooting simultaneous images of the same thing but at two different exposures. You'd need an over-under 2-camera rig, or a beam-splitter inside a camera to send a picture to two different frames, one image having passed through an ND filter on the prism block.

Besides, aren't some people already complaining that modern color negative has too much latitude? The hard part is getting the shadows to go black; getting them to pick up detail isn't so hard.

It's really the digital cameras that may benefit from some HDR technique until their latitude improves.
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#3 Chris Keth

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Posted 17 February 2008 - 01:23 AM

It's really the digital cameras that may benefit from some HDR technique until their latitude improves.


That begs the question: Could one design a digital movie camera with great latitude simply by splitting the light onto two sensors, one of them with ND so that two records are recorded simultaneously with different exposures.
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#4 Saul Rodgar

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Posted 17 February 2008 - 01:47 AM

Hello good folks,

As we all know, sunlight can be harsh. We are often obliged to fill in shadows with as much as three and a half stops worth of light on the hot end of the lens aperture. That means a hell of a lot of light either electric or reflected sun.

Has anyone tried to get bracketed exposures at the DI scan stage and then macro them back together in post to take advantage of films inherent exposure latitude? Am I making sense? Normally expose the negative, then normally expose the digital image of the negative, then overexpose another digital image of the negative to get higher detail of the shadows, then chop out the darks from the normal digital and chop out the highs from the overexposed digital image, then composite them together so that you get the normal highs but the lightened-up darks from the other digital image. If the math in the compositing was right, you might not see the joins. Think of it... no more fill light on daylight exteriors.

Has this already been done? I had originally thought of it in terms of getting two 2-perf images top and bottom through a pellicle and mirror splitter with an ND9 on one of the images, then compositing them back together in post.


If I understand you correctly, what you can do is HDR things in FCP or similar NLE: overlay the same footage on the timeline (stack it on top of each other); start playing with the opacity, its composite mode and image control filters to your heart's content. This technique obviously only works with digital files on a computer. That is what I have done when I feel things weren't as good as possible on telecine BUT if you transfer with a Da Vinci 2K color corrector/ power windows you can do wonders there to begin with. All you need is a good colorist. A combination of the two would work marvels. But I have never done it at scanner level or on optical printers . . .

Though David is right, with modern neg stocks you would be hard pressed NOT to get a lot of detail, even in harsh sunlight; unless something really wrong happened with your exposure, at the negative level (x-ray, heat damage) or in the soup. . . Reversal stock is a whole different thing. I have usually done what I described above when I want MORE contrast and to crush blacks on negative-shot footage, but I guess you could end up with negative that is too contrasty with some secret technique (or extreme bleanc bypass) and want to get some detail back.
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#5 Saul Rodgar

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Posted 17 February 2008 - 02:00 AM

That begs the question: Could one design a digital movie camera with great latitude simply by splitting the light onto two sensors, one of them with ND so that two records are recorded simultaneously with different exposures.


If I understand it correctly that is exactly what is avoided by acquiring on cameras such as the RAW-capture RED. I have seen some awful RED RAW files that have to be color corrected to no end no matter how it was really shot just to get something decent-looking out of them. The idea being that there is just everything there in terms of detail/ color/ latitude and one just chooses what to filter out/ tweak in post, much like negative stock scanned through a Spirit, say.

I know that is what happens when I shoot RAW pix on my DSLR. I know I will have to Photoshop it until it starts looking like the real life model/ landscape/ item I shot. It NEVER looks like it is supposed to right away.

Edited by saulie rodgar, 17 February 2008 - 02:02 AM.

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#6 David Mullen ASC

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Posted 17 February 2008 - 02:57 AM

Even in RAW mode, the RED or a DSLR won't capture as many stops of dynamic range as color negative.

There is no current prism-block beam-splitter digital movie camera that captures two exposures simultaneously. One could in theory, I suppose, take a 2/3" 3-CCD prism-block design and put three Bayer filtered sensors instead of filtered monochrome sensors, and put different ND's strengths on two of the three sensors to get different exposures.

But for 35mm-sized sensors like the RED, a prism block (just as with an old 3-strip Technicolor camera) would limit the types of lenses one could use due to the flange depth. Not to mention the size and weight of the camera would increase.

The Genesis has a single RGB striped sensor and each color row has two stripes, one ND gelled to capture more highlight information. Hence why 12MP is needed just to end up with 2MP per final color record (HD resolution.)
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#7 John Brawley

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Posted 17 February 2008 - 05:28 AM

Hello good folks,


Has anyone tried to get bracketed exposures at the DI scan stage and then macro them back together in post to take advantage of films inherent exposure latitude? Am I making sense?



Yes you are.

Arri already do this on their Arriscanner. It's a great machine and I have done several jobs with it now. It's has a mode where it does 2 scans, and combines them to then generate the final scanned image.

I was very impressed with it, and it's better than the imagica scans I've done on other jobs. Im about to do my first northlight scan so we'll soon see how it stacks up.

I think the arri wins even if the northlight's reputed slight edge in resolution proves to be true. The arri scans at up to 12 FPS, vs 1FPS with the northlight.

You do have to ask for it through, because of course, it takes twice as long ! Not something every post house would be excited about.

have a look at

http://www.arri.com/...AN_Brochure.pdf

jb
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#8 Saul Rodgar

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Posted 17 February 2008 - 11:30 AM

Not something every post house would be excited about.
jb


Unless they are charging a flat rate for transfering vs the hourly rate standard in the US, they would be excited, since the longer it takes to finish the job the more money they collect! :P With the exception that their scheduling is tight I can't see how they wouldn't want people to spend more money by staying longer in the transfering suite.

Haven't transfered on an Arriscan. Looking forward to . . . The place I use has a Spirit scanner with DaVinci 2K, charges half the going rate and does a great job; which is good enough for me right now so until producers startdropping the big bucks, I'll probably stick to that for a while . . .
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#9 David Mullen ASC

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Posted 17 February 2008 - 11:56 AM

I don't believe the "dual scan" mode of the Arriscanner is to increase dynamic range, it's to increase the resolution of the scan -- the sensor is essentially the same one in the Arri D20 camera, nearly 3K, so by doing a half-pixel offset in the second scan, they can get higher resolutions.
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#10 John Brawley

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Posted 17 February 2008 - 06:11 PM

I don't believe the "dual scan" mode of the Arriscanner is to increase dynamic range, it's to increase the resolution of the scan -- the sensor is essentially the same one in the Arri D20 camera, nearly 3K, so by doing a half-pixel offset in the second scan, they can get higher resolutions.



Hi David.

It does have a mode for increased dynamic range, but I could have phrased it better. It has a dual flash mode, where the light source flashes at a low power and high power mode to give extended dynamic range.

It *ALSO* has a dual scan mode for higher resolutions. In fact, it scans 4 times !

So the sensor can scan multiple times on the same frame and it can have two passes of exposure.

So it has a 3k Sensor. You can choose to get 4K, 2K or HD from it native, with one or two flash exposure.

Or you can use it in 6K mode, where it does 4 scans (with half pixel offsets) and that can be done in either two or single flash exposure as well.

I should add, that arri argue that it's a true 6k resolution, because the ACTUAL sensor moves half a pixel in all directions when scanning this way, rather than doing it electronically.

All these permutations also affect the scanning time of course as well.

jb

Edited by John Brawley, 17 February 2008 - 06:13 PM.

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#11 Paul Bruening

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Posted 18 February 2008 - 02:08 PM

This is all good news. Yet, I still am interested in if this allows the DP to shoot without all that fill light gear. I'm asking as a no-budg producer. Can I fire the lighting crew and shoot an entire movie in daylight exteriors with only a camera and sound crew? No gaffers, no generators, no miles of cable, no electricians, no trucks, no drivers, yadda yadda yadda. Just three guys on cam and two guys on sound. No accounting staff to keep up with a hundred guy's payroll. No craft services with a mountain of food to pay for.

Can dual scan do this? If not, can split, dual techniscope exposure on a 4-perf pull-down frame do this?
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#12 David Mullen ASC

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Posted 18 February 2008 - 02:49 PM

The problem with film, the need for lighting, etc. goes way, way, way beyond providing fill outdoors, which is one of the easiest things to provide, if even necessary these days with modern stocks. And I don't really think this "dual-scan" system provides more shadow detail anyway. Like I said, a 10-bit LOG scan is normally supposed to contain all the information on the film anyway, so there is no "hidden" shadow detail -- the scans are very flat and milky and generally you are adding contrast to them.

You can shoot a film outdoors without fill right now if you wanted to (look at Terrance Malick movies), but even if you needed fill, what's so hard about holding a white card?

This is basically a non-issue in terms of reducing costs of production, the need to provide fill light outside. If you can't even afford a white card or a bounce frame, then your production has much bigger problems.

The reason you need big lights or big frames outside in daytime is mainly due to continuity -- matching one shot made in sun to another made in overcast, or removing harsh sunlight when it's unattractive while making it consistent, etc.

If you want to hike into the mountains with just a film camera, you can do that now with current stocks and post methods.
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#13 John Brawley

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Posted 18 February 2008 - 03:39 PM

This is all good news. Yet, I still am interested in if this allows the DP to shoot without all that fill light gear. I'm asking as a no-budg producer. Can I fire the lighting crew and shoot an entire movie in daylight exteriors with only a camera and sound crew?



You know, you can fire them right now without having to use a dual scan or beam splitter. You'll get a picture. But it probably won't look any good.

Are you kidding ? Who's going to rig the camera to a car safely for you ? How are you going to do any tracking shots ?

I think this a very simplistic way of looking at the process and as a producer, you should be more concerned about getting the best results rather than simple economics which are based on a false assumption.

Even if you could do this kind of imaging, the reason the electrics are there is to give you a consistent result, and for a creative outcome. As the sun moves through the day and goes in and out of clouds, you want to be able to maintain some consistency. If you had to spend time in the grade balancing the shadows from shot to shot ( and i don't think it can be done the way you want to ) you'll spend a lot more money in post than firing the electrics.

jb
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#14 Leo Anthony Vale

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Posted 18 February 2008 - 03:59 PM



It does have a mode for increased dynamic range, but I could have phrased it better. It has a dual flash mode, where the light source flashes at a low power and high power mode to give extended dynamic range.


I thought this was for scanning prints or reversal originals, since their density range is greater than a negative's.
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#15 David Mullen ASC

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Posted 18 February 2008 - 04:09 PM

John mentioned to me that he saw some improvements from the dual scan mode in terms of noise.

I can see the advantage in the sense you can have one scan biased towards the highlights and the other towards the shadows for optimal noise throughout, so lifting the gammas in either direction would look cleaner than it normally does, allowing greater flexibility in color-correction. So I don't think of it so much as a big increase in dynamic range so much as an increase in color-correction latitude in dealing with high contrast images.
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#16 Paul Bruening

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Posted 21 February 2008 - 12:11 PM

Hey David,

Yea, that's about all I really had in mind- reduce contrast. It occurred to me that the darks on the shade side of an object, especially humans and their faces, can be too dark. Of course, that's why everyone uses fill light. As well, scenes in cars or scenes in large shadows like buildings that include sunlit objects or scapes in-frame can be an extraordinary nuisance to compensate for. It just seemed like it would be darn handy to use a trick in post to make life during shooting a little easier. If this technique gave useful results, productions like westerns could really benefit. Of course, I do know this could reduce employment of precisely the people who read this forum. At the same time, there a plenty of producers at my level (completely broke) who might find some value in this technique.

It was just an idea.
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#17 David Mullen ASC

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Posted 21 February 2008 - 12:18 PM

Hey David,

Yea, that's about all I really had in mind- reduce contrast. It occurred to me that the darks on the shade side of an object, especially humans and their faces, can be too dark. Of course, that's why everyone uses fill light.


It's not as mechanical as that -- not everyone uses fill light even when it's sunny.

Besides, it's not really cost effective to think that a dual-scan on an Arriscanner is somehow cheaper than a bounce card.
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#18 K Borowski

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Posted 22 February 2008 - 12:08 AM

Besides, it's not really cost effective to think that a dual-scan on an Arriscanner is somehow cheaper than a bounce card.


Exactly. Taking the trouble and expense to shoot one's personal project on film, and then not adequately light makes no sense to me. Sure, you can do some pretty impressive work fixing footage that hasn't been exposed correctly on neg film, but that will almost never look as good as properly exposed footage, and will take more time and cost more.

That being said, I certainly hope that this sort of scanning technology becomes more widespread and quicker with newer scanners, because there's some great potential here to do HDR-esque effects using this sort of scan in addition to what David Mullen says about reducing noise as you get into the toe and shoulder of the curve trying to pull out detail. There's a lot of information that is getting left behind on the negative, and if DI can pull more detail out of a negative through this sort of scanning it would tip the scales in favor of DI for me. At present, most DIs I have seen have been lacking compared to a photochemical finish.
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