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Your DREAM SPECS for a Digital Cinema Camera?


Tom Lowe

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Foveon always has been a CMOS process from what I understand.

I swore the first model was a CCD. **scrambles to look it up**

You're right, it has always been CMOS. Incidentally, they do sell the units to third parties, so anyone wanna team up in using one paired to a 4:3 lens mount? 8)

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If we're going to dream, then, let's dream! I'd like a device that could record my imagination. Yea, what I see in my head. I would prefer it if it could store the data in such a way that it could be edited, then, played back in the viewer's head, directly. I assume distribution would work itself out much like videos do on Youtube. I'd call it, Occipitovision.

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If we're going to dream, then, let's dream! I'd like a device that could record my imagination. Yea, what I see in my head. I would prefer it if it could store the data in such a way that it could be edited, then, played back in the viewer's head, directly. I assume distribution would work itself out much like videos do on Youtube. I'd call it, Occipitovision.

Brainstorm...

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???

 

You cannot "apply" foveon to an existing sensor. It is a new structure of the CCD so I understand, enabling each pixel to record each color, rather than interpolating as through a beyers pattern. But yes, as of yet the largest foveon would rate as only 2k.

The principle of the foveon is simply that red light penetrates further into silicon than blue light, so if three very thin photocells are stacked on top of each other, the deepest one will only record the Red part of the image, the middle one will record both Red and Green, and the top will record Red, Green and Blue. Subtracting the deepest (Red only) signal from the middle (Red + Green) will give the Green signal, and subtracting the middle (Red + Green) from the top (Red+Green+Blue), will give the Blue signal.

Because the three photocells are on top of each other, in theory you can get triple the pixel density and there are no compromises about offset pixels.

 

In practice, the high density construction tends to reduce the signal-to-noise ratio to the point where the chips do not really work much better than simple having RGB filtering on three times as many photosites. You also have no control over the spectral response of the silicon "filters", and so the post-processing circuitry has a lot more work to do. The upshot is that in practice, their performance is little better than a simple Bayer mask.

 

In theory, they should be capable of better results, but any improvements in silicon technology that make them more practical, will probably make conventional sensors even more practical.

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SNR can work out good for luma though - you just sum the top, middle and lower responses. However chroma is suspect, especially after the very strong color correction matrix that is needed to get RGB out. Extensive chroma noise reduction is part of the basic raw decode pathway (see Foveon docs for more info). Keith, as you point out, silicon just isn't a very good color filter. However, the end result is a clever and unique technology, but, at the resolutions we'd want to use, way too slow for digital cinema use.

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In theory, they should be capable of better results, but any improvements in silicon technology that make them more practical, will probably make conventional sensors even more practical.

Maybe -- but what if they come up with a way of making color filter layers within the silicon, between the stacked photosites? That would sure improve Foveon's channel separation.

 

 

 

-- J.S.

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First of all you do not need to be a billionaire to come up with specifications that will outperform a Red camera even at no additional cost. All you need is creativity and brain power. That being said what the movie goer wants is the IMAX experience with the gigantic screen. However when the screen becomes so big that it occupies the periphery of the human visual system why is it that you have to maintain a constant resolution since no one looks out of the corner of their eye. What we need is a space variant resolution that concentrates the resolution more towards the fovea of the visual system and generates less resolution towards the peripheral areas of the human visual system.

 

The trouble with this is: when I see an IMAX feature one of the fun things to do is to let your eyes rove all over the screen, even in the corners, to pick out tiny, interesting details. That's the beauty of IMAX.

 

Resolution really is not a problem for the future. Resolution will continue to increase and increase and increase...

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The trouble with this is: when I see an IMAX feature one of the fun things to do is to let your eyes rove all over the screen, even in the corners, to pick out tiny, interesting details. That's the beauty of IMAX.

That's exactly my problem with IMAX for narrative cinema: there is no composition. The camera just points at the action, but you cannot really play with off screen/on screen which is an essential tool for storytelling.

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That's exactly my problem with IMAX for narrative cinema: there is no composition. The camera just points at the action, but you cannot really play with off screen/on screen which is an essential tool for storytelling.

 

How is IMAX any different than 35mm, other than aspect ratio? Certainly, if you were shooting a narrative feature in the IMAX format you could crop the thing to a more cinematic ratio. In terms of composition, DOF and framing could be used to draw or direct the viewer's eye on that large screen.

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In terms of composition, DOF and framing could be used to draw or direct the viewer's eye on that large screen.

Hmmm .... You'd have to think a little differently about it, given that it's supposed to occupy a larger angle of view for the audience. For instance, a choker closeup that works OK on TV can look pretentious and silly on a big theater screen, and probably even worse in IMAX. So, you'd want to play everything wider. Maybe even use the sets rather than frame lines to define spaces, with people making entrances and exits almost like a live stage production?

 

 

 

 

-- J.S.

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Maybe -- but what if they come up with a way of making color filter layers within the silicon, between the stacked photosites? That would sure improve Foveon's channel separation.

-- J.S.

I doubt that would ever be practical. Most silicon chips these days are manufactured by "painting" new layers of silicon onto a pre-existing silicon substrate, by decomposing ultra-pure silicon tetrachloride gas. To produce the desired electronic properties, the layers of silicon have to be deposited as perfect crystals, and the only known way of doing that is to lay them down on a pre-existing perfectly crystalline surface.

 

If you put any kind of filter material in between the substrate and the grown layer, the grown layer would be deposited like a layer of polycrystalline "frost", rather than the layer of monocrystalline "ice" that is required. Polycrystalline silicon ("poly") is fine for making electrical connections, but it it performs very poorly for electronic functions.

 

In any case, no matter what chemical substance was used for the filtering, it would eventually contaminate the silicon layers.

 

Apart from that, the sensor layers in a Foveon are extremely thin, as light of any wavelength only penetrates slightly into silicon. A dye filter would have to be much thicker and so the light would tend to spread out considerably by the time it reached the red sensor. The dye layers would probably not provide the physical support needed for the ultra-fragile silicon layers either.

 

If we want to get into Science Fiction, what about a combination of LCD and a conventional CMOS or CCD single chip sensor. The incoming image could pass through the LCD device, which would be able to automatically vary its density in brighter areas so as to flatten highlights, giving a more film-like result.

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Call me overly-simplistic and archaic, but personally, for my needs, I would be super satisfied for the next 10 years with a 1080p native P2 Varicam shooting AVC-Intra 100 with framerates from 1-75fps in 1080p. Thats all I really need.

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I know that the Fujifilm s5 pro still camera has some form of ccd chip which includes sub pixels in a honeycomb formation to provide extra dynamic range. Although initially, there doesn't seem much of a difference when compared to similar class cameras, highlights have a more graduated fall-off, rather than the sudden cut-off point in traditional chips. Furthermore, this would solve any "rolling shutter" issues (it's CCD) and apparently provides a higher effective resolution than bayer cameras. Although it would be expensive for RED to switch to CCD fabrication, surely this would provide something more "film-like". Feel free to correct me if I'm wrong.

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I know that the Fujifilm s5 pro still camera has some form of ccd chip which includes sub pixels in a honeycomb formation to provide extra dynamic range. Although initially, there doesn't seem much of a difference when compared to similar class cameras, highlights have a more graduated fall-off, rather than the sudden cut-off point in traditional chips. Furthermore, this would solve any "rolling shutter" issues (it's CCD) and apparently provides a higher effective resolution than bayer cameras. Although it would be expensive for RED to switch to CCD fabrication, surely this would provide something more "film-like". Feel free to correct me if I'm wrong.

On that subject...

http://www.dpreview.com/news/0807/08070902Kodaksensor.asp

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Hi

My impression is that a lot of people are asking for more resolution (for 8k, even beyond that); however, the motion sickness caused by the NHK Ultra-HD cameras must suggest that we shouldn't be aiming for such great heights in rez - it would be a sad day when cinematographers will have to take that into account while filming...

Anatole

 

EDIT: we don't have anything that can display that much resolution anyway. Wait for cinemas to catch up to 4k first, perhaps?

Edited by Anatole Sloan
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My impression is that a lot of people are asking for more resolution (for 8k, even beyond that); however, the motion sickness caused by the NHK Ultra-HD cameras must suggest that we shouldn't be aiming for such great heights in rez - it would be a sad day when cinematographers will have to take that into account while filming...

With film, cinematographers already have to deal with the problem of having too much resolution for some purposes. So they use filters. From this, Tiffen makes a living.

 

 

 

 

-- J.S.

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