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    #31
    Senior Member lpcvideo1's Avatar
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    Good question. I assumed it was cropping the image.


     

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    #32
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    I was under the assumption that the extra ".4K" was overscan to see what is just outside frame.
    "I've heard that this project is impossible... hehe" ~ Jim Jannard
    The Pursuit of Happyness


     

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    #33
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    The full pixel array is listed as 4900 X 2580. The active pixel array is 4520 X 2540.

    http://red.com/techspecs.htm

    2540p (RED-speak) converted to 4K is still a downrez by my math.


     

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    #34
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    at 2540p you can on crop, not downrezzing about it!


     

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    #35
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    Quote Originally Posted by david farland
    at 2540p you can on crop, not downrezzing about it!
    Hmmm... Don't know. I had assumed that 2540p (full active sensor array) to 4K was a downrez and not a crop. Much like 4K to 2K scaled is a downrez. The literature speaks of shooting full S35mm @ 4K. If a crop as you suggest, then at 2540p would you not be shooting off the lens, so to speak?

    Can anyone confirm? 2540p to 4K - a downrez or a crop????


     

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    #36
    Red Team Rob Lohman's Avatar
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    4.9K --crop--> 4.5K (look around in viewfinder) --crop--> 4K

    As correctly indicated by others no resampling / resizing in RAW recording mode (only cropping). RGB recording modes have some resizing options (2K, 1080p, 720p)

    2K in RAW would be cropping (or windowing the sensor is what basically happens).


     

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    #37
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    Quote Originally Posted by Muttondraw
    I know the sensor size is over 4k but as you are using a Bayer arangement to sense colour won't actual imaging resolution be slightly lower than that. Probably making it pretty much equivalent to 35mm film res. I am not trying to knock the resolution, I am very happy with 35mm res, I just though it was worth establishing the difference between number of pixels and actual resolution imageable.

    Of course if I have got the wrong end of the stick please put me straight.
    Martin
    In a Bayer patterned sensor, each pixels is biassed to either Red, Green or Blue. Just because the pixels are biassed to one color or another, does not mean that pixel doesn't know the wavelength of light (color) that's striking the photon receptors.

    Most people I've found that complain about Bayer patterned sensors "not being full resolution" don't understand that just because a pixel has a bias, it doesn't mean the pixel stops doing it's job.

    We use very sophisticated algorithms to maintain maximum resolution and sensitivity. It wouldn't surprise me if the folks at Red do something similar.

    I.
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    Illya Friedman
    Hot Rod Cameras

    My hilarious twitter twocks @hotrodcameras


     

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    #38
    Senior Member Muttondraw's Avatar
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    Quote Originally Posted by Illya Friedman
    In a Bayer patterned sensor, each pixels is biassed to either Red, Green or Blue. Just because the pixels are biassed to one color or another, does not mean that pixel doesn't know the wavelength of light (color) that's striking the photon receptors.

    Most people I've found that complain about Bayer patterned sensors "not being full resolution" don't understand that just because a pixel has a bias, it doesn't mean the pixel stops doing it's job.

    We use very sophisticated algorithms to maintain maximum resolution and sensitivity. It wouldn't surprise me if the folks at Red do something similar.
    Interesting, but are you saying you can image at the full sensor pixel resolution without any artifacting relating to the reduced frequency colour sampling, or that you maximise resolution achievable? I would have assumed the latter, that is certainly what happens with still cameras using Bayer pattern sensors.

    I would like to underline the point that I am not complaining about this issue though, I just thought it was worthwhile pointing out that there is a difference between the number of pixel you count on a sensor and the actual resolution you can achieve from that sensor if you are using the Bayer approach, rather than using something like the Foveon sensor. In the particular case of the Red camera with an active pixel area of 4520 x 2540 I would assume they are probably going to achieve 3k to 3.5k resolution. Maybe Graeme would contribute to this thread, I am sure he could put some more accurate figures to this,

    As soon as a comparison is made to imaged resolution then we have to be comparing to the imaging resolution achievable by the sensor.

    Martin


     

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    #39
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    It's pointless to compare bayer to foveon when foveon's have neither the resolution nor the fps needed for a digital cinema camera. And although foveon cameras never seem to come with an OLPF, they certainly do need a hefty dose of anti-alias filtering as you can see from the severe aliassing artifacts in any foveon image. And 3 chip systems don't work with the size of sensor we're using, so they're out of the running too.

    Say you're shooting 4k raw. You're recording 4096x2304 pixels. And that's the resolution of the final RGB image also. What the measured resolution will be is something smaller due to the optical low pass filtering which is necessary to avoid nasty aliassing artifacts occuring. It's that filter that puts an upper limit on the measured resolution, and the bayer demosaicing algorithms can get as close as you want to that, given enough render time :-) Practical algorithms can get very close though.

    I state that the figure is > 70% which I think is accurate enough, because one of the nice things about a good demosaic algorithm is that it doesn't look uprezzed and artifacty the way it would look if you took a 30% smaller image of "full resolution" and blew it up to 100%. A good demosaic can look rather nice and smooth, and film-like in a good way, as the images we showed at IBC demonstrated.

    Graeme
    www.nattress.com - Film Effects and Standards Conversion for FCP
    www.red.com - RED - 4k Digital Cinema Camera


     

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    #40
    Senior Member Muttondraw's Avatar
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    Quote Originally Posted by Graeme_Nattress
    I state that the figure is > 70% which I think is accurate enough, because one of the nice things about a good demosaic algorithm is that it doesn't look uprezzed and artifacty the way it would look if you took a 30% smaller image of "full resolution" and blew it up to 100%. A good demosaic can look rather nice and smooth, and film-like in a good way, as the images we showed at IBC demonstrated.

    Thanks for that Graeme. I saw the footage at IBC and it looked stunning

    So going back to the original point. Assuming the > 70% figure. Would it be fair to say that the maximum resolution you could capture using the 4K on the RED one would probably be about equivalent to the top end of what you could get off a 4K scan of 35mm film in ideal circumstances (assuming Jims figure of 3.2K for 35mm)

    Would there be much of an issue upon the use of a B4 lens for 1080p, assuming the lens is only going to be able to use 1080 x 1920 pixels, or are the effects of the mosaic going to be swamped by the anti alias filter again. Would there be a significant resolution advantage in using S16 lenses at 2K instead and then downrezzing to 1920?

    Martin
    Last edited by Muttondraw; 10-20-2006 at 07:24 AM.


     

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