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  1. #1
    nick mulder's Avatar
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    Filming cine film from screens - optimizing DR - hmmm, I guess a little bit 'zoney'

    Hi,

    I want to shoot video footage off an LCD (or an HD CRT monitor if I can get one) with a 16mm camera. I'm trying to learn how to optimize the output so that it would appear as if the footage were shot on film in the first instance so I'm keen to learn how to optimize the DR/gamma/luminance distribution from screen to film.

    (Although the discussion may involve a digital component the end goal or most of the work is done with film itself so I hope I can keep this 'APUG')

    Anyways, imagine I had a video of a contrasty outdoor sunny scene in which its max and min luminance values hit the actual %100 and %0 values of the screen (I'll make them do that) - I also have dialed in an %18 grey and have taken the following quick readings with a spot meter from the screen:

    EV % 0 = 4
    EV %18 = 7
    EV %100 = 10

    So that is a DR of 6 and I have my baseline exposure set with the %18 grey.

    I think I'm going to be needing to push the film to get the required range of exposure values distributed on the film as it would have if I were to shoot the footage in camera in the first place - right ?

    Is it as simple as that ?

    What don't I know about ? Am I about to get the range correct but send all the nice visual data to peak or shadows ? Will I lose the shadows in the push and have to pump them up a little in the file ?

    I do have some old old film here that was used in the 80's to shoot strictly off CRT monitors, I have noted it is very contrasty compared to standard films, perhaps I should start with that stock as a baseline (?)

    It's not lost on me that I have control over both the file going to the screen (I can play with it 'in post'), the screen itself (brightness, contrast settings) aaaand photochemically with the film itself - I'd like to nail this with the end goal being that I can have all my composite effects and CGI footage have a 'shot with cine and developed in a bucket in the backyard' aesthetic (well, there's more to it than that, but I don't want to get off topic)

    Also - as an aside why isn't it %50 grey ??? How did %18 grey become the mid point here ? The readings show it follows er... 'properly' too

    Kind Regards
    Cleared the bowel problem, working on the consonants...

  2. #2
    ic-racer's Avatar
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    Negative or reversal? If you are shooting negative, it will be easier as you can fine tune when you print. Or are you going back to digital/video?

    If doing reversal, I'd just get a ballpark exposure an send off 25 feet for processing and adjust from there with trial and error. Otherwise you will need the sensitometric data from the film you are using to figure it out beforehand. If shooting reversal you would need to know the range of the film and then base the exposure on the high value on the screen, etc.

    Are you doing this single frame at a time?

  3. #3
    nick mulder's Avatar
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    I can home develop in both neg or reversal - not sure which I'll use in the end - I think neg would make more sense but would require more tuning than reversal once you consider reversals lower range might suit the screen more than the neg which will soak up the light with ease...

    Single frame yes so in essence it's a still shoot - no worries re. refresh rates, flicker etc...

    The sensitometric data will be hard to come by - I'm just going with the idea that at least the DR will be more than 6 stops, I mean you might even get 6 stops on the linear part of the curve huh (?)
    Cleared the bowel problem, working on the consonants...

  4. #4
    nick mulder's Avatar
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    I should have mentioned it will be black and white also - likely some flavor of Plus-X or the old CRT stock I have here
    Cleared the bowel problem, working on the consonants...

  5. #5
    Stephen Benskin's Avatar
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    Have you considered the sinc problem? Film is 24 fps and video is 30. When they show video in motion pictures, they have to use a special process in order to eliminate flame lines, otherwise it will look like the screens at NASA during the Apollo missions.

    18% gray is the perceived visual middle. When you take a gray scale, 18% is the approximate value we see as the middle. It is now considered 19 point something. From a photographic standpoint, 12% is considered middle when the highlight is at 100% Reflectance and the average luminance range is 7 1/3 stops and when it is measured at the film plane. When you incorporate average flare, the highlights at 100% Reflectance fall approximately 0.94 log-H units above the exposure value at 12% Reflectance and the shadows fall approximately 0.94 units below, thus making 12% the middle. The middle for the average scene Reflectance outside of the camera is around 8% to 9%.

  6. #6
    nick mulder's Avatar
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    Quote Originally Posted by Stephen Benskin View Post
    Have you considered the sinc problem? Film is 24 fps and video is 30. When they show video in motion pictures, they have to use a special process in order to eliminate flame lines, otherwise it will look like the screens at NASA during the Apollo missions.

    18% gray is the perceived visual middle. When you take a gray scale, 18% is the approximate value we see as the middle. It is now considered 19 point something. From a photographic standpoint, 12% is considered middle when the highlight is at 100% Reflectance and the average luminance range is 7 1/3 stops and when it is measured at the film plane. When you incorporate average flare, the highlights at 100% Reflectance fall approximately 0.94 log-H units above the exposure value at 12% Reflectance and the shadows fall approximately 0.94 units below, thus making 12% the middle. The middle for the average scene Reflectance outside of the camera is around 8% to 9%.
    Film can be shot in TV speeds also, any frame rate really ... video is any frame rate also - 30 fps (29.97fps) is just NTSC, a frame rate popular in a certain area of the world.

    I really don't want to bog down the thread with this stuff though - as I said above "in essence it's a still shoot - no worries re. refresh rates, flicker etc..." - just really interested in nailing the DR/luminance aspect.

    "18% gray is the perceived visual middle"

    Which again, begs the question: why isn't it %50 grey ? Is there a log/lin going on ?

    Anyway ... I'm just keen on the DR/luminance issue so I shouldn't go off topic myself :rolleyes:
    Cleared the bowel problem, working on the consonants...

  7. #7
    tiberiustibz's Avatar
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    Quote Originally Posted by nick mulder View Post
    Film can be shot in TV speeds also, any frame rate really ... video is any frame rate also - 30 fps (29.97fps) is just NTSC, a frame rate popular in a certain area of the world.

    I really don't want to bog down the thread with this stuff though - as I said above "in essence it's a still shoot - no worries re. refresh rates, flicker etc..." - just really interested in nailing the DR/luminance aspect.

    "18% gray is the perceived visual middle"

    Which again, begs the question: why isn't it %50 grey ? Is there a log/lin going on ?

    Anyway ... I'm just keen on the DR/luminance issue so I shouldn't go off topic myself :rolleyes:
    Because if one averages a typical scene, throwing it completely out of focus, on average that will be 18% grey. Therefore, averaging meters are designed to assume that every scene will produce an average of 18% grey.

    You should be able to set the refresh rate to 24 or a multiple thereof.

    This just strikes me as a difficult proposition. To start just shoot it straight and see if it's passable. With B+W you can probably push to your hearts content. Maybe try an N+1 first?
    --Nicholas Andre

  8. #8
    ic-racer's Avatar
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    In terms of the 18% not seeming to be in the middle, remember the HD curve is drawn with log axes. There is a good description of log vs linear representations of light intensity in that Kodak PDF.

    Since you are going to be processing the film yourself, I would tackle this similar to printing a still negative on paper. Adjust exposure and contrast by trial and error.

  9. #9
    nick mulder's Avatar
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    Quote Originally Posted by tiberiustibz View Post
    Because if one averages a typical scene, throwing it completely out of focus, on average that will be 18% grey. Therefore, averaging meters are designed to assume that every scene will produce an average of 18% grey.

    You should be able to set the refresh rate to 24 or a multiple thereof.

    This just strikes me as a difficult proposition. To start just shoot it straight and see if it's passable. With B+W you can probably push to your hearts content. Maybe try an N+1 first?
    "on average that will be %18 grey" - hmmm, so typical scenes are darker on average ?

    I'm just going to shoot it one frame at a time - automated - but there is no distinction between cine and stills using this method... I've done it before, It works no need to discuss it - ugh! (sorry if I sound ungrateful for the advice, but I did suspect we'd end up talking about this issue as for whatever reason it's the first hiccup in the process)

    This really is just a zone system question - cine doesn't need to come into it.

    Hmmm, I just don't think straight will be acceptable - if the footage is of a scene that should have a DR of sunlight to shadow this will be in excess of the 6 stops that the monitor is giving me...

    I will underexpose and push to compensate, which will solve the DR issue but I want to know how to regain my shadow detail - the luminance distribution might be pushed left/right/up/down the curve in an unnatural fashion - so I'm wondering how to fix for that - how to counter the effects of the push, but only the distribution of the information on the curve not the actual shape of it (which is set for the DR expansion)

    make sense ? Likely I'm wrong somewhere ...

    I think I'll just have to test test test - was hoping to get in the ball park from word go however
    Cleared the bowel problem, working on the consonants...

  10. #10
    nick mulder's Avatar
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    Quote Originally Posted by ic-racer View Post
    In terms of the 18% not seeming to be in the middle, remember the HD curve is drawn with log axes. There is a good description of log vs linear representations of light intensity in that Kodak PDF.

    Since you are going to be processing the film yourself, I would tackle this similar to printing a still negative on paper. Adjust exposure and contrast by trial and error.
    Right - as I expected log/lin - ok, solved!

    Hmmm, the film will either be scanned/telecined or simply shot off a wall with a 4K video camera (I know, I know ... hoops to jump through galore and seemingly contradictory processes but there are reasons why I'm doing it this way, I'm purposefully not bringing them up for fear of prompting off topic discussion )

    I'd like to optimize the neg for the scan/telecine as it will be going through a 'one-light' process and would be best to match the rest of the er, real footage which will be shot in camera (16mm)
    Cleared the bowel problem, working on the consonants...

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