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I really liked it! Its a clear, correct and concise explanation in a cool short with great images.
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Gabriel Devereux - EngineerSee Looking at Lighting – Blade Runner 2049 – Sappers Farm.
From memory it was the equivalent of a light frost on the window. I’ve substituted in any slightly frosted plastic, you don’t want it to be too dense or it will absorb too much of the ingress light.
Then a white (or slightly off-white grey) backing, light this seperately and control any spill onto it. This will be your ‘back-drop’ but it can easily be a frame of any white/gray reflector.
Then above the axys of the AOV out of the window, place your room lighting. This can be a reflector above the outside of the window and above the AOV of the camera, for ease of rigging you can place lights on the ground pointing up into it (remember an ACUTE angle will always be inherently more efficient due to lamberts cosine law).
Note this isn’t supposed to be an exact recipe rather than a general guide for something I’ve tried a couple of times in the past. Diffuse the windows slightly, light your back-drop (can be white and hold it at a certain value) then light the room, a soft even source will light the diffuser on the window more evenly and produce a more even fall-off.
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Gabriel Devereux - EngineerNot Roger. Colour correction is ultimately just digital signal processing, which eventually is just a ton of discrete arithmetic transforms on your image (pixel values).
Both operate with 32-bit floating point precision, so the decider is likely the preferred user interface and the post workflow.
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Gabriel Devereux - EngineerHello!
I believe your question is rather open-ended and would be better answered by browsing the forums, maybe reading cinematography theory and practice, reading the looking at lighting page, and then practising!
In terms of your BMD micro-studio, the early BMD cameras had quite a strong noise pattern at any significant digital gain, so I would recommend rating low!
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Gabriel Devereux - EngineerMaths!
If you have 100% of your energy, you shine it at something, and only 18% is reflected; that’s an 18% grey card! Why do we use it? As a point of reference.
One could use a 50% grey card, but we chose 18% grey. Why? Well, it’s simple! Your eyes see like a camera’s logarithmic container. Our eyes perceive light logarithmically because our photoreceptors adjust their sensitivity based on the intensity of the light. This means that each doubling or halving of light intensity (a stop) is perceived as a consistent change in brightness, even though the actual amount of energy is significantly different.
So, one could use a 50% reflectance card; however, because the step between 100% and 50% is the same as 50% and 25% and 25% and 12%, 50% reflectance is actually not as big a step as one might perceive it to be.
That is why a camera log image looks ‘incorrect’ to us; there’s nothing wrong with it! It’s encoded light similiarly to your photopic vision. One needs to retransform it to a more linear-type signal for our photopic vision to re-encode it logarithmically.
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Gabriel Devereux - EngineerReplying, editing, posting too quickly, all of these issues cause errors.
I tried editing a post and it failed, I tried another reply and it failed.
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Gabriel Devereux - EngineerAs far as I’m aware, this is about how many stops of latitude are above 18% grey at a given EI.
It’s relatively simple to derive this. Have you noted that each time you double your EI (800 to 1600), an additional stop of light is distributed above your 18% grey point?
This is because doubling your signal is essentially increasing intensity by another stop.
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Gabriel Devereux - EngineerConfirming for clarity –
By spherical aberrations, you don’t mean spherical optics struggle to converge light to a point evenly across a plane? That’s why you use aspherical optics—ARRI SPs are as described above corrected with this in mind. Every element is aspherical and very costly.
With the term undercorrected bokeh, are you searching for glass with a very soft feathered edge of the bokeh, similar to ARRI SP’s?
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Gabriel Devereux - Engineer12-bit ARRIRAW stores no more dynamic range or latitude than 12-bit ProRes.
Both use logarithmic encoding to maximize dynamic range.
However, ARRIRAW’s primary advantage lies in its flexibility in post-processing, thanks to its retention of more of the sensor’s original data and metadata.
This has zero impact on rating at a higher ISO and retaining more highlight information due to the above-explained process.
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Gabriel Devereux - EngineerNo, that’s incorrect.
Your codec and your codec’s bit depth do not dictate the amount of latitude it can handle. Extreme compression (outside of the world of ProRes, XAVC-I, etc.) has an impact, but again, it’s spatial compression. It doesn’t compress luminance values more than a bit-depth limiter.
The camera’s logarithmic container almost entirely does that process, which is why we shoot in log.
The goal of a logarithmic container is to encode linear values with an equal amount of logarithmic values past a linear threshold.
The 16-bit unsigned integer photo site value (a linear representation of the energy the photosite receives) is encoded to a 12-bit integer value in its Log-C space.
This compression allows us to record high-dynamic-range imagery visually losslessly in a codec with a bit depth less than our linear value.
A logarithmic container typically exceeds the camera’s requirement. Being able to store more logarithmic values than the camera can produce linearly.
All the previous explanation stands with this reasoning.
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Gabriel Devereux - EngineerSorry*
I made a mistake. If you rate *UP*
That was the only term that was incorrect. As far as I’m aware.
I hope this gives clarity.Infinityvision.tv
Gabriel Devereux - EngineerWhen using a compressed codec, if you rate down you’re still under-exposing the image and retaining more apparent highlight information.
The difference between recording to a compressed codec and recording a raw file is that in a RAW file, each pixel is stored as a single Y value.
This is because sensor RAW information is a single Y (luminance) value per pixel, and we assume values from surrounding pixels to make up the final RGB triplet.
You can still have spatial compression – block type or discrete cosine transform to this 2D plane of RAW Y values.
When changing ISO, you multiply this single Y value per pixel. When a pixel is demosaiced, it undergoes so many functions, such as OETF, WB, etc., that the original ISO function is no longer applicable to the RGB triplet.
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Gabriel Devereux - EngineerI’m sorry, Stip, but you’re incorrect. Spatial compression does not influence the distribution of camera latitude.
The ideology behind this is a camera is a radiometrically linear device. You quantize (convert to digital) the signal linearly; once in this digital domain, the change of ISO by half or double is similar to a 2* or 1/2 operation of that linear quantized signal.
(In post, the manufacturer’s SDK typically linearises the logarithmic container in your NLE when dealing with RAW files to adjust ISO.)
Thus, raising your ISO is essentially ‘under-exposing’ the image. If you under-expose an image without this ISO adjustment (staying at native), it will look darker, with retained highlights. When you amplify this signal in the digital domain (over-expose with ISO), the image will look correct, with retained highlights.
It’s important to note that heavy amplification of finite digital values causes aggressive noise patterns. This is due to the finite values; if you have values of 2, 3, 4, and 5 as your linear quantised native signal and amplify them by a factor of 6 (ISO), your discrete steps become 12, 18, 24, and 30. Large value gaps are easily noticeable by our photopic vision because we perceive light logarithmically (each stop of linear light with the same amount of value).
As a final exciting thought, your photopic vision perceives light logarithmically in a linear realm; our brain does a linear to logarithmic transform, and a camera does a linear to logarithmic transform; this is why the logarithmic container looks incorrect to us, as we’re playing a logarithmic distribution of luminance before the linear to logarithmic conversion in our mind!
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Gabriel Devereux - EngineerIn our world, there are too many variables to give this a definitive answer; however, if one were to view it from a mathematical perspective, technically, everything should stay the same.
Why – everything is relative.
E tan i + E tan R = E tan T
Fresnels Laws –
How much light is reflected?
E (r) = ( n1 + n2 / n1 + n2 ) * E (i)
How much light is transmitted?
E (t) = ( 2*n1 / n1 + n2 ) * E (i)
Notice how it’s proportional to the amount of energy as a linear multiple.
Now, it’s important to note that everything is relative; if you have daylight spill coming into the room and doing the same, you will have a contrastier image. But principally, no nothing changes.
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Gabriel Devereux - EngineerI’ve had to do this often, primarily for heist scenes in several TV shows.
Important things to note: consider your laser akin to a CRT TV.
There is one beam, which has to cover x number of points in a second for it to look like one continuous ray of light, according to our photopic vision.
Of course, anything with on/off cycles and scan cycles (covering all the points) abides by the same logic of synchronicity when shooting a CRT wall or LED display.
I’ve had lasers flicker to the point I’ve had to tell creatives to remove ‘points’ as it was overloading the CPU and couldn’t complete its scan in a factor of 48 or 50Hz.
It’s important the scan rate (the amount of time the laser hits all points in a second) aligns with your framerate, otherwise you will see a roll bar.
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Gabriel Devereux - Engineer
