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Generally no, I shoot on the Alexa and stick to a ISO 500 to 1000 range, mostly to control depth of field more than anything. Otherwise I’m mostly at ISO 800. I control my highlights or shadows by exposure and lighting. I control contrast through lighting and by adjusting the LUT using ASC-CDL, mainly for dailies (an adjustment might be to match two cameras or lenses for example, or to deal with a hazy set, etc.)
Either way you are designing a shot that requires the creation of a traveling matte — a chroma key / color difference key (using a green or blue screen usually) is the simplest post method compared to rotoscoping. Now if the actor became a near silhouette against the new background, you can sometimes get away with a white screen and pulling a luminance key rather than a chroma key, but even that may take some clean-up work.
Generally it’s better to take the time in shooting to get something that works well for post than to hand footage to post that needs a lot of work, especially if you don’t know how good your vfx people are or what sort of budget/time constraints they will be under.
Or put the actor in front of a big LED screen where the screen image itself rotates from the old to the new and spin the actor on a platform…
As to whether you heavily push the ISO setting or create a stylized LUT (for monitors and dailies) / or stylized post color-correction, that is entirely project dependent. Your reasons may be practical or aesthetic.
But there are some tried-and-true generalizations:
(1) The simplest approach is often the best.
(2) Garbage In / Garbage Out — the shots you create in camera that come closest to the final look will go through the post process the easiest and come out closest to your intent — whereas the shots that are far from the look you wanted and need a lot of post to fix might not end up close to what you wanted, or you may run out of time and budget in post to get what you wanted.
It’s not as binary as “using natural light = not manipulating the scene” vs. “using artificial light = manipulating the scene” — natural light can be altered in ways (flagging, diffusion frames, etc.) and often artificial light is mixed with natural light if on location.
Cinematographers use light — natural, artificial, or a mix — to create mood and to tell a story. If the goal is a completely realistic and “honest” visualization, the truth is that the lighting could still be entirely artificial.
And what defines “artificial”? If you are shooting a scene in a auto repair garage and you ask the art department to hang a fluorescent shop light over the car being repaired, is that a natural or an artificial light? And if the light is above the frame line so instead you hang a LiteMat LED light instead of a fluorescent, if the effect is more or less the same, how artificial is it? And if the location already had fluorescent shop lights but you switched the tubes from Warm White to Cool White or to color-balanced 3200K or 5600K tubes, is that “manipulating” the scene? Maybe the original tubes would have made the scene look less “natural”, creating a more stylized effect?
Roger generally doesn’t use a separate eye light, except in some of his early works — if you watch “1984”, you can see some use of an eye light when the key is a soft top light in that Gordon Willis style, I don’t know if Roger did this because he was using a silver retention process for the prints and wanted to make sure the eye sockets didn’t get too dark, or if was just an earlier technique of his.
If you study Roger’s work, what you see is that his key is often placed to create a good catchlight in the eye at the same time, i.e. the eyeball is reflecting the key.
In the case of when other cinematographers use a separate eye light right next to the lens, how much contrast you plan on using in the final grade or LUT will affect how much that eye light also adds to the fill in the shadows — if the contrast is a bit higher, with deeper blacks, then the shadow detail drops out a bit more… but the reflection of the light in the eyeball can pop a little more.
Also sometimes “power windowing” the eyeball in post color-correcting and adding some sharpening to just the iris area will make the highlights in the eye brighter too. But that can be time-consuming and tedious for a colorist to track if the actor is moving much.
The size of the reflection of the eye light is a factor too and will not only be affected by the size of the light source but the distance to the subject, plus the size of the close-up — if you get extremely tight, you need to start thinking more about the shape of the eye light since it will be more obvious.
As I said, for a given ISO, the noise in the lower tonal values in the frame are the same whether it is a brightly-lit scene or dimly-lit scene, the only difference is that these lower tonal values take up a larger portion of the overall frame in the dim scene, which probably makes the same noise level now more obvious to the eye, and then once you start color-correcting the image, the changes in noise might be more visible just because so much of the frame has lower tonal values.
But in theory, the noise doesn’t get worse just because a scene is darker, anymore than a scene with normal noise level goes noisy the moment the character switches off the lights or the camera does an iris pull to create a fade-out or the camera pans over to a black curtain, etc. (assuming a fixed ISO setting and a recording with minimal compression and a high-enough bit depth.)
A shadow is just another tonal value in the greyscale. If this were a scene shot in bright sunlight and a person was wearing a black coat, let’s say it was Zone I (-4 stops) in the Zone System, would you be worried about noise in the black coat compared to a scene where a dark wall was in Zone I? They are the same tone so the noise would be the same, for whatever ISO value you set and for whatever viewing gamma (LUT) you pick.
So if you tested the camera at 800 ISO and were OK with the noise in the lower tonal values, you can light a scene as dark as you’d like, the noise shouldn’t change just because the scene was very dim or dark or the actor was wearing black or standing against a black curtain. The only problem is when you change your mind in post and try to manipulate the shadows, push the color in the shadows or lift them, then noise might start to appear.
I think mercury vapor lamps vary somewhat in color just as Cool White fluorescents do, some have a lot more green in them. But you have to factor in how film stocks of the past reacted to that narrow wavelength in the cyan range versus how a digital sensor would react today.
It gets to the point where you might as well just pick a degree of cyan you like — at the saturation level you like — when using an RGB LED rather than worry about the accuracy of recreating a lamp of the past (unless you are trying to match the LED to a real mercury vapor lamp in the shot.)
Here’s a shot from a movie I did 15 years ago which had a real mercury vapor lamp on the corner of the trailer, and one on a streetlamp, shot on Fuji 500T pushed one-stop. But the pool of light over the phone booth was a tungsten parcan gelled with cyan:
From the internet: “The F-stop is also known as the f-number or f-ratio. In photography, the f-number of a camera lens is the ratio of the system’s focal length or capacity to bend light to the diameter of the entrance pupil of the lens. It is also known as the focal ratio.”
In other words, the f-stop is not simply the size of the aperture, it’s a ratio between the focal length and the diameter of the entrance pupil (which is not necessarily the aperture.) So as the focal length changes in a zoom, the ratio will vary — it takes some engineering to design a zoom lens to compensate for this to achieve a consistent f-stop throughout a zoom (and some big zooms still get darker at the most telephoto end even if in general they keep the f-stop consistent.). So you pay more for a constant f-stop zoom, and often the zoom lens might be bigger as well.
The ISO chosen (i.e. your exposure) determines the dynamic range captured, not the recording format if it’s LogC versus Arriraw.
You are forgetting that if you select a higher ISO you are underexposing the sensor so there is no loss in highlight information recording ProRes compared to recording raw and underexposing, and then brightening the shot. You bake in noise and color temperature in ProRes Log C but there is no loss in dynamic range.
In theory in a controlled environment with no practical or natural lighting of its own illumination level, then doubling the light level should give you the same contrast, the brighter lamp bounces back brighter off of surfaces, etc.
However, visually when you shoot at wide apertures and the background goes soft, it can feel lower in contrast because the highlights and shadows in the distance blur over each other — you can see that on a waveform monitor just pointed at a 11-step grey card, if you throw the image out of focus, most of the waveform signal piles into the middle grey zone even though the signal edges still hit the far targets. The in-focus subject doesn’t change, contrast-wise, but with the blurry background softening contrast back there, the contrast can feel less harsh overall.
Depends on your day exterior situation — most of the time, the headroom on the Alexa at ISO 800 is fine. But I suppose you may have a scene where everyone is dressed in white on a sunny day or the camera is pointed into the ocean with hot sunlight glaring off of it where you may want a bit more headroom, but keep in mind that higher ISO means more noise.
I took this vertical photo of mine and cropped it to a horizontal aspect ratio, so the widescreen version has the same horizontal space as the vertical photo. So in this case you can’t say that the widescreen frame has more space in it:
I don’t think any aspect ratio “reduces screen space” overall, you just trade vertical space over horizontal space depending on the aspect ratio. If you see “Oppenheimer” in IMAX film, I don’t think you’d say that when the image expands vertically to 1.43 : 1 15-perf 70mm IMAX from 2.20 : 1 5-perf 70mm that a loss of screen space had occurred.
