silvan schnelli

@Steven West Thank you for the reply. Ya I suppose it really does depend on the scene and the information I want retain. I guess it is quite straightforward in away and that I probably just need more experience with filming silhouettes to figure our what exposure, and how many stops over or under works best for what types of scenarios and desired atmospheres.

@David Mullen ASC Thank you a lot for the thorough responses. It seems that both you and your wife are amazing cinematographers.

@David Mullen ASCFirst and foremost thank you for the replies. So in general how many stops under do you tend to aim for the silhouettes to be, do you ever try to keep them at a certain scene to preserve some detail or to perhaps have a better SNR, so the quality of the silhouettes aren't as noisy, or do you just naturally let them fall into a certain exposure level. You also mention that you would meter for the shaft of light and then set it one stop over, is that just intuitive that you can see that that shade is roughly one stop over middle grey. I also in general I had a question, l if we take the Alexa mini with its 7.8 overexposure latitude and 6.7 underexposure latitude to film a contrasty scene such as in "Vertigo" where you would want detail in the bright neon sign and also detail in the shadows, where do you find that your shadows and highlights fall into (or such as in your example from "Big Sur"). I remember seeing an answer from you on another forum topic where you mentioned that people used to light scenes within 11 stops but now its different. Do you find yourself often having elements in a scene which are found at the lower and upper bound of the dynamic range and does it even make sense to light this way, to try to reach the limits of the dynamic range? Another example perhaps, a very contrasty scene where the whole set is practically in darkness and you would still want details in the shadows, but at the same time there is a bright practical in the scene. Thank you

Ups I meant to say "hence a high EI", not Low EI for more highlight detail and then "however this would lead to a worse SNR", not better SNR. Apologies

How would you go about metering and exposing for a scene with a silhouette, such as in this cropped frame from Alfred Hitchcock's Vertigo? I often find that exposing for the background to be middle gray does the trick, but I'd much rather be certain on how to do it. What would I choose to expose to be middle grey, should I try to correctly expose it and try find a source that most resembles it? Also how would you go about choosing the distribution of the highlight and shadow latitude, I understand that this obviously depends on how I want the scene to look and the scene in itself, but do most people aim for? Do you tend to try and keep details in the shadows of the silhouetted figure? In this scene for example, at least to me, there seems to be high distribution in both the highlight and shadow latitude, so perhaps a balanced EI would be a better choice. However, I suppose since the figure is meant to be silhouetted anyways, so perhaps we do not want shadow details and rather have more highlight information for the neon sign, hence a low EI would be better? I guess this would also improve the SNR. I aware these are a lot of questions, so thank you for taking your time and reading this.

@David Mullen ASC Ah I see very interesting. Thank you a lot for the reply. I also went back to reread the Wikipedia on photographic processing and Kodaks essential reference guide for filmmakers and the whole process and way film stock is structured is much clearer now.

@Robert HoullahanInteresting information. I’ll have to check it out. thank you

@Karim D. Ghantous Thank you for the response and the diagram. It’s interesting to see the differences in their over- and under- exposure latitudes, between film and digital sensors.

@David Mullen ASCThank you a lot for your response. However, if we ignore for a second that it would be mostly be disadvantageous to underexpose film, is it reasonable to say that film works in many ways similar to digital then? You underexpose for more highlight latitude and overexpose for more shadow latitude. I feel like a changing a digital sensors EI and then exposing accordingly shares many parallels to rating a film stock at a different EI and then printing up or down. It seems to me that the EI on a camera basically encompasses that mechanism, as to my knowledge EI for digital sensors is similar to an “exposure LUT”. I was wondering what your thoughts were on this. I also am confused about the tighter grain patterns by overexposing, doesn’t that lead to more grain, because we expose more silver halide crystals or is it cause we print it down? Or does overexposing lead to less shot noise like with digital sensors? And lastly I thought that digital cameras responded similar to film as the log curves are based on the original Cineon scans of negative color film. Although it confuses me why, for example LogC4 didn’t roll off at the top.

From most of the sources I have read, it was always written than overexposing film (thicker negative) would lead to increased latitude in the highlights and underexposing film (thinner negative) would lead to increased latitude in the shadows (the opposite is true for digital which makes sense). However, I am currently reading Glen Kennels excellent book on "color and mastering for digital cinema" and am now a bit confused if what I have read regarding overexposing = more highlight detail and vice versa is true. Perhaps I must be misunderstanding something. 1) Now in this book he mentions that to obtain more details in the shadows, you would want to overexpose to obtain a heavy negative and then print down to extend the range into the shadows. This would lead to deeper blacks as he shows in a diagram, but as he also mentions, is that can uncover "details that might otherwise have been lost". As well as to underexpose the negative to assure that all the highlight information is obtained in the negative. Perhaps I am confusing underexposing to ensure that all the highlight details are captured and overexposing to obtain a larger range of details in the highlights as the same thing, when in reality they are different. However, it seems like it would make much more sense to underexpose and then print up to obtain more details in the highlights. Furthermore, I don't understand how underexposing would lead to more details in the shadows compared to as is mentioned in the book, overexposing and then printing down. I hope someone could maybe help me clear up some of my confusions regarding this. 2) Another point I would like to mention is that overexposing the negative is said to lead to more contrast; however, when I'm looking at the curve of the color print film, the gamma of the curve seems to be the same, which is theoretically the definition of contrast in projected print. Although I thought that perhaps the reasoning is that we now have a larger difference between the minimum and maximum amount of density on the color film print. Is this correct?

I have been reading the ASC article on exposing for film (https://theasc.com/blog/shot-craft/shot-craft-the-art-of-exposing-film) and am very interested in the steps involved in the color timing and printing process of film, as well how they may vary when using the Hazeltine and doing it through a DI. However, I can not seem to find any extensive sources that go really in depth on these topics. My best bet right now has been Wikipedia. I sadly have not had the chance yet to film anything on photographic film and experience the process after acquisition, so I would like to read about it. I would also really appreciate it, if perhaps some of you could share your knowledge on how correcting for an overexposed scene acquired on photographic film differs when corrected with the Hazeltine and the DI. In addition to that, I would also be curious to how it differs from correcting an overexposed scene acquired from a digital sensor.

@Robin Phillips Interesting, I'll definitely have to deeper dive into this subject. Thank you for the extensive reply.

@Robin PhillipsAh okay yeah I see that makes sense to me. However, that arises a lot of question from me in regards to Tyler Purcells first point. (Not saying he is wrong just that I am confused) “1) Bandwidth (bit rate) is king. A 1080p (2K) distribution, will have WAY less bandwidth than a UHD (4K) distribution. You always want to distribute in 4k because the more bandwidth the better it will look. The difference between 4:2:0 (standard home streaming) 4:2:2 and 4:4:4 on someone's home TV is unnoticeable in 4k, but in 1080p, eh you can see if it you have some hard color lines between the red and blue channel. ” Since you need higher bandwidth for 4K and innately less for HD, as you mention, why don’t we just user a higher bandwidth for HD, wouldn’t that improve the quality then. I am just confused cause the argument is to shoot 4k for more bandwidth but it also requires more bandwidth and at constant bandwidth a 1080 would look better than 4k. I’m sure I’m misunderstanding something here, or do we just use the minimum amount of bandwidth required for streaming at each resolutions, well in that case shouldn’t it just all be the same cause 4k needs more cause it’s bigger so it would playback at the same quality as 1080 which needs less cause it’s smaller? And yeah I think I’ll definitely have to run some of my own tests to see what the noise and quality difference will be like in regards to my original question of downsampling. thank you for your time and replies.

I have read ARRI's whitepaper on dynamic range and how the EI is used to assign which signal value we want to choose as middle grey, which ultimately allows us to control the exposure latitude around middle grey. I've also read that the way ARRI does this is by only allowing us to shoot at its native ISO 800 (or maybe as some say its 400) and that changing the EI is like adding an exposure LUT on our image. This would make sense to me, because it would explain how the dynamic range (SNR=1 to full well capacity) is able to stay constant at different EI, because it doesn't operate by increasing the gain of the signal. (It would also explain why its they use the nomenclature EI) Nevertheless, I would like to know how they do this and if what I have read is correct?

@Robin Phillips Ah I see very interesting. I am not to familiar yet with bit rates and especially how they are tied to resolution. Intuitively I assumed that higher resolution footage required higher bitrate and lower resolution footage required a lower bitrate, but that due to this they would ultimately playback at the same quality. However what I seem to be getting from your answers is that this isn't the case. I suppose I still don't understand the bitrate is king statement, are there any links I can refer to, to learn more about this. Now regarding the scenario that prompted the question, well there are two reasons. One is that we have a film exercise where the professors want us to have the final output in 2k and wanted to know if it makes sense to film 4k and then down-sample to improve SNR (besides the obvious benefit of being able to crop at 4k). So it would be important for me to know how much down-sampling from lets say ProRes 422 at 4k to 2k differs, to filming ProRes 444 at 2k on a 4k sensor (with respect to all the things I mentioned in my original post). I am also planning to shoot many tests in which I'd like to explore and discuss all the different methods in which the SNR can be improved when filming and down-sampling would be one I'd like to tackle in this experiment.

@Tyler PurcellThank you for the very informative answer on perhaps the most important question, addressing in which resolution I should film in. I will definitely have to do more research into bandwidth and how that ties into resolution. I am surprised to hear that 2k is a dead format, as i thought that many movies were still mastered in 2k, or do you really just mean 2k acquisition? Nevertheless, I would also still like to know the answer to some of my other questions, regarding the effectiveness of Downsampling.

I've read that down-sampling an image from 4k to 2k can yield benefits in the sense of: A 4:2:2 4k image down-sampled to 2k, would result in a theoretical 4:4:4 2k image, leading to a chroma resolution similar to the luma resolution. By binning the pixels, you average random variations (reducing noise) and boost non-random variations (signal), leading to an increase in the SNR It also increases sharpness, although I am not sure how. Now these points all make relatively sense to me and I'm sure that it also depends on the algorithms used for the down-sampling. However, my question is how does this down-sampled 4:2:2 4k image compare to a 4:4:4 2k image, will it have better chroma resolution at lower storage, will it have less noise, will it be sharper, or is the down-sampled 4k image just better than a 4:2:2 2k image but the same as a 4:4:4 2k image. How much does the algorithm play a role? And ultimately, if I were to film something would I be better off down-sampling 4k to 2k, or should I just film 2k. I guess this leads me to another question, when I film 2k on a native 4k sensor and use the whole sensor, does it theoretically bin the pixels automatically, so doing filming 4k and then down-sampling in post would be redundant?