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Hi Roger and community,
I am currently doing a research paper for my school, and I am tasked with answering the question: “Reading the film stock curve and selecting a stock based on their color & contrast representation.”
I’ve done some preliminary research into the subject, reading Kodak’s Sensitometry Workbook along with a handful of film manuals at the library, and have interpreted the essay prompt as “How can the characteristic curve and spectral-sensitivity chart inform a decision on how a film stock will perform?”
I decently understand the concepts of contrast/gamma, how to feel out latitude of a stock from a quick glance at its D logE cuve, and the differences in sensitometry between reversal and negative stocks.
However, I wanted to reach out to the community and ask any cinematographer who has worked a lot with film – or is currently working with film on a show – how reading the spec sheet has informed your decision on a film stock. What did you do with the information? How has it led to your testing phase? Is it even important in the end versus real life testing?
In addition, I had one technical question that deals with the RGB curves in the D logE chart when it comes to normal process vs push/pull process.
As an example, let’s take a look at Kodak 200T listed at this pdf link below:
In the contrast curve (named “sensitometric curve”), it appears that Blue and Green curves are slightly steeper when compared to the Red curve. I want to confirm that this means the gamma of the individual channels for blue and green are higher, meaning there is “higher contrast in those colors.” Practically, this means that I can expect more Blues and Greens as exposure go up into the highlights, versus the shadows?
Furthermore, say I push this stock by 1-stop. If I charted the resulting sensitometric curve of the developed negative, the toe would remain the same… but the shoulder would be lifted by that 1-stop compensation. Does this 1-stop push get evenly spread across the RGB channels? If so, does that means the steeper gammas of Blue/Green compared with the Red channel becomes even more exaggerated? In theory, I would expect some more blue/green in the highlights?
Please let me know if I have this concept wrong. Also, would love to hear any of your personal experiences or thoughts on this topic as a whole.
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