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I've recently been exploring the idea of analyzing still frames from films to determine the contrast ratios cinematographers use to achieve a specific look and feeling. This is something I've seen discussed quite often online. However, if I understand the technical aspects correctly, it doesn’t seem possible to do this in a truly reliable and accurate way because: The LUT and post-production workflow can alter the contrast ratios. For example, even if a shot appears to have a 2:1 key-to-fill ratio in the final film, the cinematographer might have originally lit it at 1.5:1 on set, with the LUT increasing the contrast. It's impossible to determine the exact stops used, as you can't extract light levels in stops based solely on an image. While you can see where something falls in terms of IRE, IRE values are linear, not logarithmic, meaning there’s no straightforward way to convert them into stops. Is my understanding correct, or am I missing something? I’d be curious to hear about your approaches to determining the lighting ratios on set —especially in relation to a show LUT.

In both, I'm referring to filming with a Panasonic GH5 on V-Log L 1. Why do we need correct exposure for a particular log? Do colors shift when using wrong IRE? Or is it more for retaining details, not colors? 2. I've seen someone on Youtube (can't remember exactly who) saying that to get proper exposure on V-logL, your subject should be at 42 IRE. Using an 18% gray card, he adjusted the exposure until it's roughly 42 IRE. So i thought to myself that I can adjust exposure even when the subject/actor hasn't arrived on the set yet. I'll hold an 18% gray card on where his face would be and put it at 42 IRE on my waveform (or false color monitor). However, I've read somewhere that IRE is different for different skin tones, like 55 for caucasians. So, should I just expose my grey card to 42 IRE of just wait for the actor to arrive and expose for his skin tone? Which one is correct? Thanks advance! God bless.

There has to be a correlation right? Lets say I shoot a 18% gray card and it is sitting at 50 IRE on a waveform monitor. What would an increase of 1 stop read? A decrease of 1 stop? I'm trying to create some customized false color LUTs just for my own purposes to analyze images in resolve. But I'd like to be able to say ok, gray = middle gray, one stop over that should be yellow, two stops over that should be orange, three stops over that should be red, etc. but I'm struggling with knowing how to measure the exposure gains. Thanks!

Hi everyone. I'm very interested in being able to breakdown lighting ratios from inspiration using the same set of standards that I use when shooting (mapped IRE false color values on a production monitor). However, I'm having a bit of trouble grasping the best way to accomplish this. It's clear to me that images read best on camera between 2 stops over/under key. I'm shooting in slog3 on FS7, but monitoring in rec709 LUT on my monitor. I've brought up a chart from the app "LutCalc" that displays relative IRE/stop values for a certain monitor LUT- in this case going from slog3->rec709(800%). (Attached) So from what I understand here are the following values for +- 3 stops from key. -3 = 14% -2 = 20% -1 = 30% 0 = 44% +1 = 63% +2 = 84% +3 = 97% Does this mean that if I assign each relative stop to the corresponding IRE value in False Color using the same monitor I shoot with that I will be able to accurately breakdown lighting ratios and seamlessly recreate said ratios on set by matching colors?