OPTICLOG
IMAGE ANALYSIS
Why this tool?
As a DP and a Colorist, I’ve always believed that a great grade starts with a perfectly exposed frame. I created OpticLog to empower fellow creators with a professional-grade monitoring suite accessible from any browser.
Beyond standard analysis, this tool integrates a sophisticated 15-stop exposure mapping system. By translating raw luminance into logarithmic stops, it allows DPs and Colorists to precisely calculate contrast ratios directly from a still—effectively acting as a digital light meter. Combined with a custom-built Vectorscope and RGB Parade designed to mimic high-end grading monitors, OpticLog ensures your creative vision is always backed by scientific accuracy.
Waveform
Vectorscope
Histogram
RGB Parade
The Math Behind the Mood: Building a Pro-Grade Image Analysis
In cinematography, "eyeballing" your exposure is a luxury we can rarely afford. Whether you’re on a high-end commercial set or grading a music video, precision is the difference between a clean image and a noisy disaster.
To bridge the gap between production and post-production, I’ve developed OpticLog - a web-based analysis tool designed for DPs and Colorists. But this isn't just a color filter; it’s a math engine. Here’s a look at the logic under the hood.
1. Beyond RGB: The Luminance Logic
Computers see images as a grid of RED, GREEN, and BLUE pixels. However, the human eye doesn't perceive these colors with equal brightness. To build a tool that truly reflects exposure, we first have to calculate Luminance (Y).
Using the Rec.709 standard, the tool applies a weighted mathematical formula to every single pixel:
This ensures that the "brightness" we analyze matches exactly how our eyes and our monitors see the world.
"Generic" Standard False Color based on IRE signal.
Movie: Sicario (2015)
Director: Denis Villeneuve
Cinematographer: Roger Deakins
The Problem with "Generic" False Color
One of the biggest frustrations on set is the lack of a universal standard for False Color. Most third-party monitors implement a generic, linear IRE-based scale that varies wildly from brand to brand. In these systems, colors are often arbitrarily assigned to brightness percentages, making it nearly impossible to maintain exposure consistency when switching between different monitor hardware.
The fundamental flaw of generic False Color is that it treats light linearly, whereas cinematography is a world of Stops. This is why professional standards like ARRI’s False Color or Ed Lachman’s EL Zone System are so revered—they are sensor-based and logarithmic.
OpticLog was built to eliminate this guesswork. Instead of relying on inconsistent IRE values, it uses manufacturer-specific mathematical transforms to 'de-log' the data. By mapping exposure to a 15-stop scale relative to 18% Middle Gray, OpticLog provides a constant, scientific reference that remains accurate regardless of the display hardware. It brings the high-end precision of an ARRI or a specialized EL Zone monitor to your browser, ensuring that your 'Green' is always Middle Gray and your 'Yellow' is always exactly one stop over, every single time."
EL Zone with Rec.709 image
Movie: Sicario (2015)
Director: Denis Villeneuve
Cinematographer: Roger Deakins
2. The Magic of Logarithms (EL Zone System)
The crown jewel of this tool is the EL Zone System, inspired by the legendary Ed Lachman, ASC. Unlike traditional IRE scales that are linear, EL Zone is Logarithmic.
Why does this matter? Because light works in "Stops." Every time you increase your exposure by 1 stop, you are doubling the amount of light. To map this, the tool uses a Base-2 Logarithm:
L pixel = Linear Luminance
L 18% Grey = Linear Luminance of 18% Middle Grey
By calculating the distance from Middle Gray (0 stop), the tool maps 15 distinct zones. When you see Yellow, the math tells you you’re exactly +1 stop above gray. When you see Blue, you’re -3 stops below. It turns your image into a literal light meter map.
EL Zone with Slog3 image
Director: Ho Hai An Khuong
DOP: Duong Truong
3. Reverse Engineering the Sensor (Multi-Gamma Support)
The most challenging part of building this was handling Log Profiles (S-Log3, LogC3/C4, REDLog3G10). A raw Log image looks flat and gray because the camera "squeezes" the data to save dynamic range.
To show the real exposure, the tool performs an Inverse Gamma Transform. It uses manufacturer-specific math to "de-log" the pixels back into a Linear state before calculating the stops. This means if you upload an S-Log3 file, the tool "undoes" the Sony curve to tell you the truth about what the sensor actually saw on set.
AWG4/LogC4 Reference Image
4. Vector Math & The Skin Tone Line
On the Vectorscope, we aren't looking at brightness; we’re looking at Chroma (Color).
The tool converts RGB data into U and V coordinates. One critical feature I’ve included is the Skin Tone Line. Mathematically, regardless of ethnicity, human skin color falls on a very specific phase in the color spectrum appx ~103 degree on the vector map.
By drawing this line through the data, the tool allows you to see instantly if your subject's skin is leaning too green or too magenta, ensuring perfect skin reproduction every time.
Scopes in Davinci Resolve
