1. Deconstructing F-Log2: The Science

Fujifilm's introduction of the F-Log2 profile on its X-Processor 5-equipped cameras represents a significant advancement for filmmakers seeking the highest level of image quality and post-production flexibility. More than a simple iterative update, F-Log2 is a fundamental re-engineering of the company's approach to logarithmic video capture, rooted in the principles of traditional cinema film.

1.1 The Logarithmic Premise: Capturing Light, Not Looks

Standard video formats, like Rec.709, are "what you see is what you get," with color and contrast baked in. This limits creative freedom. Logarithmic recording is different. It uses a log function to compress a vast range of light values into the video file. The footage looks flat and desaturated initially, but it's packed with tonal and color information, giving you immense control in post-production. It's crucial to distinguish this from RAW video; a Log file is a standard video file where ISO and white balance are baked in, whereas RAW is unprocessed sensor data.

1.2 F-Log2 vs. F-Log: An Evolutionary Leap

F-Log2 is a major upgrade over the original F-Log. Independent tests show F-Log2 offers around 1.3 stops more usable dynamic range than its predecessor. This extra latitude is mostly in the highlights, preventing blown-out skies and bright lights. The color is also more robust, with a greater "density" that holds up better to aggressive grading. High-end bodies also get F-Log2 C, a variant with an even wider color gamut for superior accuracy.

1.3 The Technical Blueprint and Camera Support

F-Log2 is exclusive to the new generation of X-Processor 5 cameras. Its technical design maps 18% middle gray to ~38 IRE and lifts the black point to preserve shadow detail, emulating cinema film. This synergy between sensor and processor is why F-Log2 cannot be back-ported to older cameras.

2. The Decision Matrix: When to Use F-Log2

Choosing F-Log2 means committing to post-production. It's not always the best choice. Here's how to decide.

2.1 The High-Contrast Imperative

F-Log2 shines in high-contrast scenes: bright sunny days, backlit subjects, or interiors with bright windows. In uncontrolled environments like documentaries, using F-Log2 is like technical insurance, capturing maximum data in case lighting changes unexpectedly and preventing irretrievably lost highlights.

2.2 The Workflow Trade-Off: F-Log2 vs. Eterna

For fast turnarounds or if you're new to color grading, Fujifilm's Eterna profile is a fantastic alternative. It delivers a cinematic, low-contrast look straight out of the camera, requiring minimal tweaking.

2.3 The Low-Light Consideration: A Calculated Risk

F-Log2's high base ISO can be a challenge in low light. The problem isn't F-Log2 itself, but *underexposing* it, which amplifies the noise floor. In a dark, low-contrast scene, the original F-Log is often a cleaner choice. However, if a low-light scene also has bright elements (e.g., concert lights, street lamps), F-Log2 might be the only way to avoid clipping those highlights, making it a necessary compromise between highlight retention and shadow noise.

3. Mastering Exposure: The F-Log2 Index Test

Properly exposing F-Log2 requires a deliberate, tool-based approach. Forget auto-metering; it's time to take control.

3.1 Managing the High Base ISO

The base ISO (1000 or 1250) is where the sensor delivers its optimal dynamic range. In daylight, this high sensitivity means you can't shoot with a wide aperture without overexposing. Therefore, a high-quality Variable Neutral Density (VND) filter is essential, not optional. It allows you to control light and maintain creative control over depth of field. Avoid stacking cheap filters, which can cause color shifts and "X-pattern" artifacts.

3.2 Reading the Tools: The 85 IRE Ceiling

A unique quirk of F-Log2 is that it appears to "clip" on a waveform monitor at around 85 IRE, not 100 IRE. This is intentional. It's a gentle highlight roll-off, like a film stock's "shoulder," preventing harsh digital clipping. Even when the waveform shows a flat line at 85 IRE, there is still usable detail in the recording. For exposure, treat 85 IRE as your new clipping point.

3.3 The Second Gain Circuit: A Low-Light Strategy

While not an official "Dual Native ISO," Fujifilm cameras exhibit a similar behavior. At a certain point (e.g., ISO 4000 on the X-H2S or ~ISO 2000 on the X-T5), the camera switches to a second, cleaner analog gain circuit. This means footage at ISO 4000 can look less noisy than at ISO 2500. If you must push your ISO in low light, it's often better to jump directly to this second gain point instead of using intermediate values.

4. The Digital Darkroom: Post-Production & LUTs

Well-exposed F-Log2 footage is just the start. The magic happens in post, where you transform the flat image into a polished final product.

4.1 The Foundational Grade: Conversion LUTs

The simplest starting point is a conversion LUT, which translates your F-Log2 footage into a standard Rec.709 viewing format. Fujifilm provides official LUTs for free. Crucially, apply all your primary corrections (exposure, white balance) before the LUT in your editing software's signal chain. Applying corrections after the LUT is a destructive process that works on already-compressed data.

4.2 The Professional Workflow: Color Space Transform (CST)

For the best quality, use the Color Space Transform (CST) tool in DaVinci Resolve instead of a LUT. A CST is a precise mathematical conversion that retains more color information and avoids artifacts. This is the standard for professional, non-destructive, scene-referred color grading.

4.3 The Creative Touch: Stylistic LUTs

After your footage is corrected, you can apply a creative LUT for a specific look. High-quality options from developers like Phantom LUTs or Buttery LUTs are designed for F-Log2. For deep film emulation, plugins like Dehancer offer comprehensive tools. Always apply them on a separate node and adjust the intensity to taste to avoid an overly "baked-on" look.

5. Advanced Techniques & Best Practices

Beyond the basics, a few key practices can elevate your F-Log2 footage from good to great.

5.1 Perfecting In-Camera Setup

Your final image quality starts in-camera. Before you press record, dial in these settings for the cleanest possible source file:

• Noise Reduction: Set to the lowest value, typically -4. In-camera NR is destructive and can't be undone. It's better to apply more sophisticated NR in post if needed.
• Sharpening: Set to -4. Like NR, in-camera sharpening can create unwanted artifacts. Apply sharpening as a final step in your grade.
• Codec: Always choose the highest quality codec available. Apple ProRes or All-Intra H.265 will hold up far better in grading than more compressed Long-GOP options.
• White Balance: Set a custom white balance in-camera using a gray card. Unlike RAW, white balance is baked into Log footage and is much harder to correct perfectly in post.

5.2 Monitoring with Preview LUTs

Staring at a flat, gray F-Log2 image on your camera's LCD can make it difficult to judge focus and composition. Use the camera's built-in F-Log2 View Assist feature. This applies a non-destructive Rec.709 preview LUT to the monitor and EVF, showing you a normalized image while the camera continues to record the flat F-Log2 file. This gives you the best of both worlds: an easy-to-view image for monitoring and a flexible log file for post-production.

6. Conclusion: Key Takeaways

F-Log2 is a powerful tool for Fujifilm filmmakers, offering cinematic dynamic range and color. Mastering it requires a shift in thinking away from "what you see is what you get" and towards a deliberate, data-driven approach. By understanding its strengths and limitations, you can unlock the full potential of your X-Processor 5 camera.