Short answer
Log footage looks flat because it is not a picture yet. A log curve stores scene brightness so that each stop of exposure takes an equal step of signal, which spreads fourteen or so stops evenly across the file and puts mid-grey near 40 per cent instead of where a display expects it. Shown without the transform that turns scene values into display values, it reads as low in contrast and colour. The flatness is the unspent range, and each camera maker's curve needs its own transform.
A stop is a doubling of light. Stored linearly, the brightest stop a sensor records uses half of all the code values in the file, the next a quarter, and the shadows are left with a handful each. A logarithmic curve reverses that: ARRI describes its Log C as an encoding in which the signal rises by a fixed amount for every stop of exposure. Every stop then gets a similar number of code values, which is what makes a ten-bit recording of a wide-range scene gradeable without the shadows breaking into steps.
Negative film already behaves this way: the density it builds is roughly proportional to the logarithm of exposure over the straight part of its curve. When Kodak brought its Cineon scanning and recording system to market in 1993, scanned negative was stored as numbers that tracked density. ARRI states that the C in Log C stands for Cineon. Sony describes S-Log3 as closer in character to film than its predecessor. Digital cinema cameras adopted a film-scan convention so that the tools and habits of film post-production would carry over.
A monitor assumes the signal it receives is display-referred: finished values, with black near the bottom and white near the top of the range. Log footage puts black well above zero and holds its highlights far below the top to leave room for what is brighter still. Sony's guide gives the number plainly: with S-Log3, an 18 per cent grey card is output at 41 per cent. Displayed as it is, everything sits in the middle. Saturation looks low for the same reason, and because the camera's wide colour space is being shown as if it were the display's narrower one.
There is no single log. ARRI's LogC3 and LogC4, Sony's S-Log3 and RED's Log3G10 are different curves paired with different sets of primaries, and LogC4 is not a revision of LogC3 but a separate space. A transform built for one is wrong for another, sometimes subtly. This is the commonest cause of footage that looks nearly right: skin slightly magenta, highlights that roll off too early. Identifying the encoding and the colour space from the camera's metadata, not by eye, is the first step of any grade.
The recording stays in log; the monitors show it through a transform. On House of the Dragon one show lookup table was used throughout, built to display the picture a stop darker than it was exposed, so that the crew judged a moody image while the recording kept a healthy exposure. Roger Deakins viewed Blade Runner 2049 on set through a table he had used on an earlier film. In both cases the look seen during the shoot was a decision about display, held apart from what was written to the card.
| Encoding | Publisher | Edition | What it is | Limit of this record |
|---|---|---|---|---|
| Cineon | Eastman Kodak | System introduced 1993 | Kodak's digital film system: a scanner, a recorder, workstations and an open file format for scanned negative. Its logarithmic, density-based encoding is the ancestor of camera log curves, and its file format became DPX. | Kodak's handbook dates the system; the encoding's code values come from Kodak documents that were not read, so none are given. |
| DPX (SMPTE ST 268) | SMPTE | 268M-1994; revised 2003; ST 268:2014 | A frame-per-file image format derived from the Cineon format, used between film scanning, grading and film or digital-cinema output. | A container: the file can hold log or video-encoded values, and a header that is wrong or ignored is a common cause of a mis-set transform. |
| ARRI LogC3 with ARRI Wide Gamut 3 | ARRI | In use from 2011 | A scene-based logarithmic encoding in which the signal rises by a fixed amount for each stop of exposure; the C stands for Cineon. Footage looks flat and desaturated until a display transform is applied. | The curve's parameters vary with the camera's exposure index setting. |
| ARRI LogC4 with ARRI Wide Gamut 4 | ARRI | Specification dated 23 January 2025 | The successor to LogC3: a scene-referred logarithmic colour space made of the LogC4 curve and the ARRI Wide Gamut 4 primaries. | Not interchangeable with LogC3: a LogC3 lookup table applied to LogC4 footage is wrong. |
| Sony S-Log3 with S-Gamut3 or S-Gamut3.Cine | Sony | Current help guide, undated | A log curve for footage that will be graded, which Sony describes as closer to film in character than S-Log2; an 18 per cent grey is output at 41 per cent. S-Gamut3.Cine is the narrower, more practical of its two colour modes. | Taken from Sony's user guide; the technical summary that defines the curve could not be read. |
| RED Log3G10 with REDWideGamutRGB | RED Digital Cinema | White paper Rev C, 6 November 2017 | The single encoding RED's IPP2 pipeline develops raw footage into before grading; an output transform then maps it to an SDR or HDR display with highlight roll-off. | Only the pipeline note was read in full; no curve values are taken from the white paper. |
| Stop | Linear encoding | Even log share over 14 stops |
|---|---|---|
| 1st stop below clipping | 512 | 73 |
| 2nd stop below clipping | 256 | 73 |
| 4th stop below clipping | 64 | 73 |
| 6th stop below clipping | 16 | 73 |
| 8th stop below clipping | 4 | 73 |
| 10th stop below clipping | 1.00 | 73 |
| 12nd stop below clipping | 0.25 | 73 |
| 14th stop below clipping | 0.06 | 73 |
Why: Log footage was exported without a display transform, or with the transform bypassed on export.
Fix: Apply the camera maker's transform or a colour-managed output for the delivery standard, and check the export, not only the viewer.
Why: A transform for a different log curve or gamut was used, such as a LogC3 table on LogC4 footage.
Fix: Read the encoding and colour space from the clip metadata and match the transform to both.
Why: Log was recorded at 8 bits or heavily compressed, then stretched to display contrast.
Fix: Record log at 10 bits or more; where the material is 8-bit, grade gently and add fine grain before export.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
ARRI describes Log C as a scene-based logarithmic encoding in which the signal increases by a fixed amount for each stop of exposure, with the C referring to Cineon, and says the image looks flat and desaturated until it is tone-mapped and converted for a display.
Source: Log C (ARRI image science)
FactStrong evidence
Sony's guide states that with S-Log3 an 18 per cent reflectance grey is output at 41 per cent, and that the curve is intended for footage that will be graded after recording.
Caveat: From Sony's user guide; the document defining the curve's formula was not available.
Source: Help Guide for Creators: Setting basic contrast and colouring (Gamma / Color Mode)
Colourwise analysisStrong evidence
In a 10-bit linear file the brightest stop occupies about 512 code values and the tenth stop down about one, whereas an encoding that shared the codes equally over 14 stops would give each about 73.
Based on: Arithmetic by Colourwise: each stop is a halving of linear value, and 1,023 codes divided evenly by 14. An idealised pure-log curve, not any maker's actual one.
Caveat: Real log curves have a toe and do not allocate exactly equally; cameras also record with noise that makes the lowest stops unusable.
Source: Log C (ARRI image science)
ConventionModerate evidence
Productions monitor log recordings through a show lookup table, and that table can be designed to show an image darker than the exposure, as on House of the Dragon, where it displayed the picture one stop down.
Source: Crafting Legacy for House of the Dragon (Matt Mulcahey, American Cinematographer, 2 December 2022); Uncanny Valley: Blade Runner 2049 (Rachael Bosley, American Cinematographer, December 2017)
Reviewed 6 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.