WHY DO FILMMAKERS PREFER RECORDING IN LOG?
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WHY DO FILMMAKERS PREFER RECORDING IN LOG?

September 13, 2022
  • Vasudev Vashisht
  • Cinematography, Useful Tips, Color grading

Nowadays, digital cameras offer a variety of shooting options in terms of formats and outputs of video. These can often make one lose track of what approach is best suited for a project and what effect a particular setting can have on the final image. What is the Log video format? What is RAW footage? Are RAW and Log the same?

Let’s quickly dive into these terms and ultimately understand why & when filmmakers prefer recording in Log & RAW.

Why Log?

Log is tailored to make very flat footage (desaturated and low contrast) that gives us the maximum amount of information from the film stored in video format. The wide tone area captured via Log format is effective when shooting subjects that might experience loss of details in darker shadows or overblown highlights. Recorded Log footage looks dull and blown out, but when processed (color corrected and color graded) in post-production helps in preserving details.

Different companies use different algorithms, the Log is short for Logarithmic, to create their Log files and thus name them with different starting letters: Sony calls theirs S-Log, RED log is for RED cameras, V-Log is Panasonic, Arri uses Log-C, Nikon N-log, while Canon uses a C-Log.

Log and Linear color spaces

In any color curve, the blacks and shadows are represented in the bottom left and as you move to the top right, you have the whites and highlights. A log curve, basically, pulls the dark parts of the image upwards, hence retaining the shadows. The top of the curve is flattened, or pushed downwards, therefore retaining highlights in the same color range. Hence, you end up retaining more data from either side of the curve.

In essence, log helps you to capture highlights, whites, shadows, and blacks, with the highest range of precision by getting the most out of the camera’s sensor and dynamic range.

Although it’s still a compressed video format, and certain elements are present in the footage, it’s still really flat footage, much better than Rec. 709 (Linear color space) with tons of information.


Log v/s Rec. 709

Digital cameras are generally set up to shoot in Rec. 709. Rec.709 is the standard color space used by TVs and monitors worldwide. It is quite realistic, has a decent amount of contrast and saturation, has colors baked into the image, and thus offers less flexibility in post-processing. Log gives us more room for color alteration, but since Rec. 709 is the standard space, one usually applies Rec. 709 LUTs, to be able to get that color space on Log footage in post. On the set too, LUTs can be applied so that the monitor shows desirable colors and does not output gray unsaturated tones. Log preserves more details in highlights and in shadows, it offers a wider dynamic range to play around with, and in fact, gives more freedom to fine-tune the colors in post-production.

Log footage and Log with Rec. 709 LUT

What is RAW footage?

RAW is not a video but is a collection of the ‘raw’ data that needs to be converted to video format later. Think of it as the negative in film photography, while it does contain all of the necessary information to ‘develop’ the final image, it is not the desired straight out of the camera image. RAW is not an acronym, but a shorthand for camera raw information.

When editing RAW footage, you can basically change each and every aspect of the video. Changes in ISO, white balance, etc. can be made. You can tweak the way the video was shot. RAW files are hefty in size, and extremely heavy to work with.

RAW takes the data from the photosites on the sensor and records all of it before the camera initiates any conversion to video format. Every possible camera out there has a RAW step in the image-capturing process, but only some cameras allow us to tap into the steps and record that RAW data (ARRI Alexa, Blackmagic
URSA Mini Pro 12K, etc.)

Log v/s RAW

Raw is not Log, since Log is a video format, and RAW is not video. RAW data has no video processing injected into it and has to be converted into a video for viewing. Log is a video and has things like white balance baked into it. They’re very much not the same; however, they’re both designed to get the most information out of the sensor. Raw is getting everything the sensor has to offer; likewise, Log curves are designed to get the most tonal range out of the sensor.

Log is still a video format, so unlike shooting RAW, it can be directly seen on an external monitor without a conversion step. Simply, the biggest differences between Log and RAW are to do with storage space and white balance. RAW files are huge but are the best imagery possibly extracted from any camera.

Shooting RAW allows for the flexibility of a total change of white balance in post-production. Log does not.

As long as you manage to always shoot at the correct white balance, Log is a perfectly viable option, much handier than RAW since it uses less space

Conclusion

If you want the footage to be realistic and in alignment with what our eyes see, or don’t wish to color grade the video afterward, because of the shortage of time, you better use Rec709 as it looks good enough.

If you want more room to add colors and contrast, and color grade the video better, it’s good to use Log format and if you want the most out of the sensor with the freedom to tweak the footage the way you want, RAW will always be the best choice.

Tags

Cinematography, Useful Tips, Color grading.

Written by: Vasudev Vashisht

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