How to expose correctly using the Atomos Shogun – Rec. 709

In this lesson we’ll learn how to expose Rec. 709 in Rec. 709 color space using the Atomos Shogun.

The test is similar to what I used to explain the Picture profile modes, and I’ll be using a DSC Labs OneShot as reference. The lighting is pure halogen, custom white balanced at 2900K. The light is from the left that is why there is a small but negligible fall-off (the real world barely has zero fall-off).

The spot meter in the camera was measured within the large grey patch for exposure. Exposure settings are available in the first image.

Here are the results (click to enlarge):

Rec709

The last three images underneath the yellow line are of the same scene underexposed by 1/3rd of a stop. I’ll explain why.

  • The waveform tells us middle grey falls on 60 IRE, where it should be lower.
  • The Zebra at 50 should show up on the grey patch, but it doesn’t.
  • The false color tool should be showing green on the grey patch, but it doesn’t.
  • This means the image is slightly overexposed.

By underexposing the image by 1/3rd of a stop, I was able to bring everything into the expected zones. The false color is green, the zebra shows up and the waveform tells us the middle grey patch is at about 45-50 IRE. White is at about 85 IRE, which is fine.

This is not a significant error, as a 1/3rd of a stop is perfectly acceptable either way. It could be the mistake of the spot meter, or of the aperture in the lens, etc. Bottom line is, it works fine.

How to expose for Rec. 709 using the Atomos Shogun

Here’s the easy way:

  1. Keep middle-grey at about 45-50 IRE, and keep your white always below 90 IRE for studio swing (this is the broadcast standard)
  2. Make sure the RGB parade lines up – this is a quick indicator of white balance issues. You can use the vectorscope as well, but you need a clean patch to study and that’s not always practical.
  3. If using the false color, middle grey should be at green, and Caucasian skin should be pink. In fact, the sweet spot is between the grays (24 IRE to 77 IRE).
  4. The Zebra is not very useful because it starts at 50 IRE and this includes the region from 47-54 IRE. It misses the green zone, so don’t use it for middle grey. Use it only to check for blown highlights, where it should be at 90 IRE.

Click on the link below to the next lesson or head over to the main menu (above). If you need help with something, feel free to send me an email. I’ll try to get back to you as soon as possible.