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Filmmaking Dictionary: Number 7 / 7.5 IRE Setup
Definition
7.5 IRE setup is the black-level offset associated with certain analogue NTSC video systems, notably historical North American composite video practice. In that context, picture black sits at 7.5 IRE above the blanking reference, while nominal reference white is at 100 IRE.
This is a signal-format convention, not a universal creative instruction to lift every image’s blacks. Other analogue systems and digital video workflows use different relationships. Applying the wrong setup can make an image look washed out or crush shadow information.
Analogue Setup Versus Digital Black
Digital video does not generally require adding the historical 7.5 IRE analogue pedestal to the picture. In a common limited-range eight-bit luma representation, nominal black is code value 16. A correctly configured waveform can display that digital black at 0 IRE.
Full-range and limited-range digital signals also need correct interpretation. That issue is separate from the analogue NTSC setup convention, even though both can produce visibly raised or crushed blacks when handled incorrectly.
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Where the Term Still Matters
- Digitizing legacy analogue NTSC recordings.
- Configuring older playback decks or analogue output converters.
- Checking a transfer chain with appropriate test signals.
- Interpreting technical notes on archival material and older broadcast equipment.
Practical Transfer Example
An archive transfer looks grey in the shadows because the deck’s analogue output and the capture device’s expected setup do not match. Correcting the transfer settings is preferable to casually dragging every clip’s black level down in the edit. The original signal path should be understood before applying a compensating grade.
Use the equipment documentation and appropriate test material to establish what is being supplied and recorded. A scene containing no true black reference cannot, by itself, prove that the transfer is wrong. Intentional low contrast and a technical level mismatch are different possibilities.
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Frequently Asked Questions
Should HD or UHD masters have blacks raised to 7.5 IRE?
Not as a general rule. Follow the delivery’s digital level and colour specifications rather than importing an analogue NTSC convention.
Is IRE a percentage of scene brightness?
No. It is a video-signal measurement scale. Its meaning depends on the signal and display configuration, not a direct percentage of the light falling on the set.
Related Terms
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