Step 5: Useless Pixels

Zero-variance features

1 ExplorePlay below
2 ReadUnderstand
3 BuildHands-on lab
4 CompareSolution
💡 ReflectThink deeper

Find the useless pixels

Some pixels never change across all 1,797 samples — they carry zero information. Drag the slider to set a minimum variance threshold and watch useless pixels disappear.

1.0
Pixel variance (std dev)
Useful pixels
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Think Deeper

In the Explore tab, drag the variance slider to max. How many pixels survive? Could a model still work with just those?

At high thresholds, only ~10-15 center pixels remain — and yes, a model can still classify reasonably well. This is dimensionality reduction: fewer features can mean faster training and less overfitting.
Cybersecurity tie-in: In security logs, this is equivalent to a field that's always empty — like a TTL column that's always 64, or a protocol field that's always TCP. Removing useless features makes models faster and often more accurate.

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