Cheap LED bulbs flood the room with light — but half the colours in the visible spectrum
may be missing entirely. A good LED fills in the gaps; a bad one doesn't, and your brain
pays the cost in eye strain, colour distortion, and disturbed sleep. Point your camera at
any light source and see what it's actually giving you.
The blue light spike in cheap LEDs disrupts melatonin production more than any other artificial light.
Most LED lighting peaks sharply at 450nm (deep blue) with a drop-off across the rest of the spectrum.
This blue spike suppresses melatonin by up to 85% compared to incandescent light, according to Harvard
Medical School research. A CRI (Colour Rendering Index) below 80 means 20%+ of colour information
is missing — red meat looks grey, human skin looks sickly, and the visual cortex works harder to
compensate, causing fatigue.
How to use this: Point the camera at any artificial light source — a ceiling LED,
a desk lamp, a TV backlight, an outdoor streetlight. The camera sensor acts as a crude spectrometer:
we analyse the RGB channel ratios to estimate colour temperature and quality. For best results, fill
the frame with the light source or a white surface lit by it.
—
estimated CRI · colour rendering index (0–100)
waiting for camera
—CCT (K)
—blue ratio %
—green ratio %
RGB channel spectrum
light type—
colour temperature—
CRI estimate—
blue spike risk—
sleep impact—
verdict—
▶ what is CRI and why does it matter?
CRI (Colour Rendering Index) measures how accurately a light source reproduces colours
compared to natural daylight. A CRI of 100 is perfect (sunlight); incandescent bulbs score ~100;
cheap LEDs often score 70–80. Below 80, colours look off — reds appear muted, skin tones look
washed out, and food looks less appetising.
The camera measures RGB ratios — a crude proxy for spectrum. Real CRI requires a spectrometer.
But the RGB ratios reliably indicate:
Colour temperature: warm (2700K–3000K) vs neutral (4000K) vs cool (5000K+)
Blue/green dominance: high blue = cheap LED or "daylight" bias
Red deficiency: low red channel = poor CRI, suppressed melatonin
Note: your phone camera applies auto white balance, which partially corrects colour temperature.
Disable AWB if you can (camera apps) or hold the camera near the light source for a raw reading.