Reading Light

Photography Fundamentals

Course 1 · Chapter 4 · Reading Light: Golden Hour and Colour Temperature

Light Is the Subject

Photography Fundamentals 1 to 3 dealt with how a camera records light. This chapter is about the light itself: when it is soft or harsh, warm or cool. The same scene can look completely different an hour apart.

Golden Hour

Wikipedia's Golden hour article describes it as the daytime period shortly after sunrise or before sunset, when daylight is redder and softer than when the sun is high. Photographers and cinematographers often call it the magic hour, though some cinematographers use "magic hour" for the time between sunset and nightfall when there is no direct sunlight.

Definition of golden hour	Sun elevation
One group of sources	0 to 6 degrees, or 0 to 10 degrees, above the horizon
Another	4 degrees below to 6 degrees above
timeanddate.com (as cited by the article)	6 degrees below to 6 degrees above

The article gives three different definitions, so there is no single agreed answer. I have listed them side by side rather than choosing one.

Why the light looks the way it does

At a low angle the sunlight passes through more atmosphere. According to the article, this weakens direct light, so more illumination comes from the sky; contrast drops, shadows are less dark, and highlights are less likely to overexpose. More blue light is scattered, so the sunlight looks redder. Shadows are longer. Warm, diffuse light tends to suit landscapes and portraits.

Blue hour

The blue hour comes just before golden hour at sunrise or just after it at sunset. The sun is below the horizon, roughly 3 to 10 degrees depending on the definition, the indirect sky light looks mostly blue and shadows are soft.

The "hour" is not an hour

The article says the period has no fixed length. It depends on season and latitude. Near the equator the sun climbs quickly and the period is under an hour; farther away it can last more than an hour, and at high latitudes in some seasons the sun may never reach 10 degrees, so golden hour can last all day. Check a sunrise and sunset table for your own location rather than assuming 60 minutes.

Colour Temperature

Colour temperature describes the colour of a light source by comparing it to an idealised black body, and is conventionally expressed in kelvins (K). The Color temperature article gives these example values:

Source	Colour temperature
Candle flame	1,850 K
Sunrise/sunset	1,850 K
Standard incandescent lamp	2,400 K
Horizon daylight	5,000 K
Vertical daylight	5,500 to 6,000 K
Overcast sky	6,500 K

The Golden hour article gives somewhat different figures: about 2,000 K shortly after sunrise or before sunset, about 3,500 K during golden hour and about 5,500 K at midday, and says altitude, latitude, season and weather shift them. The two pages do not agree exactly on sunrise and sunset (1,850 K against about 2,000 K), and I did not find out why (check).

Warm and cool run the wrong way round

In artistic colour theory, colours over 5,000 K are called "cool" and 2,700 to 3,000 K "warm". The article says this is exactly the opposite of black-body radiation, where hotter objects glow bluer. So "warm light" means a low kelvin number.

The script below sorts the example values and labels them with a simple rule of my own (3,000 K or lower counts as warm-looking, 5,000 K or higher as cool-looking, anything between as in between). The article only names 2,700 to 3,000 K warm and above 5,000 K cool, so the in-between rule is a simplification (check). I ran it and the output is shown.

sources = {
    "Candle flame": 1850,
    "Sunrise/sunset": 1850,
    "Golden hour (typical)": 3500,
    "Standard incandescent lamp": 2400,
    "Midday sun (typical)": 5500,
    "Overcast sky": 6500,
}

def label(k):
    if k <= 3000:
        return "warm-looking"
    if k >= 5000:
        return "cool-looking"
    return "in between"

for name, k in sorted(sources.items(), key=lambda kv: kv[1]):
    print(f"{k:>5} K  {label(k):<13} {name}")

# Output
K  warm-looking  Candle flame
K  warm-looking  Sunrise/sunset
K  warm-looking  Standard incandescent lamp
K  in between    Golden hour (typical)
K  cool-looking  Midday sun (typical)
K  cool-looking  Overcast sky

What to take from it

The sun gets cooler-looking as it climbs, from about 1,850 to 3,500 K near the horizon to 5,500 K at midday, and an overcast sky is cooler still. Chapter 7 returns to this, because a camera has to be told which light it is looking at (white balance, check).

Not Yet Verified, and Sources

Sources. Wikipedia articles Golden hour (photography) and Color temperature, both read through page summaries. The Color temperature page text is 134,346 characters and only the first 100,000 were covered.
Conflict not resolved. Sunrise and sunset colour temperature differs between the two pages (1,850 K and about 2,000 K).
Not checked. Midday daylight is not listed directly in the Color temperature table I saw; 5,500 K comes from the Golden hour page. The simplified warm/cool rule in the script is mine.

Exercises

Exercise 1

Look up sunrise and sunset times for your own location on one day in summer and one in winter. Estimate how long the sun spends below 6 degrees of elevation after sunrise, using whatever source you like, and say whether "golden hour" is longer in one season. Write down your source.

→ Solution

Exercise 2

Add three more sources of your own to the script (for example a cloudy day or a phone torch), looking up each kelvin value from a named source, and rerun it. Say which label each one gets and whether the label matches the article's warm and cool definition.

→ Solution

Exercise 3

Explain in three sentences why a photograph taken at 3,500 K golden-hour light looks warm even though 3,500 K is a higher number than a candle's 1,850 K. Use the "warm and cool run the wrong way round" box in your answer.

→ Solution

Quick Reference

Golden hour: redder, softer light after sunrise or before sunset; defined variously as up to 6 or 10 degrees elevation
Blue hour: sun roughly 3 to 10 degrees below the horizon
Colour temperature: kelvins; warm-looking is low, cool-looking is high
Examples: candle 1,850 K, midday about 5,500 K, overcast 6,500 K
Check: sunrise figure conflict, the in-between rule

Coming next

Photography Fundamentals 5 covers composition: how to arrange what is in the frame.