How to photograph the northern lights
Every aurora guide gives one recipe — "f/2.8, ISO 1600, 15 seconds" — and every aurora is a different brightness. A faint grey arc needs fifteen seconds; a G4 curtain needs one and a half, and at fifteen it is a green smear. So this guide gives the rule that produces the number, ties it to the one live figure that tracks the display's brightness (NOAA's hemispheric power, in gigawatts), and hands you to the verdict page, which prints the current settings for your lens beside tonight's chance.
1. The exposure, from the aurora's brightness
The green line of oxygen at 557.7 nm has a surface brightness that varies more than a hundredfold between displays. The working scale below is a field heuristic — what aurora photographers use in practice, stated as such; NOAA publishes the power, not the exposures:
| Hemispheric power | What you see | Base exposure at f/2, ISO 3200 | At f/2.8, ISO 1600 |
|---|---|---|---|
| under 20 GW | a grey arc the camera finds before you do | 15 s | 30 s, the shutter ceiling (and it moves — accept the smear or stack) |
| 20–50 GW | grey-green, slow forms you can frame | 8 s | 30 s |
| 50–100 GW | colour by eye, forms move in seconds | 4 s | 15 s |
| over 100 GW | storm: fast curtains, rays, overhead | 1.5 s | 6 s |
Then the exposure law: time scales with the square of the f-number and inversely with ISO. f/2.8 needs twice what f/2 needs; ISO 1600 twice what ISO 3200 needs — four times in the right-hand column, capped at the 30 s a shutter dial ends at. That is the whole table above; the verdict page computes it live for whatever the oval is doing. Bright, fast aurora blurs at anything over about four seconds however you set it, so at 50 GW and up you open the aperture and raise ISO rather than lengthen the shutter.
2. Aperture: wide open, or one stop down
Aurora photography is starved of light; shoot the lens at its widest unless the corners smear badly (coma and astigmatism). A 14–24 mm at f/1.8–2.8 is the standard tool because the aurora is big: a curtain spans 60° of sky.
3. ISO: the sensor's clean ceiling
ISO 1600–6400 on any camera made since 2015. The noise you add at ISO 6400 is less than the smear you add at a doubled shutter, and stacking removes noise; nothing removes motion blur. Modern sensors are ISO-invariant above ~800, so underexposing at 3200 and lifting is the same as 6400.
4. Focus at infinity, by hand
Autofocus fails in the dark. Live view at 10× on a bright star (Capella, Vega) or a distant light; turn until it is smallest; tape the ring. Check again after an hour — cold lenses shift. A star that is a doughnut is out of focus; one that is a cross is fine.
5. White balance and RAW
Shoot RAW. Set white balance to 3 200–4 000 K so the green is green and the sky is blue-black rather than orange from distant towns; auto white balance will fight the green all night. Fix it later without cost in RAW.
6. The interval, for a sequence
Exposure plus two seconds, back to back, on an intervalometer: 8 s exposures every 10 s. A twenty-minute sequence is 120 frames, which is a timelapse, a stack, or the one frame where the curtain was best — you cannot know which while it happens. The planner turns the exposure into a full sequence with the card space it needs.
7. Where to point
Toward the magnetic pole, low, unless the display is overhead. The verdict page gives the bearing and the elevation of the brightest part of the oval from your pin; include ground — a tree, a lake, a person — because a sky-only aurora photograph has no scale.
8. Phones
A 2022-or-later phone in night mode with a 10–30 s exposure, on a rock or a tripod, records aurora you cannot see. It cannot do 1.5 s at f/2 for a storm — the phone chooses its own exposure — so for a G3+ night use the manual/pro mode if it has one, or accept the smear.
9. Cold
Batteries die at −20 °C; keep spares in an inside pocket and swap warm ones in. A lens brought from a warm car fogs instantly — leave it in the bag outside for ten minutes first, and put a hand warmer on the barrel for a long sequence.
10. After the night: the stack
A hundred frames of aurora are not a hundred chances; they are one integration. Drop the folder into the stacker: it aligns the sky, keeps every frame's aurora (a lighten blend on aurora frames is the "star trail" mode with the arc left in), removes the satellite streaks the intervalometer collected, and writes a 16-bit result. Or pick the single best frame with the review strip and stack the rest for the foreground. Nothing is uploaded.
Tonight's verdict and the live settings for this aurora → · The oval on the map → · Find a darker northern horizon →