Why does my camera underexpose snow?

Camera meters assume the scene averages to 18% middle grey. Snow is much brighter than middle grey, so the meter reduces exposure to bring it back to grey — resulting in underexposed, dingy-looking snow. Add +1 to +2 stops of exposure compensation to render snow as white.

When should I use spot metering?

Use spot metering when your subject is significantly brighter or darker than the background, such as a performer on a dark stage, a backlit portrait, or a bird against a bright sky. Spot metering reads only 2-5% of the frame, letting you meter precisely on your subject.

What is 18% grey and why does it matter?

All camera meters are calibrated to expose the scene as 18% grey (middle grey). This works for average scenes but fails for predominantly bright or dark subjects. Understanding this lets you predict when exposure compensation is needed.

How do I choose which parameter to compensate?

Adjust ISO if you want to keep aperture and shutter speed fixed (e.g. for consistent depth of field and motion blur). Adjust shutter speed if depth of field is more important. Adjust aperture if shutter speed must stay fixed (e.g. for motion blur control).

Metering Calculator — Exposure Compensation

Apply exposure compensation for tricky metering scenarios like snow, backlighting and dark subjects.

Aperture (f-number)

Current aperture

Shutter Speed (1/x)

e.g. 125 for 1/125s

ISO

Current ISO setting

Meter Mode

Metering mode in use

Scene Type

Compensation for scene type

How We Calculate This

Camera meters assume every scene averages to 18% grey. This calculator shows how to compensate when that assumption fails:

Exposure Compensation

Corrected ISO = base ISO / 2^(compensation)

Corrected shutter = base shutter / 2^(compensation)

Corrected aperture = base aperture x 2^(compensation/2)

Positive compensation brightens the image (for snow, white subjects). Negative compensation darkens it (for black subjects, low-key scenes). Each option maintains the other two exposure parameters.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.