Low-Light ISO Calculator
Calculate the required ISO for proper exposure in low-light conditions
Photography
Low Light
Night
About Low-Light ISO Calculator
This calculator uses the formula: ISO ≈ (N² / t) / 2^EV × 100, where N is the aperture f-number, t is the shutter speed in seconds, and EV is the exposure value.
When shooting in low light, balance your settings using the Exposure Triangle Calculator to find the best combination of ISO, aperture, and shutter speed.
For handheld shooting, check the Handheld Shutter Speed Calculator to avoid motion blur.
All calculations are performed locally in your browser. No data is sent to any server.
Frequently Asked Questions (FAQ)
How is ISO calculated for low light?
The formula is ISO ≈ (N² / t) / 2^EV × 100, where N is the aperture f-number, t is shutter speed in seconds, and EV is the exposure value of the scene. This gives you the ISO needed for proper exposure.
How do I know the EV of my scene?
Use a light meter app on your smartphone, or estimate based on common lighting conditions. Bright sunlight is around EV 15, indoor lighting is typically EV 4-7, and night scenes can be EV 0 or lower.
What ISO should I avoid to prevent noise?
This depends on your camera. Modern full-frame cameras handle ISO 6400+ well, while older or smaller sensors may show noise above ISO 800-1600. When possible, use wider apertures or slower shutter speeds instead of higher ISO.
Should I use Auto ISO?
Auto ISO can be helpful but set a maximum limit. Knowing the calculated ISO helps you decide when to use a tripod, wider aperture, or add light. Use our Handheld Shutter Speed Calculator to find your minimum shutter speed.
How can I reduce the required ISO?
Use a wider aperture (lower f-number), slower shutter speed (with tripod if needed), or add light to the scene. Check our Exposure Triangle Calculator for equivalent exposure settings.