Long Exposure Noise Reduction Time Calculator

Long Exposure Noise Reduction (LENR) is an in-camera feature that reduces hot pixels and thermal noise in exposures typically longer than 1 second.

How it works: When LENR is enabled, the camera takes two exposures:

1. The actual photo — the exposure you set (e.g. 30 seconds)
2. A dark frame — a second exposure of equal length with the shutter closed

The camera then subtracts the dark frame from the actual photo. Since both exposures share the same sensor temperature, the thermal noise pattern is nearly identical and cancels out almost completely.

Total time formula: Total time = Shutter Speed × 2 + processing buffer (~2–5 seconds)

Example:

• Shutter speed: 4 minutes (240 seconds)
• Dark frame: 4 minutes (240 seconds)
• Processing: ~3 seconds
• Total: ~8 minutes 3 seconds

When LENR makes a visible difference:

• Exposures of 30 seconds or longer
• High ISO settings (ISO 800+) combined with long shutter
• Warm ambient temperatures (heat increases sensor noise)
• Night sky and astrophotography where stars would show “hot pixels”

When to skip LENR:

• Star trail photography — you cannot shoot multiple frames back-to-back with LENR on without losing time between frames
• Time-lapse sequences — LENR doubles the interval and causes gaps
• When you prefer to handle noise in post-processing (e.g., using Lightroom’s Denoise AI or stacking multiple exposures)

Alternative to LENR for astrophotography: Stack multiple shorter exposures instead of one long exposure. This approach averages out random noise while preserving signal, and lets you continue capturing frames without waiting for dark frames. Most astrophotography software (Sequator, DeepSkyStacker, Astro Pixel Processor) handles stacking automatically.

Practical tip: Charge your battery fully before a long session with LENR enabled. A 4-hour shoot effectively becomes 4 hours of the sensor running at full power continuously, which significantly increases battery drain.