OM1-MKII: The Long Exposure Noise Reduction

The longer the exposure, the warmer the sensor. The warmer the sensor, the noisier the photo. This is based on physics. There’s no way around it. You like it, you don’t like it, the longer the exposure, the noisier the photo will get. It’s mostly chroma noise (the red dots). This applies to all camera manufacturers: Canon, Nikon, Olympus, Pentax, Sony… So how do we get around it?

Most camera makers use the Long Exposure Noise Reduction. In the OM1-MKII it is:

Long Exposure Noise Reduction Options (Noise Reduction)

The way it works is the OM1-MKII takes a second exposure for exactly the same amount of time but with the shutter closed. Then it analyses the second exposure to find the chroma noise (the red dots) and remove it from the first exposure and write the file to the card.

 MENU ⇒ Shooting menu 1 ⇒ tab 3 ⇒ 3.ISO/Noise Reduction ⇒ Noise Reduction
  • Off: No noise reduction done.
  • On: Noise reduction is done at all shutter speeds.
  • Auto: Noise reduction is only done when the camera’s internal temperature is elevated.


  1. The long exposure noise reduction is activated when the sensor gets warm. When? That depends on the weather, the direction of wind… My experience, in my weather conditions, was around 4 seconds.
  2. In the MENU ⇒ Settings (cog wheel) ⇒ 3. Live View ⇒ Frame Rate » Normal to reduce the heat
  3. The long exposure noise reduction is done by taking a second photo with the shutter closed. The second exposure is the identical length of time as the first one.
  4. The CPU analyses the 2nd exposure against the 1st exposure and removes the chroma noise. This means that a 15 second exposure photo will be followed by a second 15 second exposure with the shutter closed making a total of 30 seconds.


  • Dealing with noise with this setting is the “old fashion way” of dealing with noise. Nowadays using denoising software does a better job. Be it Lightroom, BXO, Topaz…
  • Using High resolution mode will also reduce the both the luma noise (the little sand pebbles) and the chroma noise (the red and green small spots).