The longer the exposure, 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 it will get. This applies to all camera manufacturers: Canon, Nikon, Olympus, Pentax, Sony… So how do we get around it?
Canon, has a method to finding the noise and then removing it from the photo. In the Canon 7D’s case it is:
C.Fn II -1: Long exposure noise reduction
- 0 — Off: disabled. You will either live with the noise or use some external software like Nik Software DFine.
- 1 — Automatic: The noise reduction will kick in only when the shutter speed is greater than 1 second and if the noise detected is typical of long exposures.
- 2 — On: The noise reduction will kick in every time the shutter speed is greater than 1 second even if the noise typical of long exposures is NOT detected.
- The long exposure noise reduction is only activated at shutter speeds that are 1 second or longer.
- 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.
- The CPU analyses the 2nd exposure against the 1st exposure and removes the noise. This means that a 15 second exposure photo will be followed by a 2nd 15 second exposure with the shutter closed making a total of 30 seconds.
- You will need to experiment with the setting of 1 or 2. It’s not: I prefer the automatic vs the always on. Different conditions will give different results, depending on the exposure, the shadows, the light or the lack of light.
- You should disable the setting if you are using “heavy” neutral density filters like 10d to give you very long exposures.