Another OM-D trap to watch out for...

Started May 9, 2012 | Discussions thread
DjarumBlack
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Re: Another OM-D trap to watch out for...
In reply to NZ Scott, May 9, 2012

Olympus has a "Noise Reduction" setting in the camera. This is for most if not all PEN models. It has 3 settings: AUTO, ON, or OFF. This setting is for dark frame subtraction when doing long exposures.

In auto mode, I don't know when the camera decides to do dark frame subtraction. Check your setting and either set it ON for when doing long exposures (say over 2s) or AUTO.

Dark frame subtraction takes a picture of just black, in this case the back of the shutter. No light is let it. What happens in long exposure images is that as the sensor heats up during long exposures, dark current noise becomes part of the image. Dark current noise is noise generated by the electronics as they heat up. The good thing is that it has a fixed pattern. The camera does a difference between the dark frame and the original image to create a new JPEG.

I don't know if Olympus does this in RAW. My guess is not, so if doing RAW, one would need to create the dark frame seperately and subtract it out later.

NZ Scott wrote:

Louis_Dobson wrote:

Dark noise subtraction switches off in burst mode.

Or, to put it more simply, long exposures have to be in single shot mode or you will get horrid noise. Mildly annoying if you know, a disaster if you don't (ask me how I found out...).

Hi Louis,

Thanks for being honest about the camera. It's hard to sort out the fanboyism from the chaff sometimes.

I'm not sure exactly what you mean by "dark noise subtraction", but I can tell you that I get a tonne of noise when shooting long exposures with my E-P3. One thing I've found that helps a lot is exposing to the right as much as possible - basically, go as far right as you can without clipping highlights. This tends to reduce the amount of dark areas in the shot, and consequently also reduces the amount of noise.

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