Strange long exposure issue

[soko]

I was taking some long exposure shots last night and noticed when I used my Panasonic 20mm with the OM-D there were these random coloured pixels scattered throughout the image, for example like this: http://i.imgur.com/RE4qIoq.jpg

Only happens when I use that lens, I hope its not broken ? :S

 

[soko]

By the way I'm referring to the pixels in the darker areas, ignore the light trail in the middle of the picture, thats an aeroplane.

 

[KVG]

I had the same issue with my 20mm and 14mm where I would get red spots in dark areas and random white pixels that look like stars.

 

[FrayAdjacent]

I see a few blue and a couple red spots in the ground area of the picture... I'd suspect some weird flare issue due to the lights. Does it happen if there are no sources of light directly in the frame? Are you using a hood to limit the possibility of light sources hitting the lens from outside of the frame?

 

[soko]

I see a few blue and a couple red spots in the ground area of the picture... I'd suspect some weird flare issue due to the lights. Does it happen if there are no sources of light directly in the frame? Are you using a hood to limit the possibility of light sources hitting the lens from outside of the frame?

Only happens in the long exposure shots at night, other shots are fine, no hood used.

 

[entropicremnants]

You need to turn long exposure noise reduction on. This is NOT filtering -- it's a common technique used in digital astro photography and won't degrade you image. Google "dark frame subtraction" to understand it.

On your E-M5 it's here: Gear Menu --> G (Color/WB) --> Noise Reduct.

Set it to AUTO or ON. I do a lot of long exposures doing urbex in dark buildings and I leave it in AUTO on my E-M5.

Again I repeat: this is NOT noise filtering and doesn't hurt your images. It subtracts out hot pixels which is what you are seeing.

 

[RnR]

You should write an FAQ post on these forums entro. Seems this issue comes up often enough

 

[remoteman45]

Would you leave it on for shooting star trails with an intervalometer as well?

 

[FrayAdjacent]

IIRC, enabling the noise reduction will add your shutter speed to the exposure processing. Basically it takes the shot, then records what the sensor sees with the shutter closed for the same amount of time, then subtracts the hot pixels from the image.

A 30 sec exposure will be followed by a 30 sec pause as it does a closed exposure to map the hot spots.

 

[entropicremnants]

Would you leave it on for shooting star trails with an intervalometer as well?

As long as the doubled exposure times don't take you over the interval time, then yes if you want clean images.

 

[RobWatson]

I can tell you that building dark frames and manually correcting in post does not work as well as the in camera correction. It does work but just not quite as well. If one is pressed for time then a manual correction in post is possible.

It is not a hard test to perform so one can prove it to themselves if needed.

 

[homerusan]

i had similar issue here
https://www.mu-43.com/f42/sensor-problem-43239/
every cmos sensor has this kind of problem after it gets hot.
its not a big deal