Darker area in all (very)underexposed pictures

Hi,
I'm trying to make some astrophotography with my nx300 but when the shutter speed is
very low (5 s and above), in every underexposed picture I see a darker area on the left of the images.
The lens is not the cause (I made pictures without lens and the result is the same).
I would like your opinion about this problem.
Thank you.

Stars (Shutter speed 8s , iso 25600, f/4.5  ,35mm,  15 stacked images)

Are you incorporating "darks" and "flats" and whatever which are designed to help compensate for sensor anomalies?

Assuming of course there's not a clump of fluff floating around in front of the sensor

Stefano A wrote:

The irony is that in the darker zone seems that there's less noise.

One might almost imply that there's an area of reduced sensitivity within the sensor, but I know just enough about sensors to recognise that as a very unlikely situation

It'd be interesting to see the results from another camera of the same model. I wouldn't expect the fault to be in the same place, but there might be an indication of a wider-spread issue.

Hopefully someone else with an NX300 will read this and make a hi-ISO 30sec exposure with the lens cap on for comparison.

Good luck.

Stefano A wrote:

Indeed It would be interesting to see another nx300, 30 s , high ISO "black" photo.

Your Samsung camera at 25600 ISO, 30s, have a uniform noise pattern in a black photo?

My NX5 only goes to 3200 ISO, but it is uniformly noisy at that setting with a 30sec exposure.

NX5 - 3200ISO @ 30sec (with lens cap on) - result enhanced to emphasise background noise.

Stefano A wrote:

Indeed It would be interesting to see another nx300, 30 s , high ISO "black" photo.

Your Samsung camera at 25600 ISO, 30s, have a uniform noise pattern in a black photo?

If of any help, these are from a JPG taken just now with my NX300 - one simply resized, the other after some overall exposure uplift in LR.... high ISO, 30 secs exposure, 30mm lens at smallest aperture in "A" mode, with the lens cap on and manual focus, and very probably with long exposure NR applied by the camera.

Hope it's what you wanted!

I'm sure I've stood on a carpet much like this!

Some slight differences perhaps, but - to me - the exposure looks fairly even across the frame?

Peter

I'd forgotten what a nice little camera that is!

For me, the lens range just needed a lightweight, modestly good OIS telezoom, of around 40-100mm (equiv to, say, 60-150) and f/3.5-5.6, to accompany the kit PZ and pancakes - and I'd probably not have gone over to M43.

Shame....

Peter