long exposure noise reduction issue (X-T100)

What's going on here?

Long Exposure Noise Reduction (LENR) turned off:

Crop of upper-left corner:

LENR turned on:

As you can see, the image with LENR turned on looks redder, noisier, and more sharpened (over-sharpened).

Of course, I appreciate that the hot pixels have been removed, but why are these negative side effects happening? And is there any way to avoid these artifacts in-camera while keeping LENR turned on?

I've never experienced this issue on my Nikon cameras or Sony camera when doing night photography. I love the X-T100 otherwise.

All of the above images were shot on a tripod, in JPG, and are straight out of camera.

Any clue what's going on here? And have you ever seen this before on any camera?

Did you take the NR On shots second? Could be the sensor heated up more and became noisier.

Erik Baumgartner wrote:

Did you take the NR On shots second?

Yes, it was the very next shot.

Could be the sensor heated up more and became noisier.

Interesting theory. I'll have to check to see if subsequent photos that night get progressively redder/noisier/more sharpened.

sluggy_warrior wrote:

KneeConWon wrote:

Erik Baumgartner wrote:

Could be the sensor heated up more and became noisier.

Interesting theory. I'll have to check to see if subsequent photos that night get progressively redder/noisier/more sharpened.

One way around it might be taking multiple short images, e.g. 5-second shot then pause for a second, median blending them in post. The sensor gets a bit of break in between, might help?

Thanks for the suggestion! I'll definitely try giving the camera a break between long exposures and see whether that helps the issue.