How to set the exposure relative to another image?

Software darktable
1

DT 3.8.1 in debian 11

I have 128 images done every 30 seconds of a bridge at sunset. I have sliced and reassembled them but it doesn’t work as I wanted. I wanted some much smoother transitions.

Here, I have made a simpler variation with only 26 slices and resized to 1500px as it’s easier to see:

26-sliced-resized-25
26-sliced-resized-251502×1005 332 KB

The camera settings were fixed iso, fixed aperture, fixed focus and a good tripod but the shutter speed varied as it got darker and darker.

How can I change the exposure relative to the previous image, so I can have a 4 or 5 ev range from the first/left to the last/right? or do I have have to that manually.

The problem with manually is that I plan/hope to get to 1000+ images every 10 seconds.

Thanks

2

I don’t think this is possible inside darktable. There was a time lapse script for DT, but I don’t know that its been updated for 3.8

3

such relative exposure feature was merged into master today:

  • in source image: exposure module: switch mode to measure then select reference area
  • in target image: exposure module: switch mode to correction then select area to match exposure in source

There’s a similar feature for colorcalibration in work …

6 Likes
4

Merged also just an hour or so after the exposure mapping.

4 Likes
5

yep, found it …

6

Looking forward to the result. Hopefully you will post it in thr form.

7

Aurelian made a video about it some time ago…Check his YouTube channel …

8

That means that the shooting duration is close to 3 h, with big change of lightness
Your intent is to shoot some Time Slice Photography. So the approach is very close to timelapse process. Maybe see https://pypi.org/project/dtlapse/#introduction but it works only with dt 3.0.2

9

I tried the link dtlapse and it didn’t work. I have found:

https://pypi.org/project/dtlapse/

It’s going through the xmps. I can do almost the same with sed (on linux) without the plot. That’s an interesting idea.

Thanks

10

Have you noticed or followed this?? Could be something in here of use??

11

No I haven’t look at this but it seems interesting, I’m not doing video, eventually it becomes just 1 image.

Meanwhile I’m exploring/doing it in GIMP (and learning GIMP) and varying the masks.

Thanks,

1 Like
12

Ya I only took a quick look…thought there might be some exposure magic or something else useful there. The same project might have some timelapse photography features as well . I would have to dig deeper…