Why is Siril reading the file size incorrectly?

My Canon 90D CR3 files are 6960x4640pixels but Siril reads them as 6984x4660.

  1. Why is this?
  2. Is this causing the stacking error?
  3. Why didn’t the program convert the Light Raw files to FIT before the error?
    TIA for your help!

Siril does not read the size incorrectly at all.
It uses LibRaw to read files. LibRaw tries to extract as much image as possible, so ‘match with other apps’ is not default.
It is therefore imperative to convert the files using the same software, in this case Siril. Otherwise, sizes may differ by just a few pixels.

Thnx for your response, it seems like I should disregard the file size difference. I’m still confused why the process failed. The Bias, Flat, and Darks all converted from RAW to FIT but the Lights didn’t. All files are the same size, any ideas why the stacking failed?

You said you did not obtain the lights in the same way you did the Bias, flat darks. So that could be the issue.
Please, have a look here: Calibration — Siril 1.2.0 documentation

Thnx for your input. The Lights, Darks, Bias, Flats were all taken at the same temp, ISO, file size, with the same sensor and optics. I’m going to move my questions over to the FB group for clear answers.

Is this with same capture software???

I’m the administrator of the FB group.