Blend Median problem

Inspired by Pat David’s article [ ] about “removing people”
I made five pictures with four chess pieces. The pictures I opened as a layers in Gimp 2.10-Ubuntu 18.04.

Filters> Gmic> Layers>Blend median gave me a sixth image where I hoped that only two of the pieces would be visible.
However, an attentive viewer easily sees that the others remain as ghosts. Using ImageMagick with the terminal command:
“convert *.jpg -evaluate-sequence median OUT.jpg” gave the same result.

Of course I did something wrong, but what?

Hej Alf!

Just a swift idea: might it be that your different shots vary in white balance and exposure?

Have fun!
Claes in Lund, Sweden


Yes, clearly, this is due to luminosity variations between all your images.
If you try to ‘normalize’ them a little bit, before applying the median blending, then it works quite well:

$ gmic *.jpeg balance_gamma , blend_median o output.jpg


@David_Tschumperle and @Claes

Many thanks for your help. It was wonderful that it was possible to fix.

The images were taken with a Nikon D7500, ISO 400, f / 9.0 1/4 sec. White balance auto. I saw for myself now that one picture was significantly darker than the others.

Alf (Norrköping)