Blend Median problem

Inspired by Pat David’s article [https://patdavid.net/2013/05/noise-removal-in-photos-with-median_6.html ] 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

2 Likes

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

2 Likes

@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)