[Gimp-user] grainy scanned images

[Olivier <olecarme gmail com>]

I'm  using GIMP 2.9 on Ubuntu Studio with MATE window manager. I'm
scanning black-and-white photos taken slightly less than 50 years ago.
This is working generally well, although of course I have to rotate,
crop, and sharpen the images, and use the Levels tool a lot. However,
for two photos a weird thing happens: the photo looks rather good when
displayed in the GIMP window, but it looks terribly grainy when
displayed by "Eye of MATE Image Viewer".

I placed the photo at the address http://olecarme.homelinux.net/page0022.jpg

Clearly it's grainy, but not so much as in the image viewer, and in
the GIMP window it looks acceptable at a scale of 33.33%, and even at
a scale of 50%.

Two questions:
- May anybody provide an explanation of this phenomenon?
- Is there a way to display the image correctly outside of GIMP?

Thanks for any idea!

Olivier Lecarme