If I scale down an image with showfoto or krita I obtain a blurry image. Doing the same with gwenview work as expected.
I've searched through all menus but cannot find how to proper do it with those programs. It seems that the scale function work for scaled up images, but if you want to reduce the number of pixels they do strange things.

This sounds like a bug. Can you please report it at bugs.kde.org?

I did some scaling down with krita but the result looked normal to me, this is with trunk.

can you post the image/screenshots for compare?

OK, nothing to worry about, sorry... I had another problem (which I'll report on another thread), restarted the krita config file and now seems to work. Regarding Showfoto (version 1.0.0), the "problem" is only with the preview: when I choose the new size the preview is terrible, but if I accept that terrible image I obtain a good one...