Need a tip: Picture in K2 Article/image is murky

I know it's just me doing somethign wrong, but for some reason here: http://v-boge.org/blog/item/3425-ostav-eto-pozadi-sebya-chast-1 the picture is of REALLLLLLY bad quality. I've been fiddling around with all settings. Can't find the one that will put better quality picture there.
Would you, please hint me as to which setting makes good quality picture like here: http://demo.gavick.com/joomla25/msocial/index.php/k2/k2-item
The picutre in original is of good resolution - it's site getting me a wrong thumbnail...

Hi,
some facts:
this image has 100px × 75px (but was rescaled to 728px × 546px) - it means mechanical rescale - poor quality!
This image K2 size is "L" ,
I suggest to check settings of this category
and
also general settings K2 options

This image K2 size is "L" ,
I suggest to check settings of this category
and
also general settings K2 options

Here's what is set in k2 options: https://yadi.sk/i/VCG63Mq4bwh4X and settings for category are simply copied from QuickStart pack for Msocial. That's why I am asking for help - can't find where else it's twisted...

and what you have in this K2 Category - in settings, maybe there is ...
or you can add manually 730px for (L)arge - I guess.

and what you have in this K2 Category - in settings, maybe there is ...
or you can add manually 730px for (L)arge - I guess.

Thanks, found it - it has cascading inherited settings and one of categories had this 100px size limit set. Thanks.

Yes, sometimes in K2 it's "hidden" and hard to find for first time.