Thank you for the reply, HarryT, Zeebra.
I updated the firmware on K4 but the result was the same.
It was very difficult but I tried to take pictures of both K3 and K4 with exactly the same settings.



The third picture is a bit too exaggerated(the upper is K4), to be honest.
But you can see the difference between the two.
I want to know if anyone has the same problem.
Because I am really thinking about contacting Amazon about this...