using slider for pictures – quality is horrible

Hi Kriesi team,

I`d like to use the simple slider – but the compression of pictures is really bad.
If I set the slider to the size of 260*185 px, the pictures are compressed by the slider or whatever.

If I show pictures, I need them (only reduced for mobile devices) in this quality, I uploaded them.
I do not like any compression!

First I uploaded the size, I need for the slider size, I took (260*185px) – do not work
2nd I uploaded a picture with size of 3000px width, 96% of quality, 72dpi -> result is not usable.

What I think is usfull, is the regular Upload box. Regular I can set on the right, what size of the picture I need. If I upload pitures with the small slider, I can only choose the picture, but nothing more.
Otherwise I need a control for pictures into the slider. I need the funktion to say “show original size” (without compression)

Have a look please:

here is my playground is attached
http://www.der-eventfotograf.de/dereventfotograf

first picture into slider on the left (musicans) -> picture in original I uploaded was 260*185px
second picture (Person with heart) -> picture was 3000px width

both pictures are compressed by the slider –
as photographer I need the control about the picture quality :-)

thx Andreas