Have I broken the theme and or slider?

I’m puzzled by something.

I have an image in the slider I resized to 1140×500 that looks great. Everytime I add another pic with the exact same specs something weird happens.

The pic loads with the specs of 1140×500 then quickly appears to break and/or resizes itself so that it has a large white space at the bottom half of the image. This creates a large white space between the slider and the thumbnails on the homepage.

Should I make the images smaller and resize using CSS to create the illusion of the size I want?

Thanks