Maintain image aspect ratio in carousel

The issue lays here, on bootstrap CSS:

img {
  max-width: 100%;
  width: auto   9;
  height: auto;
  vertical-align: middle;
  border: 0;
  -ms-interpolation-mode: bicubic;
}

Having set max-width: 100%; the image won’t be any larger than the viewport. You need to override that behavior on your CSS:

.carousel img {
  position: absolute;
  top: 0;
  left: 0;
  min-width: 100%;
  height: 500px;
  max-width: none;
}

Note the max-width: none; added at the bottom. This is the default max-width value and unsets the limit.

Here’s your fiddle updated.