slideshow-gallery & iPhone

I am building a website with slideshow-gallery installed.

The problem is, i am using the slideshow-gallery as a header image which flicks through a few images. When i view the site on an iPhone the images are very distorted, the width is ok because i have altered the CSS to use 100% width, but the height distorts the image because it is manually coded in pixels to suit a certain photo size.

Using CSS how can i get the iphone to display the slideshow-gallery and image with a smaller height compared to displaying it on a desktop or laptop?

Thanks for any help guys!