Need help scaling images to fit slide show

When I first began to use wordpress, I had no problem with the sizing of images. The images I uploaded to my portfolio always fit on the page. After updating the wordpress theme a few times, all vertical photos in portfolio are humungous, you have to scroll down in order to see the full image. I have tried deleting the photo and re-uploading it, making sure that it is a small enough size. Still there is no change. Please help!