You are using a flexible width theme which means the size of the post area changes with the width of a browser window. Resize the width of your browser window and you will see what I mean. This means that for people who have their browser window set narrow, or have a lower resolution monitor setting, they will probably not see your entire photograph. It is the nature of flexible width themes.
If you look at this blog post, http://wpbtips.wordpress.com/2009/07/23/maximum-image-width/ , and look in the far right column, you will see the actual maximum image with for the various themes here. If you put images into a post that exceed the maximum image width listed there in the right column, it can in many case cause your theme to break and go seriously wonky.
The themes with the widest post areas as you will see are the two journalist themes.
Images do not automatically resize when you go to the post permalink page. If they did you would be relying on the browser to resize the image, and the image would come out looking very bad. Browsers do not resample, they only resize and for the most part do a pretty poor job of it.
My suggestion is to find a fixed width theme you like and then insert images into your posts to where they fit properly and then link that image to the full-sized image. Then people can click on the image in the post to see the full-sized image.