Blog "Posts Page" not retreiving value for field

I’m using ACF to override header images, on a per page basis. The logic works correctly on all regular WordPress pages. When I upload an image to the ‘Blog’ page which I’ve assigned to become the “posts page” under Settings > Reading, the ACF get_field(‘image’) that is in use on many other pages doesn’t retrieve a value.

I have an if statement, that says, if get_field(‘image’) has an image, then display the image, otherwise show me the default image. It keeps kicking back the default image.

Is there something up with it because it’s a “posts page”? When I set the Blog page to not be a “posts page”, it retrieves the value and displays the override image.

http://wordpress.org/plugins/advanced-custom-fields/