I believe the problem is the trailing , info call. It is looking in the info object for img_style. You don't need it.
I love using partials but recently have seen the beauty in helper methods too, especially in simple renderings like this one.
def info_image(info, class_name="original")
image_tag(info.image.url, :class => class_name)
end
then just
<%= info_image(first) %>
or
<%= info_image(first, "anotherclass") %>
in the view. Much cleaner.
If ever it becomes more complex. You'll only have to change code in one place.