Can rating form tie to webform?

A rating form needs to be designed for a specific layout so that it can display the fields of that layout to the judge.

There is no need to tie it to any particular webform. Just make sure that whatever rating form you use for judging an image was designed for the same layout as the webform the image was uploaded with.

You can have any number of rating forms use the same layout.

In my scenario, I have a layout called FourImages_A. I have two competition categories, Pictorial and Nature. So I created two webforms named Pictorial_A and Nature_A. Both use the same layout FourImages_A. Pictorial images and Nature images are then uploaded with the respectively webform. No problem here.
Then for rating forms, I will have to create two, one for pictorial and one for nature. So what you suggested is the two rating forms (Pictorial-Rating, Nature-Rating) can both use the layout FourImages_A. In such setup, I suspect both pictorial and nature images will be shown to judges in the two rating forms. Would they? Of course the two categories need to be judge separately. I don’t see how this would work for us. Or may be I am missing something.

No. For each rating form you will have to select the webform under which the images were uploaded. So select Pictorial_A for Pictorial-Rating and Nature_A for Nature-Rating,

Ok, that is great. I overlooked this part in the rating form setup page. Thanks for your time.