render image inside ejs template in nodejs express

I'm trying to render an image inside an ejs template. I;m doing this:

var pic = "./public/images/"+collection_id+"/"+photo_id+".png";
var comments = "bla bla bla";
res.render('index', { title: 'Viewer' , pic: pic , comments: comments } );

and inside my .ejs

<img src='<%= pic %>' />

I found out however that the true request is

GET /collection/1/photo/public/images/1/1.png 404 1ms

where /collection/1/photo/1 is the URL that I'm trying to route

what can I do in order to render the image inside the template?