How to increase the resolution of a rendered image? When I increased the resolution on the Render tab and enlarged the image in the camera, the edges of the objects were blurred. How can this be fixed?
Given that the question is about resolution.
See that slider that shows 35% in the resolution settings?
You are rendering an image that is rougly a third of the resolution. Instead of 1200 pixels you are rendering only 420.
Set the value to 100%

As for why the picture is blurry, there is no  information on the question that can yield a conclusive answer. The focus or depth of field of the camera might be set incorrectly, or there might be some nodes in the compositor we don't know about.