Canvas not working properly

Whenever I have a large layout and a canvas, the canvas only works in the upper left hand corner. I've discovered that this is directly related to the resolution of the application window. For example: in my top down shooter game, I want to paste blood to the canvas. I have the view centered on the character. If I shoot an enemy outside of the upper left hand corner, there will be no blood pasted onto the canvas. The larger the window resolution, the larger the canvas working size. I'm sorry if this isn't the best explanation, but does anyone know how to fix this?

If there is no way to fix this, is there some sort of workaround? Like a render to texture plugin?

Canvas uses the gpu to do the capture, so if part of the image isn't on screen, it cant be used.

There is no fix, other than to use the draw actions.

Also as you may have noticed canvas uses a lot of memory, so huge ones aren't suggested.