Sizes of Canvases We Can Get

In order for our thriller shoot to work properly, we need three canvases to maintain continuity throughout the video.
There are several sizes that may be available to us from the art department; A1, A2, and A3.
Since we need three canvases, and as they are quite expensive, we have to look at what would probably be most useful to us.
In order for the canvas to fill up the easel and make it prominent, we would need an A1 canvas - the sizes of this type of canvas would roughly be 594 x 841; however the art department doesn't currently have enough A1 canvases available, so in order for us to get them we would have to go into an art store and purchase them.
An A2 canvas would be half the size of an A1 canvas, so 420 x 594 - this means that the canvas would not fill up the entire easel and would most likely make the entire thing look less impressive.
Lastly, an A3 canvas is yet again half the size of an A2 canvas, meaning that it would be 297 x 420 and would probably be left unnoticed when shooting the thriller.