contour plot does not match matrix contours

Hello,

Assume I have the following matrix:

A=[1 2 3 4;2 3 4 5;3 4 5 6;4 5 6 7]

If I create the following plots:

figure; imagesc(A)

figure; contour(A)

The displayed contour lines do not line up with the constant values in the matrix. They are rotated 90 degrees from the imagesc plot. I have attached 2 pictures to show what I mean.

However, if the matrix is:

B = [1 2 3; 1 2 3; 1 2 3]

The two types of plots will match up.

Why does the contour plot apear to rotate the constant value lines when the gradient is angled?

Thanks