I'm trying to get SSAO working in xna 4. The simplest implementation I've found is given in this article: http://www.theorangeduck.com/page/pure-depth-ssao

as it works purely from a depthmap. (the hlsl code I'm using is identical to that in the article)

I'm getting this kind of banding (see attachment).

Based on the directions of the bands, I assume the problem is with my depth map?

Here's the shader I'm using to render it:

float MaxDepth=200;

VertexShaderOutput VertexShaderFunction(VertexShaderInput input)
{
    VertexShaderOutput output;
	
	output.Position=mul(input.Position,WorldViewProjectionMatrix);
        output.Depth=output.Position.z;
    return output;
}


float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0
{
	return float4(input.Depth/MaxDepth,input.Depth/MaxDepth,input.Depth/MaxDepth,1);
}

Can anyone help?

Thanks in advance!

depthCapture = new RenderTarget2D(GraphicsDevice, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height, false, SurfaceFormat.Color, DepthFormat.Depth24Stencil8);

I'm guessing that's my mistake? Should it be Single instead of Color?

Yep, that sorted it thanks. Silly mistake, just reading through the documentation on surface formats made that quite obvious!