Code
Texture2D MyTexture;


float4 FP(float2 fragCoord: VPOS) : COLOR
{
	/// ... ///
	
	float3 col = MyTexture.SampleLevel(postTex, UV+n, focus).rgb;
	
	/// ... ///
}


i think "SampleLevel" is part of shader 4.0. (Minimum dx10)