<svg xmlns="http://www.w3.org/2000/svg">

<defs>
<filter id="light" primitiveUnits="userSpaceOnUse">
<feSpecularLighting lighting-color="blue" surfaceScale="5" specularConstant="10" specularExponent="6">
    <feDistantLight azimuth="0" elevation="30"/>
</feSpecularLighting>
</filter>
</defs>

<rect width="40" height="20" filter="url(#light)" fill="black"/>

</svg>