SVG effect becomes "dim" on higher resolutions

[LaurenzV]

Given the following SVG:

<svg id="svg1" viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
    <title>lighting-color=hsla (SVG 2)</title>
    <desc>Looks like alpha should be ignored.</desc>

    <radialGradient id="rg1" r="0.5">
        <stop offset="0.5" stop-color="white"/>
        <stop offset="1" stop-color="black" stop-opacity="0"/>
    </radialGradient>
    <filter id="filter1" color-interpolation-filters="sRGB">
        <feSpecularLighting in="SourceAlpha" lighting-color="hsla(120, 100%, 25%, 0.5)"
                            specularConstant="8" specularExponent="10">
            <fePointLight x="100" y="100" z="10"/>
        </feSpecularLighting>
    </filter>
    <rect id="rect1" x="20" y="20" width="160" height="160"
          fill="url(#rg1)" filter="url(#filter1)"/>

    <!-- image frame -->
    <rect id="frame" x="1" y="1" width="198" height="198" fill="none" stroke="black"/>
</svg>

Rendering with cargo run -- test.svg test.png --background white yields the following result:

As you can see, there is a pretty clear white circle around the center.

Now I render with cargo run -- test.svg test.png --background white --zoom 4 and I get:

If you look closely, there is still a very dim white circle around it, but it's much less visible than before. Is this intended?

[LaurenzV]

For what it's worth, it seems like the same happens in Firefox, but not in Chrome.

[RazrFalcon]

Lighting effects are effectively UB (undefined behavior) and every SVG library does whatever it wants.
Unless the SVG spec clarifies the expected behavior - we're out of luck.

If someone is willing to figure out what Chrome does differently - feel free to send a PR.

PS: A reminder, that SVG has non-reproducible rendering by design.