volumetric spot without infinitely small start point

[Steve Bentley]

Got it.
Wrapped a transparent grad texture around the light itself using a cylindrical mapping.

[Brian Jones]

easier solution, in the Details tab of the light object enable Near Clip and set the To and From values. ‘From’ defaults to 0 and it fades in over the distance to the To value – in the viewport the light object has a couple of blue indicators that move as you adjust the From and To…

[Steve Bentley]

Thanks Brian, I did try that – it was my first “this will work” without even thinking. But it didn’t do anything.
The texture map on the light itself work brilliantly – even if it was somewhat clumsy to get the look I wanted.

Here’s a follow up – I’m finding the diminishment of the visible light as the light peters out to be quite harsh. I’ve tried combining the standard falloff (which doesn’t seem to have an effect on the visible volumetrics – both linear and inversSQ), I’ve also tried using the texture map I wrapped around it to add some more tape to the falloff – this did work but the ending of the light is still fairly abrupt. I realize it’s a cheat and that the volumetric is just a smear of whatever shape it’s passing through (and I have my samples down to 5 so i don’t get popping when it animates).
Is there a trick or is it just the nature of the beast? A cone of light that tapers at the wide end to nothing reminds me of a cube of aerogel where the edges are almost not there yet you know there is a hard wall there ending the volume, especially if you aren’t looking side on at the cone and you can see some of the ellipse of the cone cross section.

To be fair it might be that I’ve got the apex of the cone cranked so that I get a good bloom of the color of the light soaking out to almost light saber white.