Context

So I've seen light painting shots and I'd like to try it out sometime. I'm more interested in painting say parts of the landscape so they stand out during a long exposure.

Question

Is there any candela equation for finding out given the amount of candela how much reach it will have? If no, are there recommendations or related for that? Do manufacturers actually post valid results or are they also fudged? Are there specific features that should be considered when shopping?

Partial Answer

I assume for features I'd need to look at battery life and what throws it has but doesn't tell me how far the light beam can necessarily travel. Of course this changes in fog or other environments but in my case I'm aiming for a clear, or clear enough night.

Related

How do I get started with 'painting with light' photography?