How do the various built-in renderers (Karma, GL, Storm) handle camera scale? Does it have to be considered again?

I'd imagine any camera scaling would affect all renderers in different, subtle and sometimes not-so-subtle ways. I'm not aware of any comprehensive standard for it, myself. I would just say, as always, JUST DON'T DO IT!

Agreed!

However in recent versions Mantra would by default strip away camera scale, meaning it was no longer a big concern with Houdini renders. I'm not sure about Arnold or others, however.

It was nice of Mantra to do that, yes Renders have all sorts of sampling biases, variances and thresholds that are based on different spaces that you may or may not expect a scaled camera to affect, that I would do whatever it takes to apply a camera ‘harness’ and keep it at identity as much as possible.

Yes. In any case, what's nice about Solaris is how many ways there are to “fix” problems like that in a pipeline-able way.

If you need to scale the camera for viewport visibility, you can scale that geometry without scaling the whole thing. Just dive into that node, and you can put a transform node there.

I was wrong, it doesn't work in LOPs, just in geo/SOPs… but now:

Light and Camera LOPs now have a “Guide Scale” parameter which controls the size of the guide geometry for these primitives in the viewport. The default value for these parameters sets the value to the inverse of the meters per unit value of the stage, producing a consistent real-world size for these primitives. The camera LOP also has a parameter that can hide the camera from the viewport camera menu (in cases where the camera is for utility purposes, not meant for looking through).

https://www.sidefx.com/changelog/?journal=&categories=&body=&version=18.5&build_0=417&build_1=417&show_versions=on&show_compatibility=on&items_per_page= [www.sidefx.com]

Cool, that helps for visualization!