HDRI Community

1. Yes, and there's a lot to be found on 'hdri bracketing sheet':
http://www.digitalcameraworld.com/2013/11/13/exposure-bracketing-how-to-do-it-ma...
If you're going to do a lot of HDRI photography, I do recommend a Promote or alike for speed and ease of use.

2. The 'norm' for 3D is mostly longlat, or a 360/180dgr. pano. But there's more ways to skin a cat...

3. It depends. I normally shoot with +/-1 incr. when inside, and +/-2 when outside. When there's low light I like to have a bit more steps to have some more control on image noise.

4. I think you mean 3 step -/+2?
Not with your camera. Only some camera's do that with stock ROM's, or are programmable to make your own.

5. If you're just compositing your 1 frame 3D render on the backplate, you -could- do it all in so called 'floating point' or 'non-linear'. That is, when you shot the backplate in brackets as well.
But normally, when compositing in moving footage, the backplates (video) is a non-hdri (non 32 bit) format.
It's a whole other discussion about bitdepth, color spaces, white balance etc.

rob

Correct.

But most compositors, even the free Natron, work internally with 32 bit.
And with compositors I don't mean Photoshop.

So you could shoot a single backplate with brackets, and make a 32 bit file out of it. Render your 3d in .exr or alike and composite.
When you're finished , render out the composite to a ldr format like jpg, png, tif or alike.
That way you'll stay in 'float' until the end of the 'line'.

rob

again, this is a whole other discussion