HDRI Community

Hi All,

So I been playing around with picturenaut / shooting hdrs and I'm wondering if someone can explain the following: 

I shot a hdr of an office room that has very strong small lights in the ceiling resulting in high values, I also turned on a softbox, and it's daytime with big windows (no sun).

they are all shot right after each other so lighting didn't change, canon 6d 8mm fisheye, 3 angles argb raw to > hdr in ptgui

I thought I'll test different techniques of shooting it to see the EV results / clamping:

7 shots @ 1 evs apart
results in 13EVs in picturenaut
Light clamping is pretty bad and value is around 3 (of the small lights in the ceiling)
Lighting results are very inaccurate indeed in 3D(testRender)

7 shots @ 2 evs apart
results in 24EVs in picturenaut
Light is still clamping, however value is around 30
Lighting results are ok in 3D, fairly nice shadows etc, not perfect..(testRender)

7 shots @ 3 evs apart
results in 20EVs in picturenaut!? Guess it's because the steps are larger? Surely the Evs should still be higher no?
Light clamping is good, captured most of the range
Value around 300-500
Lighting results in very nice shadows etc in 3D (TestRender)

Now just as a test, I downsized the same image (20 EVs) to 10% of the original (700px by 300) from (7000 by 3000), brought it back to picturenaut: 34Evs, what..?
Test render in 3D, results are indeed same as 20ev.

Can someone explain how the EVs are calculated in picturenaut?

Also based on this, EVs are not a very accurate measurement of "quality" of an hdr as 20EVS, 7 shots, 3 steps results in better lighting vs 24EVs 7 shots, 2 steps.

To my understanding the more EVs a high contrast lighting hdr has, the higher quality it is? I guess not necessarily based on this?

Can attach images if requred.
Thanks,