Underexposed Phys Cam: decrease f-stop or increase HDRI output?

[landrvr1]

Wondering what's going to be the best way to go in order to reduce rendertimes? Ive got the HDRI mapped to a domelight and control the output in a V-Ray HDRI material. Just starting some tests but was curious as to thoughts? The ISO is at 200 and shutter at 60: I'd like to keep those settings because it gives me very nice blurring effects on moving objects.

Tnx

[Neilg]

No difference. If they both get the scene to the same level of brightness then the render times will be the same.

[landrvr1]

Okay, tnx.

[trixian]

There is one difference, aperture affects dof etc. iso doesn't. Who knows if he needs dof after the fact? Besides, the logical choice is adjusting iso, especially when playing with motion blur, dof and such, for less confusion down the line.

[peterguthrie]

I use this http://www.giangrandi.ch/optics/lenses/expcalc.html when I need to keep the overall exposure the same but want to change the shutter speed (for mblur effects) or aperture (for DOF)

As Christian says, its often best to adjust the ISO as unlike in real cameras it doesn't affect noise.