Adjusting HDR in environment light

[reform]

Hi everyone. First post here and new houdini user, so be gentle!

I'm trying to understand how one might go about adjusting an HDR within Houdini rather than adjust in another DCC and reload in Houdini.

I tried loading the HDR in to /img/ then adjusting with a color-correct before loading in to the mantra environment light using an "op:" path, but this introduced a painful delay as houdini seems to "cook" all too often even when as far as I would assume, the HDR doesn't need colour corrected until render-time, and even then, only on a per-pixel basis during render.

So, I assume I am approaching this from a totally non-houdini way of thinking. The options as I see them are

1) Adjust the HDR in a different application.

2) Adjust the HDR in the environment light by adjusting the color tint values.

3) Adjust the HDR in the /img/ context and save out with a ROP when satisfied with the result and then pass the direct path to this saved file to the environment light (rather than pathing to the file-in node within \img).

4) Access the file-in node within the environment-light and add a color-correction in there (although when I open the environment light node network, there is no sign of the file-in as one would expect or as you can find in a standard mantra shader node network).

So, I guess my question is, where I have a 'map' in houdini, what is the best way to colour correct the map either by processing outside the object or inside the object node network? (where 'object' could mean primitive/light/shader/etc).

Thanks
 

[fencer]

so,
I took hdr (Dining room of the Ennis-Brown House) from gl.ict.usc.edu (54 mb)

- render time:
direct: 8 sec
from "img": 28 sec
from "img" + color correct: 17 sec

then I changed "File size" parameter to 1/2 resolution
from "img": 14 sec
from "img" + color correct: 13 sec

I think you can try to play with adjustments with 1/2 res or so
than set full for final rendering.

Didn't notice benefits with converting to *.rat

Edited June 21, 2016 by fencer