Iray &Tone mapping

geoff6

Hi all,

When rendering in Iray, which is best; Bright lighting and high fstop value with 100 film iso or low lighting with fast film iso and low fstop value?

Is there an ideal exposure value?

I'm trying to get rid of grainy shadows and textures.

Thanks in advance,

G

JonnyRay

Unlike a real camera, there is no tradeoff between f-stop, film speed, and shutter speed. So it doesn't really matter which you adjust as long as you are comfortable with the results. I also have a habit of setting both Burn Highlights and Crush Blacks to zero and setting the Gamma to 1.0. This gives greater range between the highlights and shadows. However, it will almost certainly create an image that you need to adjust with an image tool afterwards; so if you aren't comfortable with GIMP or Photoshop or the like, you may want to keep the defaults.

As for getting rid of grainy textures / shadows, a couple of general suggestions...

1. Get enough light coverage on the scene. This isn't about how bright the light is, but how many surfaces have direct light from a source verses light that is bounced from another surface. The more that light has to bounce, the more you will struggle with "fireflies". This is especially a problem with interior scenes that don't have very many light sources defined for them. Adding some low level fill lights for surfaces hidden from the main light source can help a lot.
2. I render my images about 50% larger than I want the final image to be. When you shrink the image, the natural sampling which happens in that process averages out a lot of the smaller noise artifacts.

geoff6

Hi Jonny and thanks for the tips, direct light sources in particular, I think I've always been cautious of having too many lights but perhaps I need to let go of that one!

Thanks again,

G

algovincian

geoff6 said:

Hi Jonny and thanks for the tips, direct light sources in particular, I think I've always been cautious of having too many lights but perhaps I need to let go of that one!

Thanks again,

G

It’s the exact opposite in Iray. More light(s) (both intensity and number) will lead to faster resolution.

- Greg

JonnyRay

I will often use one or more of the Iray Ghost Light Kit objects as a "fill" light at a low intensity to add some direct lighting. That may mean I can also reduce other lights as now I only need them for adding highlights & shadows.