Workflow for matching colors to image?


#1

Update: After two days without reply, I decided to also ask on the Flamingo nXt forum.

I picked colors from an image of a flat object that I put on a flatbed scanner. However, when I render, then colors come out much brighter. See below: The matte dark blue material comes out light blue. I know that I could adjust brightness in the render dialog. However, that seems a bit random, and furthermore I assume this reduces dynamic range.

When I add a gray ground plane, then automatic exposure is different, and colors are darker. I assume the exposure algorithm stretches the histogram.

In the end I just want accurate colors and neutral lighting, though with a little bit of variation to make metal parts look like metal.

What is a good workflow for matching colors to an image (e.g. a photograph)?


Matte dark blue as picked from the image: rgb(28, 36, 53)

HDR lighting: I am looking for smooth shadows, and a little bit of variation (for metal objects that will also be in the scene).

By default: Exposure is much too bright.

With gray ground plane.


(Brian James) #2

Hi Felix,

I don’t believe there is a way to disable the automatic tone mapping that occurs in nXt, @scottd or @JohnM may know of a way but I think you will have to use the image adjustment settings. To get the same color without a ground plane I used these settings…

The color for the background was also changed to white to make it easier to judge in comparison to the default white ground plane render.

Please email tech@mcneel.com if a question got missed on the forum and you still need help. Apologies on the delay.


#3

Thanks a lot @BrianJ! I also discovered the nXt Image Editor, which allows making these changes at any time post rendering. In particular adjusting burn proved important. From documentation:

Burn

Adjusts the image white point. This is the brightest white color in the image. Burn can add drama, life, and sharpness to a rendering by adding more areas of white to contrast with the dark areas.

Like when post processing a digital photo, I keep an eye on the histogram. The white ground plane is clearly visible as a peak.

Also, I noticed that strong reflections in bare metal can be problematic. Aside from exposure, they also seem to affect white balance. Rotating the model relative to lights (or vice versa), even if using a relatively uniform HDRI environment, can make a huge difference.