Before we start improving the details within the luminance image, we need to stretch it to non-linear. The stretch on the luminance is different than the stretch for the color image. For luminance, we will do two different types of stretches. want the background to be darker than the color image.

Masked Stretch

I used masked stretch for my color image and I will use it for my luminance image as the first part of the luminance stretch. Once modification I make is that the target background value for the luminance is lower than the one selected for the color image. I want my luminance background to be darker.

Exponential Transformation

The second part of the luminance stretch is to use the Exponential Transformation process. The exponential transformation with the Power of Inverted Pixels function allows us to brighten the image without brightening the background or overpowering the brightest regions. You can think of it like creating a slight S-curve in curves transformation. It adds contrast without impacting the background brightness.

What’s Next

Save this file as the Luminance image.

To enhance luminance, we will use a combination of

The next step is focus our attention on the bright areas of the image with HDR Transformation.