Why doesn't noise reduction have any effect in Rawtherapee?

Question

I am processing some raw images from my Canon camera.

I am using Rawtherapee on a Mac desktop.

When I try to apply noise reduction, the changes are not taking place, or at the very least are not being perceived by me.

I have a very noisy image from a high ISO setting as my test image. So it is definitely a good candidate for noise reduction.

I have hit the enabled button for both "impulse noise reduction" and "noise reduction". I have put the sliders full in all directions.

I do not notice one bit of difference in the noise reduction.

Answer 1

You can only preview noise reduction in RT when you zoom image to 100%, even in latest version.

Many other tools have same limitations for previewing, they are marked with small "1:1" label near their names.

Answer 2

Many previews in image editing applications are just that - previews. To get an exact view of what many effects and settings applied to an image will look like you should export the image with the changes applied. Since this can be rather tedious and cumbersome, previews allow us to see an approximation. Many noise reduction tools, including RawTherapee, only provide noise reduction changes in previews that are viewed at 100% (zoomed in so that one camera pixel equals one screen pixel).