I have been using Negative Lab Pro for a long time now, and overall it is satisfactory, except for one problem that always happens to me: the white balance varies between light and dark tones. This is particularly noticeable in photos of gray objects, such as stone statues or monuments. Dark areas tend to be slightly blue or green, and lighter areas come out in orange tones. It is obviously subtle, but it is visible. If I were to shoot a perfectly neutral gray gradient, it would be rendered with blue areas and other orange areas, depending on the density of the area.
I am using a flash as the light source (Nikon SB 600), and a Nikon D750 DSLR. I tried with another flash, same result. I put a UV filter in front of the flash, no change. I used two different macro lens, no change.
Films may vary (new Kodak Portra 160, expired Portra 400, archival color negatives of various brands, etc.), but the problem is still there.
Do you have the same problem?
Here is an example (it’s a crop) :