Saving the same rendering in dng and TIFF format does not provide the same result. On attached picture, left is the TIFF file and right is the DNG file as seen in Lightroom V6.12. See the artefacts on the dng version. Source are .TIF files from a Fuji camera. In Helicon conversion with DNG converter...

Here was the trick. I went through all menus and miss this box.
Ran the stack from top to bottom of the image and here it is. Just need to crop to my need.

We are 2 photographers just starting with Helicon and we are really enjoying it.
Case close. Thanks.
Sb.

May be already answered somewhere... don't know. Is there a way to increase the canvas size a way it is possible to preserve the whole point of view of the photo stack. To be clearer, see attached file : you see the first picture of the set, the last one, and the resulting - which remove/cut the top...