So, I upgraded to 5.2 and was initially disappointed in the results. This time my comments to DXO were answered immediately by one of their customer service representatives ( Gaël ).

Gaël suggested that my problem with reduced visibility of shadow detail with 5.2 compared to 4.5 was due to the fact that there were changes in the default settings of 5.2 compared to 4.5:

"Thanks for replying. Version 5 lighting default changed from medium to slight.
That might explain the differences in shadow areas, and the sharpness sensation, the
"local contrast" parameter of the lighting palette is involved in the sensation of sharpness.


If you want to have similar images I would recomend changing
the lighting default by "Medium".

Would you try this setting and let me know if that change
the look of your images?"


I went back and re-processed several of the images that I had redone earlier today along with several of the ISO 1600 images that I had been so disappointed with a few weeks ago with 5.1. After doing this, the sharpness was up to the level that I had been seeing with DXO 4.5 and the shadow detail was restored to at least as good as it had been with 4.5.

A big difference was visible when I viewed the ISO 1600 images in extreme close-ups ( done by going to iPhoto, moving the slider all the way to the right and then holding down the "Control" key and dialing the spinner dial on my Logitech mouse forward to make a gigantic image of a tiny part of the photo. The resulting detail visible was much smoother and less jaggy mottled looking than the same photo processed in 4.5.

Changing the lighting default from "slight" to "medium" made all the difference and made DXO a "must have" as far as I'm concerned.