To begin, let's take a look at the 4:3 SD DVD version of a screencap at the beginning of the series. We can observe a yellowish-greenish tint on the transfer. You and I would probably never think twice about it until we had a chance to view a cleaned up version, along with it being in HD.
And here's the HD version. Notice how the colors are much more consistent from left to right, and up and down. Of course, we don't have that many colors in this particular scene. More importantly, look at the shadows. Instead of having one glob of a black abyss, we can actually see detailed objects within the shadows.
Shown below is a comparative scale view of both screencaps with the 4:3 image overlaid on the HD image, with the 4:3 version being sized to fit the high-def transfer. There's about a 15% addition to the viewing area width of the HD transfer. This is consistent with an originally produced transfer which had the intent of going widescreen.
So, for those who say the original intent of the broadcast was 4:3, they would be right as far as the 1989 television broadcast, but outright wrong as to the type of overall intent of the filming for future presentations (the term Open Matte is now rearing its interesting head).
The broadcast seen back in 1989 would have looked very strange in a true widescreen format. In 1989, there would have been black bars at the top and bottom of the screen, and just imagine how many people would be calling the television stations, complaining about their TV screens being taken over by the Black Bar Aliens. For sure, it was much more prudent to broadcast Lonesome Dove in 4:3, filling up the entire screens of almost every viewer in the US, and they wouldn't be the wiser until 10 years later when widescreen formats would start to take hold, and the DVD format was picking up speed.
Let's grab another section of Lonesome Dove for comparison. But first, the original screencaps from both versions.
In the two screencaps above, we see something different. We observe most of Robert Duvall's hat disappearing in the Blu-ray version. Why is this? Well, this is because I'm lead to believe Lonesome Dove was filmed in an Open Matte process. And because of this type of filming, viewers are used to seeing more information in particular scenes, but in other scenes, minimal differences (like the first comparison above).
Take a look below for another overlay comparison. Not only do we have added horizontal viewing area for the Blu-ray version, we have some information being taken away on the vertical viewing areas for the Blu-ray version as well.
Now, you're probably asking, just why did THEY do this. Well, I'm not entirely sure, but let's take a look at the images again. If you wanted to retain the lower part of Duvall's hat, but still wanted to provide a 16x9 (1.78:1) transfer, you'd end up with something like this:
So now, we have Duvall's hat in the picture. But now we have another problem. Duvall's head is partially chopped. If you compare the Blu-ray screencap and this latest rendering, this is where artistic choice is brought into the mix. The choice to add and/or subtract viewing area in each scene, is very difficult. This was certainly not a Hard Matte process, where the studio decides to just cut the image in a static position. It's evident to me, somebody was meticulously going through the series, making cuts where it was thought was more appropriate. In other words, care was taken into account when making this Blu-ray presentation.
As you can already observe, there's really no "right" or "wrong" presentation. We have the 1989 broadcast version which served a purpose for 20 years. With the advent of HD being more affordable and viable for the consumer, this latest presentation is also available. I can see a possibility where a 4:3 HD version would satisfy the hardcore viewers who were more comfortable. For me personally, I'm enjoying the Blu-ray transfer.