Mastering 4:3 Versus 16:9
Here is a comparison between 4:3 and 16:9 aspect ratios when content is mastered.
4:3 on the left, 16:9 on the right.
Here you can see in the Seinfeld episode The Heart Attack the differences in both versions.
On the left is the 4:3 from a PAL VHS tape which originally recorded the broadcast from the channel TV1 on Foxtel some time in August 1999.
The one on the right is a 1080p stream.
The 4:3 broadcast has the sides cut as you can see from George and Jerry's shoulders and even part of Jerry's head but more detail can be seen at the bottom such as the blanket and George's right hand.
In the 16:9 stream much more detail can be seen on the sides but the bottom is cut out.
Seinfeld was recorded using Panavision cameras.