Blu-ray transfer of old movies

[pinbuoy]

Hello,

I"ve seen some threads cover part of this question, so I apologize for any duplication. This is kind of a rambling 2-3 part question, answer the part that's applicable and thanks.

How far back were movies filmed in HD, or what is the typical resolution that movies were filmed at, say 5 or 10 years ago?

Is the transfer to Blu Ray just a "factory upscaling"?
Is there a cutoff date where it would be better to save your money and watch a SD upscaled then to spend $20-$35 on the Blu Ray disc if it displayed at the same or lower quality?

OR ;-) are there just too many variables between differing quality of transfers, tvs and upscaling players to make such a blanket statement?

Thanks

Mike