1984 Donruss blurred circles

I am today years old to realize the 1984 Donruss set had at least 46 cards that had intentional blur in the background. Most of them are blurred with whitish circles over what I assume are fan faces. Was this because they didn't want to be libel for some reason? There may be a full-on explanation somewhere already done but sometimes I like to do this on my own before learning about it. Either way, some of them are pretty artistic-looking and I am considering buying them for that sole purpose.

I was initially searching on TCDB for old Comiskey Scoreboard backgrounds in this set, none of which I saw, but I realized many cards had the intentional blur so I started jotting them down and came up with at least 46, but some with a lesser extent of circles. 1981 Fleer is THE set for Comiskey and Wrigley backgrounds but was hoping to find more in this set. But these are my favorite blurred-circle cards in the 1984 Donruss set:

#121 Dave Concepcion	#138 Glenn Brummer
#184 Gary Redus	#311 Ryne Sandberg
#433 Jody Davis	#470 Ken Landreaux
#529 Ron Reed	#563 Brian Giles

These are all the cards that have more blurred circles, to a lesser or greater extent, on them: 35 59 71 94 121 137 138 155 157 176 184 189 207 223 253 293 296 301 305 311 315 333 367 377 381 383 384 395 399 400 422 429 433 437 459 470 488 494 499 506 512 514 529 541 552 559 563 606 610 633 649

UPDATE: I was just informed by @vossbrink on Twitter that the blurred circles is catadioptric bokeh caused by using mirror lenses. Nick also stated this happened a lot in vintage sets. I don't look at vintage much so this is the first I'm noticing it.