Are you talking the soft focus filter they use in the movie Mame? That's exactly why they did it. Lucille thought she did't look good for the big screen and they used the soft focus technique to hide her now growing older faults. I have also noticed this in the Doris Day Show, what movies of Doris' did they do it in?
Lucy is also out of focus in "Critic's Choice". But that was ten years before "Mame". The teased lensing is less obvious. Cigarettes, California sun and alcohol aged Lucy a great deal. She had a good team of makeup artists and special effects cameramen to keep her glamour intact. Doris Day used the soft focus stuff to hide her freckles!!
"Pillow Talk", "Do Not Disturb", "Move Over Darling" TO NAME JUST A FEW. Because Ms. Day had crowsfeet in addition to an abundance of freckles. During the 1940s and 50s, Doris Day had a pastey, almost waxy foundation used to conceal her freckles.
Despite crow's feet and freckles, I think Doris Day has a timeless "girl next door," innocent beauty. She's remained lovely her entire life. And, I love her movies. No matter what, they make me feel better about life.