SOMETIMES just after things improve they turn worse than ever. So it has gone with popcorn. As it has revived in popularity, movie theaters have gone to greater lengths to sell it fresh-popped, with the option of buttered or unbuttered. And for home consumption, manufacturers have packaged it in handy microwavable bags.

But now the downswing: The last few times I've bought unbuttered popcorn at the movies (most recently at the Biograph) it has been coated with some dreadful residue -- gluey, grainy and greasy -- which clings to your palate longer than the movie sticks in your mind.

And at home, even the unbuttered versions of microwavable popcorn have been similarly greasy and mouth-coating, the worst of them the status-seeking Orville Redenbacher, which filled the house with such a strong greasy smell that my daughter was prompted to take out the garbage.

Here is a clear case where less is more. A tiny bit of plain oil and salt is all popcorn needs to be delicious. There is no reason that unbuttered popcorn should be greasy, and certainly not grainy and mouthcoating.

SOFT SELLS FOR SOFT-SHELLS -- While they're still around, soft-shell crabs are irresistible, as dinner and as conversation. So, after a survey we ran a few weeks ago of interesting presentations of soft-shells, it is time for a survey of the most interesting prices for them. Keep in mind that the wholesale cost of soft-shells is about $1.50 to $3 apiece, depending on the day and the size. Also, remember that sometimes the "fresh" soft-shells on the menu are defrosted soft-shells on the plate.

Within the past two weeks a telephone check of restaurants' dinnertime prices found Perry's, at the corner of Columbia Road and Biltmore Street NW, cheapest with two soft-shells (and two side dishes) for $7. Ocean Garden in Silver Spring was close with three jumbo soft-shells at $9.50. After those came Tivoli in Rosslyn, three for $12.50; R.T.'s in Alexandria, three for $14; Spectrum downtown, three for $14; Misty Harbor in Rockville, two or three for about $12.50; China Coral in Chevy Chase, two to 2 1/2 (they are cut up) for $12.95; and Mrs. Simpson's on Connecticut Avenue, two for $13.95.

A DAY IN THE PARK -- Galileo is, like no other restaurant I know, recognizing modern necessities; the restaurant is offering free valet parking for lunch, not just for dinner.

SERVER OF THE WEEK -- The new Vie de France Fast & Fresh cafeteria and carryout at 1615 M St. NW can be confusing for a newcomer, but not if a waitress named Angelina is on duty. She not only approaches customers who look lost and shows them what's where, she also helps them to bag their carryout foods, even taking the trouble to double-bag ones that might leak. Furthermore, Angelina says she makes the best salads in the place; if she showers half the attention on salads that she showers on customers, it must be true.