VISUAL EXPLORATION: Photographs by Irene and Milton Weidler, weekdays 8 to 5, through July 13 at the National Arboretum, 24th and R Streets NW.

It's enough to give you a fierce case of them old traveling blues, looking at this picture of the Rocky Mountains. The closest range is intense purple-black, echoed by paler peaks until the jagged formations blend in with the lavender-gray of a misty sky.

Memories are usually much more vivid than the snapshots most people bring back from a cross-country trek - but not the photographs Irene and Milton Weidler took on their travels out west last summer. Their black-and-white and color pictures on exhibit at the National Arboretum are guaranteed to refresh any sagging memory of The Trip or familiarize those not acquainted with the breathtaking natural formations west of the Mississippi.

Shunning the tourist spots on their journey ("If there's a dirt road, we'll take it"), the Weidlers sought out unpopulated spots, stopping frequently to take photographs with their assorted cameras and lenses. When they found a spot with good light and interesting formations, they just kept shooting until dark.

"You have to feel something before you take a picture," Irene Weilder says, "or else it shows up later."

There's plenty of emotion in their photographs. Though the pictures are poorly framed and hung, the dramatic impact still comes through in studies of the snow-capped Tetons with rustic cabins or the clear water of Jackson Lake nestled below. Looking at a partially frozen pond in Yellowstone Park offers a crisp chill.

But it was the desert that most captured the Weidlers' imagination, and their most successful photographs are the hauntingly beautiful dunes in White Sands, New Mexico. It's an orchestra of color: A sinking sun blackens the profile of a sculpted dune in the background. Dwindling light accentuates soft, wavy black lines carved into the sand by wind. The only disruption in this melodic landscape is a lone cluster of thistle, whose purple flowers reach into the sky as the delicate shadows streak across the ground. CAPTION: Picture, A CACTUS IN FIRE VALLERY, NEW MEXICO, BY IRENE WEIDLER AT THE NATIONAL ARBORETUM.