IN A dimly lighted room of the Boston Museum of Fine Arts a lady pointed her glove at two almost identical prints of a round faced artist sitting near a window. "Can you see the difference?" she asked the boy standing next to her. And showed him where a shadow of tightly woven lines crept over the side of the face in one print, softening the mouth and eyes. This conversation startled the carpeted gallery out of its silence. Businessmen, students and more ladies offered advice in distinguishing the difference between other apparently similar prints, exhibited around the room.

As their eyes adjusted to the darkly inked surfaces, changes in detail emerged. And eventually a row of five landscapes neatly placed on the wall, like copies of a photograph, dissembled before the viewers into individual images, each with its own mood. It became clear that without changing the basic design, an artist can adjust the components of ink paper or line and produce an image of different quality.

Exploiting all techniques of 17th century printing processes, Rembrandt continually reworked his etchings to find a more expressive image, By emphasizing the changes he made on a single plate, the exhibition currently at the Boston Museum of Fine Arts shows the evolution of impressions from the same print. Though each landscape or biblical scene is complete in itself, it forms a step in the growth of the artist's progressive conception of a print. This small but awesome exhibition, Rembrandt: Experimental Etcher, honors the artist by following his creative process.

The brown, grey and yellow panels on which the prints are exhibited harmonize with the paper colors of the prints themselves and quietly offset the black etched lines. The subtle installation does not distract the viewer in his investigation of the intricate linear designs.

A catalogue printed in the same parchment tones of the prints describes the techniques Rembrandt used to create his shadowy imagery. He juggled lines - etched, and engraved - according to what he drew, sometimes combining all three in one print. He worked the delicately teethed lines into the most careful description-to weave the wrinkles in a face or show the heaviness of a drapery. He employed rougher drypoint or engraved lines for bolder cuts.

Restlessly attempting to improve his work, Rembrandt would add or remove lines from the copper plate with which he printed. According to the catalogue, alteration of this plate constitutes a change of "state" in the print. But within each state the artist experimented with ink and paper tone. Rembrandt often printed an image on particularly dark or absorbent paper to soften the black lines. Sometimes by wiping the ink off the plate before printing, he let light from the surface of the paper glow through the network of lines. Intricate juxtaposition of black and white makes the billowing robe of a priest glitter as though it were done in black and gold oil paint.

In the various versions of one portrait. Rembrandt explored the complexity of his character. He drew his friends: a lawyer, a merchant and Clement de Jonghe, a print seller from Amsterdam. All editions of the portrait of de Jonghe have the same skeletal composition. His strong body is buttoned into a jacket and surrounded by a cape. He sits leaning on the arm of a straight-backed chair, gloved hands resting in front of him. He carries a large-brimmed hat as though it were part of his head.

THE FIRST state of the print is a general statement. But in the second state Rembrandt refined the face, darkening the curve of the lips, and enunciating the cheek. One eye, large and black, opens in a tentative expression. The other one tightens in its scrutiny of the viewer. Rembrandt again blurred the features in a third state. Now the eyes are of equal size. And an arch scratched in at the top of the page brings de Jonghe forward. Finally Rembrandt cut deep shadows into the cape grabbing the focus away from the face. And the print seller becomes an able cosmopolitan.

The miniscule changes in de Jonghe's facial expression suggest conflicting thoughts. Does the sitter look different because his mood changed each time he posed for Rembrandt, or did Rembrandt merely illustrate a different aspect of his nature? Or is it the artist's own opinion of de Jonghe that develops through the changing states? The prints spin out the shifting relationship between artists and sitter. Beyond this the progression suggests that changes within the viewer himself will make a print appear different each time he approaches it.

The biblical scenes, though born in the artist's imagination, are as alive as the portraits. Filled with bunched bodies and old faces these master pieces appeal even to the skeptical modern eye. Concentrating on the crowd, some doubting, some frightened, some barely paying attention, Rembrandt depicted how ordinary people react to Christ in the course of day-to-day existence. The warmth emanating from Christ incorporates itself in details among people, in a calm face or one hand leading another.

He described people the way we see them-all ages and sorts-and our eyes trust his images. Often unable to articulate his feeling in a line, he immersed a scene in a shadow. Some of the prints, like "The Adoration of the Shepherds: A Night Piece," are almost completely black. A box-like lamp, held by a shepherd sends light shimmering through the mesh of lines on the surface of the paper. Only the faces glow from the mysterious night in the stable. The artist expressed the wonder of the people present by unifying them in darkness.

The changes Rembrandt made in his prints are further evidence of the energy with which he sought to discover the truth about everything he drew. Not limiting himself to one idea, he expanded his conceptions, letting them change direction when he found something new in either his subject or himself.