Scanning the dignitaries at a reception here yesterday, news cameras soon zeroed in on a medium-sized man in a gray, three-piece suit, with steady brown eyes and thinning white hair.

Eduard Shevardnadze, 57, the Soviet Union's new foreign minister, was unquestionably the main attraction here at the commemoration of the 10th anniversary of the Helsinki accords.

With a low-key style and a hesitant manner perhaps natural for a newcomer to international diplomacy, Shevardnadze appeared to help introduce a new note of personal amiability to superpower relations in his debut here this week.

Several hours after concluding a three-hour meeting yesterday, Shevardnadze and U.S. Secretary of State George P. Shultz met again at a harborside reception given by the Finnish government. Followed by a cluster of photographers and journalists, the two men strolled across the lawn to a gazebo, where they lingered for a chat. Their wives carried on a conversation nearby.

It was a scene that would have been hard to imagine before July 2, when Shevardnadze, the party boss from Soviet Georgia, succeeded the veteran foreign minister, Andrei Gromyko, a master negotiator known for his dour, emotionless demeanor. And according to diplomats, it indicated a side of Shevardnadze that was apparent at other meetings during the week.

"We found Mr. Shevardnadze rather sympathique," concluded French Foreign Minister Roland Dumas. "It is manifest," said British Foreign Secretary Geoffrey Howe, "that Mr. Shevardnadze is not Mr. Gromyko."

Shevardnadze's appearance on the scene coincides with a slight warming between the United States and the Soviet Union as both sides prepare for a November summit between Soviet leader Mikhail Gorbachev and President Reagan.

After Shultz delivered a stinging attack on the Soviet human rights record on the conference's first day, the two sides' public comments settled into more practical language, without strident rhetoric.

The slight change in atmospherics was helped along by a better organized, more accessible Soviet public relations effort. During the three-day conference, Soviet Foreign Ministry spokesman Vladimir Lomeiko was available in the corridors of Finlandia Hall to answer questions; Soviet Ambassador to Washington Anatoliy Dobrynin made a rare appearance at a press conference, deftly handling questions from western reporters.

Shevardnadze's wife, Nanuli, a former journalist, also made a good impression here, appearing on Finnish television and touring the city with Helena Shultz.

However, western diplomats were quick to caution that so far, the changes have been of style, not of substance. Neither the new man in the foreign ministry nor the more open approach had been matched by any change in policy, they said.

"It was more a relaxed climate [rather] than a climate of detente," said Dumas, summing up the atmosphere of the conference.

From public forums and private meetings, western foreign ministers and diplomats tried to glean a better sense of their new colleague. The portrait was still a little fuzzy, and there appeared to be a distinction drawn between the Georgian's more relaxed behavior in private and a slight tenseness visible in public appearances.

Diplomats described Shevardnadze as a capable, "competent" man who apparently quickly mastered the material from his briefings, spoke with the help of only a few handwritten notes and displayed a sense of humor and a "lively" manner. One noted that Shevardnadze made grammatical mistakes in Russian. Another described him as a "good politician," while one said he gave the sense of having "an inner compass" that helped guide him despite his inexperience in foreign affairs.

Some observers were struck by a diffidence in his public manner that belied the reputation for toughness, boldness and efficiency he had brought from Georgia.

There, Shevardnadze had made his name as a fighter against corruption, an innovator in economics and an intelligent leader who pioneered the use of television and public opinion surveys. But in a republic that loves the grand gesture and the lavish life style, Shevardnadze also managed to stay modest, both in his personal life and as a political leader.

In comments to the Georgian party Central Committee that hint at the unassuming manner seen here in Helsinki, Shevardnadze reportedly urged criticism of his performance. "Like any other human being I have my faults, and I would like members of the Central Committee to point them out," he said, according to a local newspaper report. "It is simply that I cannot always manage to do everything; sometimes I do not have the time, sometimes I lack the necessary ability or experience."

Now, less than one month into a job that his predecessor had held for almost 27 years, Shevardnadze is starting a new career. Although he has traveled abroad and met individually with diplomats in Moscow, this was his first big forum, and his newness showed.

Reading his speech to the assembled foreign ministers on the conference's first day, Shevardnadze gave a wooden performance, keeping his eyes on the text and occasionally stumbling over words.

In the picture-taking sessions before and after meetings, he sometimes seemed perplexed by the ritual and unsure of how to conduct the obligatory small talk expected on such occasions.

As a result, there were some awkward moments. For instance, as Shultz was introducing Rozanne L. Ridgway, the new assistant secretary of state for European affairs, before their three-hour talks yesterday, Shevardnadze interjected, "In the Soviet Union, as perhaps in your country, we pay particular attention to women. That's the law."