In a brightly lit, modern federal courtroom, some of Washington's keenest legal minds had turned their attention to a huge, aerial photograph of city buildings that had just been likened to a blurred portrait of a "junkyard."

The sharp debate prompted by the controversial photo represented one move in a complex legal chess match that has been under way for three weeks since the start of the bribery and conspiracy trial of D.C. mayoral aide Joseph P. Yeldell and millionaire real estate developer Deominic F. Antonelli Jr.

The contest has pitted a defense team headed by a nationally known lawyer, Edward Bennett Williams, and a highly regarded Washington attorney, John A. Shorter Jr., against three aggressive federal prosecutors - Richard L. Beizer, Henry F. Schuelke III and Michael Lehr. The legal bout is being refereed by Judge Gerhard A. Gesell, who is regarded as an astute and even-handed jurist.

The match of legal wits has helped pack the courtroom audience day after day with government and private attorneys. They come to watch and hear recognized experts in the art of cross-examination in a much-publicized U.S. District Court trial. What impact the legal jousting has had on the jury has remained - as in most trials - an unanswerable enigma. The jurors have been sequestered and instructed not to discuss the trial even with one another.

The Oct. 5 battle over the aerial photo was one of a series of legal skirmishes that have marked the trial. Other disputes have centered on real estate charts, diagrams about financial transactions, tape recordings of a March 1977 interview of Yeldell by city auditors, key questions the prosecutors wanted to pose to several witnesses, and conflicting views about the instructions that will be given to the jurors before they begin weighing their verdict.

It was Williams who led the fight against the big black-and-white aerial photo, which depicted a cluster of Northeast Washington buildings, most of them owned by one of Antonelli's partnerships. The prosecution wanted to show the photo the jury. Williams countered by denouncing the photo as "highly inflammatory" and "grossly misleading."

"This looks like a junkyard, and a bad junkyard at that," he told Gesell.

The battle over the photo ended in a victory for Williams - a relatively minor triumph in a trial in which he has suffered some defeats. Gesell agreed that the photo did, indeed, resemble a junkyard and ruled, on narrower grounds, that he would not permit the prosecution to show it to the jury at that point in the trial.

The defense team's defeats have included an unsuccessful effort to block the prosecution from asking witnesses a key question - whether Yeldell ever disclosed to them his personal financial relationship with Antonelli. The prosecution had sought to ask this question in an attempt to prove that Yeldell had concealed his ties with the millionaire developer and parking company owner from city government officials - a central point in the charges on which the two men have been indicted.

Gesell eventually allowed proseuctors to ask the question of several witnesses, all of whom acknowledged that they had been unaware of the two defendants' financial ties.

Yeldell and Antonelli are charged in a grand jury indictment with conspiring corruptly to arrange a lucrative city government lease for a partnership controlled by Antonelli in exchange for Antonelli's help in providing loans to Yeldel.

Williams and Shorter, Heldell's defense lawyers, have established reputations as skilled cross-examiners. But the most dramatic cross-examination in the trial was Assistant U.S. Attorney Beizer's prolonged and pointed interrogation last week and Yeldell. At that time the former city human resources director was shown to have repeatedly made false, misleading, incomplete or contradictory statements to city government investigators about his dealings with Antonelli, in financial statements submitted to government and private agencies and in his own court testimony.

At one point, Yeldell said under questioning by Beiezr that he had had a loan document notarized by a secretary at his city government office. When Beizer produced attendence records to show that the secretary was on leave on the date, Yeldell conceded that the document was not notarized at his office but had been sent to the secretary's home.

At another point, Beizer asked Yeldell how he could have known that Antonelli's name did not appear on a promissory note if he had not read the note at the time. Yeldell had testified that he had not examined the note at the time he received the secret $33,000 loan from Antonelli. Confronted with Beizer's question, Yeldell acknowledged that his earlier court testimony was inaccurate. "I am sorry - I shouldn't have answered it that way because I do not know, I did not look at the note," Yeldell said.

"But you were under oath," Beizer responded.

"I did not look at the note," Yeldell replied.

"Did you know that Mr. Antonelli's name was not on the note?" Beizer asked a few moments later, hammering at his earlier question.

"In terms of physical examination (of the note), no," Yeldell replied.

Occasionally, the cross-examination probing has appeared to backfire. At one point while undergoing cross-examination by Williams, Sam D. Starobin, the city's general services director, shot back, "You're playing with my works."

Edgar B. Madsen, a real estate appraiser who was being cross-examined by Williams, responded to a series of questions with a stern lecture. "If you jump around and make one assumption over here and one assumption over there," he told Williams, "you get confusion."

Much of the lawyers' strategy - including such key questions as why the defense chose to put Yeldell and Antonelli on the witness stand - has nevertheless, remained a matter of speculation. The lawyers rarely have commented publicly on their moves. Asked about one courtroom maneuver early in the trial, Williams told a reporter, "If I told you, you'd write what you want to write anyway. So why should I tell?"