Eastman Kodak Co., the nation's leading supplier of photographic equipment, said yesterday that its second-quarter net profit was 47 percent higher than in the same period a year ago.

The company said its net income rose to $191.8 million ($1.19 a share) from $135.1 million (84 cents). Kodak's sales were $1.56 billion, up from $1.35 billion last year.

Water Fallon, chairman, and Colboy Chandler, president, attributed the sharp rise primarily to increased unit volume and improved productivity.

Led by strong gains in photographic products, all of the company's operating divisions contributed to the improvement in sales compared with a year ago, Fallon and Chandler's statement said.

Kodak's net profit for the first half gained 45 percent to $338.8 million ($2.06) from $229.3 million ($1.42) last year. Sales climbed to $2.94 billion from $2.55 billion a year ago, Kodak said.

Polaroid Corp., Kodak's rival in the instant-camera market, Tuesday reported increases of 28 percent in both sales and earnings during the second quarter.

American Airlines Inc., the nation's second largest airline, reported record second-quarter earnings and sales yesterday and predicted record profits for the current year.

And Braniff International Corp., the eight largest airline, said its profits and revenues also set records for both the second quarter and first half.

Their reports followed Tuesday's announcements of record profits for the quarter by UAL Inc., Trans World Airlines, and Allegheny Airlines.

Widespread use of discount fares has been cited as a main reason for the improved airline profits.

American earned $43.9 million ($1.32 a share fully diluted) in the second quarter, some 39 percent above 1977 second-quarter earnings of $31.5 million (93 cents). Revenues rose 18 percent from $581.1 million a year to $688.2 million in the latest period.

First-half net income was $36.9 million ($1.07) on $1.285 billion in revenues compares with 1977 first-half net income of $29.9 million (93 cents) on $1.104 billion in revenues.

Braniff net income rose 14.9 percent in the second quarter to $11.2 million (56 cents a share) in the second quarter from $9.7 million (49 cents) a year earlier as revenues increased by 22.9 percent to $236 million from $192 million.

First-half net income was $20.1 million ($7), a 22.5 percent gain over 1977 first-half net income of $16.4 million (82 cents). Revenues of $454.1 million were 21.5 percent more than the 373.9 million posted a year earlier.

The chemical giant Du Pont Co. reported a 20 percent increase in net income from the 1977 second quarter to the latest period but another major force in that industry, Dow Chemical Co., said its net income dropped by $500,000 between the 1977 and 1978 second quarters.

Du Pont reported preliminary earnings of $191 million ($3.92 a share) for the second quarter compared with $161 million ($3.28) a year earlier on an 11 percent increase in sales to $2.731 billion from $2.471 billion.

First-half net income rose 29 percent to $359 million ($7.37) from $282 million ($5.73) as sales increased by 11 percent to $5.275 billion from $4.742 billion.

Du Pont Chairman Irving Shapiro said traditionally strong second-quarter gains were offset partly by "some deterioration in commodity chemicals profitabiliy, and nonrecrurring charges of 35 cents per share resulting from duscontinuance or interruption in the manufacture of certain products."

Dow Chemical earned $154 million (84 cents a share) in the second quarter compared with $154.5 million (83 cents) a year ago, although sales increased by 12 percent to $1.75 billion from $1.56 billion. Per-share earnings increased despite the drop in net income because fewer shares were out.

First-half net income decline 7 percent to $283.5 million ($1.55) from $306.2 million ($1.65) in the first half of 1977. Sales were 10 percent higher at $3.4 billion compared with $3.09 billion.

Although operating rates improved in the spring as the volume of shipments increased markedly over the results of a year ago, "Chemical prices are not increasing at the same rate that our costs have been going up," said G. H. Williams, Dow's financial vice president.

Two manufacturers of computers listed improved earnings yesterday.

HONEYWELL INC. had second-quarter earnings of $44 million ($2.06 a share), up 49 percent from the $29.6 million ($1.41) earned a year earlier.

Worlwide sales, rental and service revenues increased 22 percent to $861.2 million from $705.2 million.

For the six months of 1978, Honeywell's total revenues were $1.65 billion compared with $1.36 billion a year ago. Six-month earnings totaled $79.4 million compared with $60.5 million the previous year. Earnings per share in the first half of 1978 were, $3.72 compared with $2.88 in 1977.

SPERRY RAND CORP. reported its 25th consecutive quarter in which earnings exceeded the preceeding year's comparable quarter.

Company officials said earnings for its first quarter ended June 30 were $45.1 million ($1.29 a share) compared with $37.5 million ($1.08) for the same period in 1977.

Quarterly revenues of $972.5 million were 1.75 percent higher than the $827.8 million registered in 1977, the firm said.

Inland Steel Corp. profits increased to $46.2 million ($2.23 a share) in the second quarter from $40.3 million ($1.97) a year earlier and to $70.3 million ($3.39) in the first half from $52.4 million ($2.54).

Sales increased in the second quarter to $837.5 million from $700.5 million a year ago, and to $1.594 billion in the first half from $1.328 billion.

Bendix Corp.'s third-quarter profits jumped 17 percent from the same quarter last year, primarily because of the firm's strong aerospace-electronics and shelter business, Bendix reported yesterday.

Earnings were $39.8 million ($1.74 a share) for the April-July period compared with $34 million ($1.52) a year ago. Revenue of $984 million in the most recent quarter was up 12.4 percent from $875 million a year ago.

For the first nine months of the Bendix fiscal year, revenue totaled $2.7 billion compared with $2.4 billion in the same period last year. Profits were $100.1 million ($4.45), up from $90.7 million ($4.06).