The comparisons between the albums are both poignant and obvious, as they juxtapose the comfortable daily lives of the guards with the horrific reality within the camp, where thousands were starving and 1.1 million died.

For example, one of the Höcker pictures, shot on July 22, 1944, shows a group of cheerful young women who worked as SS communications specialists eating bowls of fresh blueberries. One turns her bowl upside down and makes a mock frown because she has finished her portion.

On that day, said Judith Cohen, a historian at the Holocaust museum in Washington, 150 new prisoners arrived at the Birkenau site. Of that group, 21 men and 12 women were selected for work, the rest transported immediately to the gas chambers.

Those killings were part of the final frenetic efforts of the Nazis to eliminate the Jews of Europe and others deemed undesirable as the war neared its end. That summer the crematoriums broke down from overuse and some bodies had to be burned in open pits. A separate but small group of known preliberation photos were taken clandestinely of those burnings.

Auschwitz was abandoned and evacuated on Jan. 18, 1945, and liberated by Soviet forces on Jan. 27. Many of the Höcker photos were taken at Solahütte, an Alpine-style recreation lodge the SS used on the far reaches of the camp complex alongside the Sola River.

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Though they as yet have no plans to exhibit the Höcker album photos, curators at the Holocaust Memorial Museum have created an online display of them on the museum’s Web site (ushmm.org) that will be available this week. In many cases they have contrasted the Höcker images with those from the Auschwitz Album. In one, SS women alight from a bus at Solahütte for a day of recreation; meanwhile, in a picture from the Auschwitz Album taken at about the same time, haggard and travel-weary women and children get off a cattle car at the camp.

Museum curators have avoided describing the album as something like “monsters at play” or “killers at their leisure.” Ms. Cohen said the photos were instructive in that they showed the murderers were, in some sense, people who also behaved as ordinary human beings. “In their self-image, they were good men, good comrades, even civilized,” she said.

Sarah J. Bloomfield, the museum’s director, said she believed that other undiscovered caches of photos or documents concerning the Holocaust existed in attics and might soon be lost to history.

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The donor, who had asked to remain anonymous, was in his 90s when he contacted the museum, and he died this summer. He told the museum’s curators that he found the photo album in a Frankfurt apartment where he lived in 1946.

The photos of the Auschwitz Album were discovered by Lili Jacob, a Hungarian Jew who was deported in May 1944 to Auschwitz, near Krakow in Poland. She was transferred to another camp, Dora-Mittelbau in Germany, where she discovered the pictures in a bedside table in an abandoned SS barracks.

She was stunned to recognize pictures of herself, her rabbi and her brothers aged 9 and 11, both of whom she later discovered had been gassed immediately after arrival.

Höcker fled Auschwitz before the camp’s liberation. When he was captured by the British he was carrying false documents identifying him as a combat soldier. After the 1961 trial of Adolf Eichmann in Israel, West German authorities tracked down Höcker in Engershausen, his hometown, where he was working as a bank official.

He was convicted of war crimes and served seven years before his release in 1970, after which he was rehired by the bank. Höcker died in 2000 at 89.