Here are the persons that took photos of people at Auschwitz and how (were they allowed to/ and the circumstances

There are four categories of photos that were taken in lagers.

Photo ID of the prisoners. In many camps, including Auschwitz, pridoners that were accepted in the camp were photographed. People who were gassed on arrival were not even recorded, but those who were temporarily spared for work of for serving as experimentation stock, as well as non-Jewish inmates, were recorded, and in Auscwitz, Dachau, and other camps the record included a photo ID.

Photo taken in secret. Sometimes the Allies and the Resistance movements were able to smuggle in a camera handing it to a prisoner. There were indeed contacts between various resistance movements inside and outside the camps. The cells inside the camps had several tasks, one of which was documentation (the others were trying to organize the rare escape attempts, setting up rebellions and sabotage of the industrial production, circulating news, managing secret radio receivers, etc.). The photos were taken hurriedly and then smuggled back out because any prisoners caught with a camera or any photo material would be tortured and killed. The pic above documents the experiments on an inmate at Ravensbruck, whose legs were deliberately infected with different bacteria. It was taken by a fellow inmate who had received a camera through a German resistance movement. Occasionally, clandestine photos were also taken in secret by other witnesses. We have a handful photos of the death marches taken by norman citizens from their windows while the column walked past their houses.

Photos taken by the guards themselves. Guards owned cameras and would sometimes casually take photos of their job. One of the largest bodies of images on the lagers are the photos taken by Spanish photograper Francesc Boix Campo. He was a former Republican soldier arrested in France and transferred to Mauthausen. There he was recruted by a camp officer to take the photo ID of the prisoners as well as documenting the work of the camp. Boix managed to make copies of the most relevant photos he took and other inmates would hide them in various locations. When liberation of the camp became inevitable, the camp commandant ordered the photos to be destroyed, but those sectetly hidden by Campo and his comrades were saved. These images were key in documenting the brutality of the camp. I strongly suggest watching The Photographer of Mauthausen, a Spanish movie on the life of Francesc Boix Campo, and one of the most realistic films on nazi Lagers.

Photos taken by the liberators. When the Allies reached a camp, one of the first thing they did was thoroughly document what they found. The avove photo was taken by a Soviet photographers immediately after Ravensbruck was liberated, and depicts a Soviet female soldier talking with a group of inmates. Both Soviets and Western allies took a large number of images (both photos and film) of all major camps they reached.