The photographs are blurry, composed hastily and taken surreptitiously, sometimes with heads or objects in the foreground obscuring part of the view. But Holocaust historians say the imperfect pictures, discovered last month in a Polish attic decades after their creator died, are nonetheless priceless. They are the only known photographs from inside the Warsaw Ghetto Uprising not to be taken by Germans. The photographs will form part of an exhibition devoted to the 80th anniversary of the uprising, to be held in April at Warsaw’s POLIN museum of Jewish history. The hunt for the photographs began last year, when curators...