Public domain photos

The image shows an open book with a drawing on it. The book is filled with lines and text, and at the bottom of the image there is a watermark. The drawing appears to be a photo of an aperture, with the lines and numbers indicating the angles of the aperture.

The image shows an open book with a drawing on it. The book is filled with lines and text, and at the bottom of the image there is a watermark. The drawing appears to be a photo of an aperture, with the lines and numbers indicating the angles of the aperture.Open in library