- FEI 000: Belonging to the Subject, not further Classified
- FEI 001: Precision Engineering; Precision Mechanics; Apparatus Engineering
- FEI 100: Precision Apparatus EngineeringHandguns see WEH 630
- FEI 200: Office Machines; Office Technology
- FEI 250: Technical Toys; Toy Fabrication; Modelling Technology
- FEI 295: Doing Handicrafts; Do-It-Yourself; Home Improvement
- FEI 400: Technical Optics (Construction, Production, Processing etc.), Microoptics
- FEI 410: Optics: Components and Systems (Lenses, Objectives, Shutters, ...; Optical Glass)Physical Aspects see PHY 392
- FEI 430: Precision Optics; Ophthalmic Optics; Spectacles
- FEI 440: Beam Waveguides; Fiber Optics
- FEI 450: Optical Instruments in General
- FEI 454: Telescopes; Binoculars
- FEI 458: MicroscopesMicroscopy see PHY 130 ff
- FEI 462: Spectroscopic Instruments; Optical Interferometers
- FEI 454: Telescopes; Binoculars
- FEI 490: Others on Technical Optics
- FEI 410: Optics: Components and Systems (Lenses, Objectives, Shutters, ...; Optical Glass)
- FEI 500: Film and Photographic Technology
- FEI 600: Photography in General; Photographic Methods
- FEI 601: Digital Photography
- FEI 605: Exposure Technique; Focus; Photographic Failures
- FEI 610: Black-and-White Photography
- FEI 615: Colour Photography
- FEI 620: Large-Format Photography
- FEI 625: Small-Format Photography
- FEI 630: Microphotography
- FEI 635: Macrophotography (Close-up Photography)
- FEI 640: Stereophotography; Stereoscopy; 3D Imaging
- FEI 645: Instant Photography
- FEI 650: Scientific Photography in General
- FEI 655: High-Speed Photography
- FEI 660: Infrared Photography
- FEI 665: Other Photographic Methods
- FEI 680: Photography in Specific Disciplines (Landscape Photography, Underwater Photography, ...)
- FEI 601: Digital Photography
- FEI 700: Photographic Apparatus; Projectors and Auxiliary Equipment
- FEI 800: Film Technology; Cinema Technology
- FEI 900: Reproduction Technology; ReprographyPrinting see IND 920 ff