Douglas A. Kerr
Electrical engineer and absolute camera and lens specialist based in the United States. Operator of the website www.dougkerr.net and author of countless in-depth technical documents. Doug has provided great support in the field of USM and Micro USM autofocus systems as well as astigmatism and spherical aberration.

Horst Schröder
Physicist and owner of Germany-based optical engineering company Horst Schröder Optikentwicklung. Thank you for providing descriptions about zoom lenses and for literature recommendations.

Jin Takayama
Lens design specialist from Japan. Operator of the websites www.lensreview.xyz (Japanese) and www.lensreview-en.xyz (English). Mr. Takayama has been of great help discussing various optical questions and providing detailed resources.

Kaan Turan
Qualified optical engineer from Turkey. Mr. Turan was very kind to provide an essay about optical fundamentals and aberrations.

Katie Schwertz
Lens design engineer at Edmund Optics, a US-based leading supplier of precision optics and optical components. Thank you Katie for creating Zemax simulations on achromatic lenses and for discussing various other optics-related topics.

Peter Bober
Engineer and assistant professor at the Technical University of Košice, Slovakia - Faculty of Electrical Engineering and Informatics - Department of Electrical Engineering and Mechatronics. Mr. Bober provided a detailed explanation on the operation principle of the EMD stepper motor.

Rainer Hönle
Physicist and Canon lens repair specialist from Germany. His website www.gletscherbruch.de, among photo-galleries, shows electromechanical parts of Canon cameras and lenses. Rainer is also the inventor of a specialized polymer-based camera sensor cleaning solution. Check out the website www.sensor-film.com for more information. Thank you for various conversations about Canon USM and Micro USM autofocus motors, and about anti-reflective coatings.