The US "optics crisis" (1943) The following quotes are excerpts authored by D.M. Mattox (In his book "The foundation of vacuum coating technology" (2003), Mattox - a B.S. degree in Physics from Eastern Kentucky State University and M.S. degree in Solid State Physics in 1960 from the University of Kentucky - describes some of the techniques used by the Germans), which demonstrate what had led to the German's advanced optics. Some of the corresponding German patents were granted around 1938/1939, declared to be military secrets right away and not published, where relevant developments and inventions/patents that lead to sophisticated coating/processing of lenses - used in cameras, gunsights, film projectors and other applications - are listed by Mattox: During the African campaign the shortcomings of the US tanks' optics had alarmed US officials, so that - as a result - the US put quite some effort into overcoming what I would call the "optics-crisis" of 1943. Later in the war, Sherman tank optics were somewhat better (as magnification levels increased), but still did not match the quality of most (if not all) of the German optics. The US Army obviously knew that at least proper coating appeared to be vital for getting improved optics, thus they sponsored the conference. Pre-processing the lenses (which the Germans did it seems) may have been vital too, but I don't know if that had been part of the Committee's evaluation, too. The question is what the particular findings of this conference were, and when (and how) that showed on actual production models of tank optics. Afaik, even until 1944/45, US tank optics remained inferior, despite the introduction of optics with way higher magnifications (5x). The Russians, in turn, tried to copy the German optics, and at least the ones employed in IS-2 tanks were really good (astounding max range). Even though it looks like the author, who is obviously a scientist/engineer, he seems to have randomly collected and listed coating attempts, patents and innovations, and he actually outlines - almost in shorthand format - what processes were known in the western world, and what other processes - which either just remotely dealt with coating or which could have also led to a proper knowledge level in the optics field - were known. I am not a physicist, nor a chemist or photographer/photography engineer, but as I understand it, the coatings provide for more clarity by allowing more rays of light to pass through a lense (or set of lenses, which you need for higher magnification levels), by applying such anti-reflection coating: Basically, without coating, the more lenses (that had been produced in the old fashioned way) the Allies put into a telescope (to receive a higher magnification), the more clarity got lost (10% with each lense). I've read that a 40% loss of clarity definetly impacts usability, so a US 4-lenses-system wouldn't have been too helpful for a tank gunner. The Germans, in turn, were using 4-lenses in their systems without any problems. Also: the more lenses the more restricted the field of view (12° FOV for many US gun optics only, while German optics had 25°). So, generally, German tanks in Africa had partially inferior (Pz.III?) magnification, the same (PzIV?) or even better magnification (Tiger?), but absolutely superior clarity, and twice the field of view compared to Allied systems. After the Western Allies had upped their magnification levels to 4x and 5x (1943?), the Germans followed with the introduction of 4x and/or 5x (Panther) magnifications, at some point, which then offered even more superior optics, as their 4-lenses-systems (for example) only lost 16% of clarity, instead of 40% (on the Western Allied systems). Zeiss used a special technique developed in 1938 which involved an AR coating on the lenses, reducing the loss (of clarity) per lense to 3-4%, which allowed for the production of sighting systems with 4 lenses and more, while maintaining the clarity of a Western Allied gunsight that carried 1 or 2 lenses only. The Western Allies didn't know about that production method until after the war (I am not sure about the Russians). The footnotes in Mattox' work: Some German historians suspect that the Japanese military got all infos regarding coating and lense technologies, along with blueprints of military applications and weapons shortly before Germany was forced out of the war. Some tech-transfer attempts (like a disassembled Me 262 + blueprints aboard a submarine, which surrendered on the Atlantic Ocean - after is had received the radio message that Germany had surrendered, leading to the 2 japanese officers - ordered to escort the precious cargo - committing suicide aboard) either did not make it to Japan, or took several attempts (even with rumors about an alledged long-range flight of the only (and famed) German long-range bomber using the route over Syberia). Whatsoever, the Japanese became the leaders in the camera sector by using the German technologies as foundation, most likely, as Canon and Nikon did not even attempt to acquire the camera (and lense) patents, since they must have had all the infos about the manufacturing process, already. Mattox seems to think that the optics technology was passed, but I can't remember whether he mentioned it explicitly, or not. (I'd have to dig for his thesis). If not, he must have omitted his personal thoughts, as there is no particular evidence to prove that particular transfer, yet.