Editing Kerrison Predictor (section)

==US service==
Although it was more accurate than the Kerrison predictor, Sperry was unable to keep up with production of its more expensive and complex M-7 director.{{sfn|Mindell|1995|pp=108–113}} In September 1940, [[George Marshall|General George C. Marshall]] asked the British for the loan of four Bofors 40&nbsp;mm guns with Kerrison Predictors for testing.

During testing the Kerrison Predictor provided accurate fire control to a range in excess of {{convert|1500|m|abbr=on}}, and the Bofors gun was reliable. In the fall of 1940, the [[Ordnance Department]] standardized the Kerrison Predictor for use with their 37&nbsp;mm gun. By February 1941, the U.S. Navy had adopted the Bofors for use on their ships. To ease production problems, the Army reluctantly standardized on the 40&nbsp;mm in February 1941; the U.S. was building the Bofors for the British under the [[Lend-Lease]] Program.

The Predictor's plans were passed to [[Sperry Corporation]], who were just commencing production of their own complex high-altitude system, the [[M7 Computing Sight]], and had no excess capacity to produce the new design as well. Instead, they completed changes needed to adapt the Predictor to U.S. production and sent the plans back to the Army for production elsewhere. In December 1940 the [[Singer Corporation]] was contracted to produce 1,500 predictors per month<ref>{{cite web |title=M5 Director, from Singer in World War II, 1939-1945 |url=http://home.roadrunner.com/~featherweight/m5direct.htm |website=Wayback Machine Internet Archive |archive-url=https://web.archive.org/web/20090604094416/http://home.roadrunner.com/~featherweight/m5direct.htm |access-date=15 November 2020|archive-date=2009-06-04 }}</ref> to equip the Army's existing 37&nbsp;mm guns while production of the 40&nbsp;mm Bofors was ramped up. Two models were built initially, the M5 running on US-standard 115&nbsp;V 60&nbsp;Hz power,{{sfn|TM|1944|p=6}} and the M6 for British use, running on 50&nbsp;V 50&nbsp;Hz power.{{sfn|TM|1944|p=6}} The original M5 was designed to use an external [[torque amplifier]], which added to the complexity. This was addressed in the M5A1, which used a more powerful ball-and-disk system that eliminated the need for an external amplifier.{{sfn|TM|1944|p=7}}

To produce the devices rapidly enough, Singer implemented massive changes in the company, including building new factories and the switching of a foundry from steel to aluminium. Production did not begin until January 1943, but the entire order was filled by the middle of 1944. For a brief time, some of the U.S. Army's Bofors guns were equipped with the Sperry M7, but these were replaced in the field as soon as M5s became available.{{sfn|Mindell|1995|pp=108–113}}<ref>{{cite web|url=http://home.roadrunner.com/~featherweight/m5direct.htm |title=Director M5 |access-date=2008-05-17 |url-status=dead |archive-url=https://web.archive.org/web/20090604094416/http://home.roadrunner.com/~featherweight/m5direct.htm |archive-date=2009-06-04 }} (Excerpt from {{cite book|title= Singer in World War II, 1939-1945|
url={{Google books|cbMUHoH12csC|Singer in World War II, 1939-1945|page=|keywords=|text=|plainurl=yes}}|publisher=[[Singer Manufacturing Company]]|date=1946}})</ref>

With aircraft speeds increasing dramatically during the war, even the speed of the Kerrison Predictor proved lacking by the end. Nevertheless, the Predictor demonstrated that effective gunnery required some sort of reasonably powerful computing support, and in 1944 [[Bell Labs]] started delivery of a new system based around an electronic [[analog computer]]. The timing proved excellent; late that summer, the Germans started attacking [[London]] with the [[V-1 flying bomb]], which flew at high speeds at low altitudes. After a month of limited success against them, every available anti-aircraft gun was moved to the strip of land on the approach to London, and the new sights proved to be more than capable against them. Daytime attacks were soon abandoned.

Long after the war, U.S. M5s started appearing in surplus shops in the late 1950s. [[John Whitney (animator)|John Whitney]] purchased one (and later a Sperry M7) and connected the electrical outputs to [[Servomechanism|servos]] controlling the positioning of small lit targets and light bulbs. He then modified the "mathematics" of the system to move the targets in various mathematically controlled ways, a technique he referred to as ''incremental drift''. As the power of the systems grew, they eventually evolved into [[motion control photography]], a widely used technique in [[special effects]] filming.<ref>{{cite magazine |magazine=Animation World |date=5 August 1997 |title= The Whitney Archive: A Fulfillment of a Dream |first= Michael |last=Whitney |url=https://www.awn.com/mag/issue2.5/2.5pages/2.5whitneyarchive.html}}</ref>