|Blodgett ship camouflage plans (redrawn)|
This full document can be accessed here at the MIT library website. His hand-drawn colored diagrams of camouflaged ship models are somewhat imperfectly rendered, so I have redrawn them on computer. A more serious problem is that the color swatches (a key to the colors applied to the ship models) were apparently made with opaque watercolor (gouache), and some of the colors have dramatically changed with the passage of time. So the colors in my reconstructions may differ considerably from the originals. Also, as Blodgett mentions in his text, he restricted his experiments to those that made intentional use of perspective distortions or forced perspective (aka "false perspective").
Using a ship camouflage testing theatre that, at the end of the war, was given to MIT by Boston-area camouflage artists (he includes two photographs of it, reproduced below), he determined that average course estimation errors could sometimes be substantial. To date, this is the most persuasive proof that not only was dazzle camouflage effective in diverting the aim of the U-boats, it was far better than anyone thought.
|Ship Camouflage Testing Theatre (c1919)|
These notes were originated in support of efforts to avoid course deception effects in the painting of aircraft. They constitute a brief discussion of some of the principles employed in the design of the course-deception patterns and type-deception patterns formerly incorporated in the painting of surface ships as a defense against submarine and surface ship attack directed by visual sightings. Although technical developments have eliminated these measures from naval practice, the concepts from which they were developed are not without present value. The notes are reported herein primarily because no comparable written material on this subject appears to be available.
Several effective patterns for the painting of surface vessels were devised in World Wars I and II to decrease the probability that the true course and speed of the ship would be correctly estimated by an observer at sea level. It is the purpose of this report to discuss some of the principles upon which the design of these patterns was based.
BASIS OF COURSE ESTIMATION
Successful estimation of the course of a vessel involves a special mental process in the recognition category: When some object which might be a ship is visually perceived, the observer is required to search his memory and generate within his brain visualizations of known ship-types at various headings in order to compare these visualizations with the appearance of the object. When the correlation between the apparent object and one of these visualizations is sufficiently good the observer experiences a sense of recognition and course estimation. This mental process, usually subconscious and rapid, requires familiarity with the appearance of ships and, of course, improves with experience due to the accumulation of memory. If visualizations at more than one heading correlate closely with the appearance of the unknown object, course estimation is ambiguous; accuracy is possible only if there is a rapid rate of change of correlation between the appearance of the unknown object and a series of visualized ship headings. Any factor causing the appearance of the object to fail to correlate with visualizations based upon memory of known ships will inhibit or prevent recognition and course estimation. It is not surprising, therefore, that several types of course deception pattern techniques have been evolved. These can, however, be classified into two main groups, which might be termed confusion measures and falsification measures, respectively, for lack of more standardized terminology. These two categories will be discussed separately in the following sections.
As previously stated, any factor causing the appearance of an unknown object to fail to correlate with visualizations based upon memory of known ships will inhibit or prevent course estimation. Two classical methods for achieving confusion by means of paint have been called dazzle and low visibility, respectively.
The weird and garish dazzle designs so common on ships plying the North Atlantic during World War I have long disappeared from the seas, but pictures of them are easily available and universally excite curiously concerning the origins, the functions, and the basis for their design. All dazzle patterns sought to give the ship an unrecognizable appearance from a "periscope viewpoint." Almost any large discordant pattern departing markedly from all natural lines of a ship can accomplish this confusion objective. Each of the artists who conducted dazzle studies at model scale evolved favorite pattern-types, all of which served to produce course deception by confusion. The best of the dazzle patterns, however, sought to incorporate false perspective as a further course deception feature; perspective distortion as an independent course deception measure will be discussed in a later section.
Low visibility painting schemes for ships are still in use and are intended primarily to reduce the probability of the presence of the ship being visually detected. This is usually accomplished to some useful degree, but every low visibility treatment is a compromise and approaches true concealment within only a very narrow gamut of lighting and viewing conditions. At other times, portions of the vessel may be difficult or impossible to see, but other parts are readily visible. When this situation prevails, recognition of the ship may be impossible and its course may be difficult to estimate. The low visibility paint is then serving to provide course deception by confusion.
Since any factor causing the appearance of an unknown object to fail to correlate with the correct visualization of the ship being observed may lead to an erroneous course prediction, falsification of several kinds were employed in ship camouflage. Included in this category of course deception measures are disguise, false cues, false perspective, and symbolic patterns. Many ingenious falsification measures have been devised, but this report will mention only a few examples.
Disguise took many forms and was more commonly employed for reasons of type deception than course deception. False superstructure was added, for example, to tankers to make them resemble freighters, transports, or even warships, and in so doing reverse bow and stern in order to add an element of course deception.
False Cues included such devices as a bow wave painted at the stern of the ship, or a pint pattrn on or near the stack of a vessel intended to make the stack appear to learn toward the bow rather than the stern.
False Perspective was not confined to dazzle patterns. False superstructures and false water lines were employed to produce an untrue illusion of distance and to produce errors in stadiometric ranging through a periscope. False water lines tilted slight from bow to stern gave to the ship the illusion of a false heading. An analogous effect was sometimes achieved by the use of non-parallel bands of paint on the sides of vessels having multiple decks, thus inducing a false convergence relation.
Symbolic Patterns saw relatively little use in naval camouflage but they are extensively used as a type of "falsification measure" in many forms of art and design. A recent example is found in the current styling used by a certain automobile manufacturer, who says that his cars appear to be in motion even when standing still. This is achieved by an overall wedge-shaped motif high at the rear and tapering to a low point in front, suggestion of the configuration of recent high speed aircraft or of an arrow point. Arrows or chevron markings are often used to indicate direction.
|books & historic prints and photographs|