Arizona republican., 1917-05-27
AR IF HALF
 TOWING TOLO
 TO C[UbMEN

V OEOU1uIIIv | Those who see pictures reproduced a in newspapers and other publications have but scant idea how cuts them selves are made For that reason the address of S. Harry Robertson. of the Phoenix Engraving company, delivered on Friday at the Rotary club meeting, is of particular interest. He told of the growth Of the business of the invention ; of the half tone and showed examples of work in all stages. His interesting and instructive paper was as follows: MT. Chairman and fellow members
 of the Rotary club.
 In presenting for your consideration today q brief exposition of the photo engraving methods in general use at
 this time, 1 feel considerable diff , dence in attempting to fix authoritatiV ely the exact rules which govern the
 production of modern printing plates because in the first place the exigen-
 eies of business have gradually blunted
 the sharpness of many salient theo
 retical points and reasons and l Cir common with many others) have grad ually become routine 'doer''- more or less unconscious cog in the com mercial machine This foreWord there fore must really be taken by you as an
 excuse for my ability to fix dates with exactituGe, more specially as they occur r in connection with the historical DOT
 ton of this talk.
 , l feel pretty certain however. that l it was in 1868 that the first photoen- , graving which was the direct foierun , Ter of what we now Gin trade) term
 "halftone" made it's appearance. as the
 result Of experiments by a certain Gen.
 Frederick w. von Egloffstein, a Prus- , sian Jew. The real genesis of the pro- cess dates back still further. however,
 even to 1924 when Niepce produced the
 first metal printing plate of Cardinal Amboise
 Almost everyone who has any print ing work done is familiar with the term "half-tone' as descriptive Of q certain type of printing plate, but the name is really very poor one so far I as descriptive interpretation goes. Half ! tone. really means a shade tor tone) 5 midway between black and white in reality the modern photo engraved \ plate represents rot only black and \ white but an innumerable quantity of ' intermediate tone lying between. Tine E French term of "simil gravure" ex- \ presses the idea much better although | the word ''halftone'' seems to have been | so thoroughly. adopted in the language E that even the French themselves now E refer to it as 'Demiteirte.''
 One is tempted to enter at length into the historical phase of the process and | endeavof by refreshed memory 60 sup D ply a list and brief resume of the vari- ous steps which have led to the present state of the art, but neither time nol the probable temper of my audience | will allow, it is advisable therefore that we hasten on to a consideration of the process as it StandS today.
 Even the most casual observer will | have noticed that a halftone engraving ' represents picture made up of q curi- ous checkerboard pal sern which runt from a series of needl like white dots in the deep shadows up through vary | ing shapes and sizes to series of deli cate black dots in the high lights. The presence of these dots is what allow: of the plate being printed upon white paper and are produced by the inter position of a ruled crosslne screen i'm mediately in front of the photographic ' plate when the negative is being made \ IL will perhaps serve to create cleare understanding if we take up each stel
 of the process in logical sequence. Let us assume that we are required
 to produce "halftone" plate from \ Jortrait print of any one of the man. | good looking and expressive counten
 ances I see now present.
 Fl The regular photographic portrai \ print is fastened up in front of th' \ lens of the process camera and iilu \ mined by powerful arc lamps. A mega E tive is then made (by means Of the ols \ wet 'nlate method generally but thi
 negative differs vastly from the reg ' ular negative made by the regula ' photographer Directly in front of tn II sensitive plate and almost touching U fc nlaPaJ clear pl9cS nlatp | which has been accurately ruled | series of close parallel lines crossin | each other al right angles These rule
 lines are filled in with a black sub | stance which is absolutely opaque con
 sequently all that is left is series 0 \ clear glass squares.
 These cross line screens are manu ! factured in great variety of ruling \ which run all the way from 90 to tn \ inch up to as many as 200 to the inc although this is not limiting mum | Der by any means because screens hay \ been ruled with as many as 400 line \ to the inch.
 The ruling in most general use is ap I proximately 133 line. coarser than thi 1 the dots in the finished engravin - are too apparent, but the plate may D - printed on softer and poorer pape
 which with a finer mesh than 133
 
 is required.
 IL will be understood that when th cross line ruled screen plate is inter | posed before the plate and in contat I with it that one could only obtain | negative through the clear squares s
 that it would appear in a print as | portrait seen through q black eros line net but that the image would oth erwise be just the same, i. C.. some { the portions seen between the scree
 lines would be white, some black, >an some of all varying tones.
 If however, the ruled screen be SCI arated slight distance from the SCI sitive plate then an altogether diffel ent effect results for each mnu clear square acts just like a small Ter
 and transmits a beam of light Of vary ! ing intensity on the sensitive plat
 with the result that some of the bean l (the bright ones) form (upon deve opment) large dots, while. where u
 light had been poor, as in the shadow
 of the picture the dots formed are vel
 small. It will be understood therefor ! that intermediate brightness wou ! therefore form intermediate sized dot
 Briefly. the portrait no longer exists ;
 d collection of shades or 'ints but on
 as a collection of dots of varying size It is to be regretted that I have bee ! unab ole to prepare lantern slides Whit
 might graphically portray this mo
 singular and remarkable difference, b | I have here upon the table assemble
 the various steps of the process so