Book revietus

Perpetuating a polluted problem

'Health hazards of VDTs?' Edited by Brian Pearce, Wiley, 1984, pp 344, £16.50 This is a collection of papers pre- sented at seminars on the above topic organized by Lon_ghborough University mainly for the good of mankind but, in view of the financial stringency bestriding institutions of learning and the large fee charged for attendance, not only for that purpose. That we are not likely to be dealing with unadulterated health hazards, alleged or other- wise, is stated clearly by Miss S. McKechnie. She says that the pres- sures on U'ade unions due to prob- lems of job satisfaction etc on the one hand and information on health effects on the other cannot be separated.

One would have though that health hazards are amenable to a cool, calm, clinical or scientific appraisal but the above concoction of socio-economic and ergonomic factors makes it hard to be objec- tive. It is sad to have to report that even an apparently purely clinical paper like that by Dr Milton Zaret contributes to one's frustration. This gentleman asserts that he knows signs specific to VDT-induced cataracts. None of his peers has come forward in corroboration of his claims. Hauled before a New York court, he failed to convince experts about some of the cases regurgitated in this book, and at least one of the cataracts he parades predated the use of VDTs. Although all this was public before these seminars were held, he was an invited speaker. All credit to Pro- fessor E. Grandjean for dazing to mention the word 'statistics'.

This is not to say that all the papers are one-sided or that work-

ing conditions are not a cause for just concern. But why single out VDTs? Why not typists, laxha operators, plumbers, dentists or teachers? Could it be that the allegedly inseparable ergo-social

wolf has gobbled up the clinical innocent? We shall never know because the VDT health hazard problem has been polluted for all' time. As this book demonstrates.

Robert Weale Ins~mte of Ophthalmology

Univer~ of London

Where engineering meets colorimetry

'Co lour s c i e n c e in t e lev i s ion a n d d i s p l a y s y s t e m s ' W.N. Sproson , A d a m Hilger , 1983, pp 221, £20.00 This is not a review written by an engineer; it is intended to point out the relevance of this book to indivi- d,,,,l~ who are concerned with colour science and its application to colour television systems.

As is the case for almost every book concerned with colour the author is faced with the dilemma of whether to describe the CIE system or assume prior knowledge of the system by the reader. In this instance prior experience is not assumed, and the first chapter con- cisely precises the subject in a manner superior to most texts, and includes coverage of the more recent and often neglected CIE Luv and CIE Lab systems. However, the rate at which new concepts are pre- sented is high and the newcomer to the subject would do well to linger over each section.

The first chapter sets the for- mat for the rest of the book, with high information rate but well pre- sented information throughout. Appendices and a very useful glos- sary of terms do much to unclutter the text. However, the overall layout of the chapters and their sections

could be more logical and conse- quently more easy to follow. It is somewhat bewildering that the 'aims and objectives in colour reproduction', along with a block schematic of a model of a television system, do not appear until the final chapter. As the book attempts gradually to put together the entire system, the model should perhaps appear in simplified form within chapter two, allowing the sub- sequent chapters to progress through the system, elaborating upon the discrete elements. As it is, the book tends to oscillate between input and output requirements which, although inseparable in practice, could be more isolated in the text to avoid confusion.

What then does the book con- tain? After the introduction, the requirements for cross-coupled col- our channels (matrix) is explainod with the aid of matrix algebra. The non-specialist might be deterred by the algebra, but it is not essential for an appreciation of the concepts, and thankfully the more tedious cal- culations have been displaced to an appendix. The worked examples using the CIE 14 test colours make it easy to appreciate the difference between the American NTSC and British PAL standards. It is certain that the section on colour telecine

DISPLAYS. OCTOBER 1984 251

machine will be of value to a wider audience than television engineers particularly with the increased use of colour computer graphics to dis- play material which was previously presented in printed form.

Chapter three deals with the broadcast of television signals and is primarily written for the specialist. The colorimetrist would benefit from grasping the concepts involved but several readings and the help of a tame mathematician will possibly be necessary for a full appreciation of the subject. The presentation of the material is very good. The reader might easily give up at this chapter, expecting even more specialized material to follow, but this is not so. Chapter four deals with the optical components of tele- vision cameras and is both easy to read and informative, explaining not only the problems encountered but comparing the merits of alternative solutions.

That the book is intended for the specialist becomes apparent in chapter five which considers colour display tubes. The various types of tubes available are considered in only superficial detail for complete- ness rather than to inform. The non-

specialist may wish to consult an alternative text but, alas, no refer- ences are given. The latter part of this short chapter includes a con- cise introduction to the transfer characteristics of display devices which seems to be somewhat out of context and would perhaps have been better in chapter six. Sections on spectral power distributions of display tubes, though short, are par- ticularly well illustrated and enable the discussion on the need for a standardization of primary phos- phors to be appreciated.

Chapter six is an interesting mix of psychophysics and its rele- vance to bandwidth inves~'gations in televim'on. Again matrix algebra appears, but only temporarily, and precedes some interesting plots of constant luminance in CIE space which will be of interest to the colorimetrist and VDU operator.

Chapter seven has already been mentioned as containing infor- mation which perhaps should have appeared earlier in the book. This extensive chapter contains a wealth of information on various topics bundied-up together. The sections on the effects of gamma, and those related to viewing and illumination

conditions are well worth a read. But, although adequately consider- ed, the photometry of television cameras and quantum considera- tions appear somewhat out of con- text. The mathematical model of a colour television which concludes the chapter builds upon the data presented earlier in the book, and the author should be congratulated for his ability to portray a worked example in only a few pages, bring- ing the whole subject matter to such a simple and neat conclusion.

In summary, by the use of numerous illustrations and concise text the author has covered the major areas of colour television in a remarkably slim volume, perhaps too slim for the uninformed reader. Although the volume is written primarily for television engineers it is certainly of interest to anyone interested in colorimetry. I fear this valuable book will appeal to only a limited audience as the subject matter fails between engineering and colorimetry.

John Laycock Royal Aircraft Establishment

Fambomugh

e

microprocessors and mlcn ystems

the authoritative internation journal on microcomputer technology and applications for designers

Special individual subscription rate

Further details and subscription rates

Christine Mullins Butterworth Sclentil - - Journals Division PO Box 63 Westl BuryStreet Guildford Surrey GU2 5BH I~ngland Telephone: 0483 31261 Telex: 859556 SCITEC G

252 DISPLAYS. OCTOBER 1984