Olympus OM-4 User Guide
Contents
1. judgment function which corrects the flash exposure in either direc tion based on a single manual setting and fires the flash only when it s needed to obtain the correct exposure In addition to the above the OM 4 incorporates many subordinate functions including self timer battery check view finder display cutoff finder illumination cutoff etc These numerous and complex functions are electronically interrelated and user selected __ All the OM 4 s multiple functions are organized in a manner similar to the sys tems of large scale computers Essential ly the camera s computer system consists of the following four packages 1 The CPU central processing unit of the microcomputer which is the nucleus of the system 2 The light measuring sen sor consisting of the SPD silicon photo diode and amplifier 3 Large scale bi polar IC which contains an analog to dig ital A D converter 4 The LCD driver IC which controls the camera s viewfind er display The OM 4 s computer system Perhaps the easiest way to explain the operations of the OM 4 s on board com puter system is to compare its functions to those found on a typical big computer To begin with the OM 4 provides in put units that are analogous to a large computer s input keyboard These are The shutter release button auto manual switching lever spot metering button memory all clear lever2. human engineering and after considering their frequency of use The aim was to have them be easily located by feel and operable at the touch _ of a fingertip with the camera at eye level Of particular importance was the front right hand placement and design of the memory ali clear lever which holds or cancels all spot readings if the photogra pher changes his mind The OM 4 s electronic circuitry Functionally the most important and distinctive of the OM 4 s internal systems is its on board microcomputer and associ ated mechanisms Of course integrated circuits ICs have been at the core of camera electronics for over a decade including the Olympus OM 2 of 1975 In contrast to the OM 2 s electronics the OM 4 s circuitry provides multiple programs to control various new func tions In addition to TTL direct light mea suring as in the OM 2 these include spot metering multi spot metering an AE lock which instantly memorizes light measurement values a calculator func tion which executes the optimum expo sure based on values stored in the memo ry and finally highlight and shadow functions which calculate and execute exposure based on the photographer s preferences in overall tonal rendition Moreover automatically read exposure values are memorized and may be recalled by the memory function for up to 60 min In autoflash mode the OM 4 provides an automatic
3. 4 Shadow button 6 Mode selector lever 5 Accessory 11 Shutter release button shoe 7 Rewind crank l 3 Spot metering button 8 Film speed dial Exposure 2 Rewind release l compensation dial button 1 Film advance lever 9 TTL auto cord socket 10 Viewfinder light window 14 Hi light button j 7 2 13 Memory signa 20 Mode selector knob y 12 Clear Memory iever KD 21 Film speed knob w ZEER 15 Rewind release switch ZA 22 Film speed Exposure compensation base 16 Shutter release shalt 6 23 Exposure compensation kneb 17 Film advance shaft 24 Shutter first curtain tension drum 2 A 18 Flim counter 25 Shutter second curtain tension drum 19 Finder indicator thread 26 Shutter first curtain contro magnet ae AE 27 Shutter speed integral base 32 Grip lock screw a5 DS h a SNES eS Shutter dial connective gear mE 7 Z 4 29 Shutter second curtain control magnet 30 Shutter first curtain drum 31 Shutter second curtain drum 33 Camera grip 39 Camera back switch DRE 38 Tripod socket 40 Rewind crankshaft hole 34 Shutter release piate 41 Motor coupling terminal 42 Mirror charge connective lever 35 Motor guide pin hole 43 Shutter charge gear 36 Film check switch l 44 Motor coupling socket 37 Battery chamber 46 Motor cover Disassembly and Drawings by Tetsuo Koyama 78 Was the
4. 35mm SER already so well A decade ago Olympus introduced the ed into a single exposure Suppose for developed that only minor improve OM 1 first of a generation of extremely example that you see areas of sharply dif _ ments to its basic design were possi compact full featured 35mm SLRs ferent bri ghtness within the frame After ble Olympus thought not and pro Three years later it brought forth the you select the precise areas you want tobe ceeded after more than seven years of equally compact OM 2 the first SLR to included in determining the exposure and e toil and high tech ingenuity to giveus the OM 4 the first SLR to combine incorporate direct through lens metering take separate readings of each an on i i FiA i og i T di s exquisitely precise multiple spot me x ie x ana and dii atomair incacsu tain and TTL autoflash Finally late in them into the exposure yow il get when premely compact OM sized body 1983 Olympus announced the OM 4 the you press the shutter release For eon Here as told to us by two of the OM 4 8s first SLR to combine all the salient fea instance you might choose to take two principal desig ners is how and why off the film and or patterned shutter cur board computer calculates and integrates _tures of a sophisticated professional expo _ separate reading
5. D Converter Voltage Judgment Circuit Electronic Flash Con trol Circuit Shutter Speed Integral Circuit Self Timer LED vena ao Light LED Drive Circuit LCD Display In order that the LCD display be as leg ible as possible without causing eye strain the designers chose the so called negative display method light fig ures against a darker background l The LCD display 7 The OM 4 s exposure information dis play panel is situated below the viewfind er screen In automatic exposure mode numerals from 1 to 2000 are arrayed hor izontally and the camera selected shutter speed is indicated by a dotted bar This bar extends and contracts in response to the lighting conditions and its tip indi cates the shutter speed the camera will provide when the shutter release is pressed The individual unit dots compris ing this line indicate the exposure in EV increments providing approximately the same precision and single glance read ability as an analog readout system When Continued on page 142 _ MODERN PHOTOGRAPHY Continued from page 138 as the user selects the spot metering mode a diamond shaped dot appears above the bar to mark each individual spot metering value up to a total of eight separate read ings Viewing these dots shows at a glance the distribution of exposure read ings so the photographer can easily grasp the range of exposu
6. viewfinder illu mination button self timer lever shutter speed ring and flash control terminal Operating instructions from these input units are transmitted to the CPU The processing unit monitors the input instructions by means of time sharing in order to respond as efficiently as possible to any series of input instructions The most important functional element of the OM 4 the light measuring sensor controls both spot and averaging light measuring Switching in this two mode system is controlled by the spot metering button which tells the CPU to switch over to spot metering mode First the sen sor reads the light as an analog value which is then converted into a digital val ue by the A D converter The exposure value is then stored in the multi spot AE Lock RAM random access memory in the microcomputer All individual spot exposure readings and any further instructions from the aforementioned in puts are stored and processed in the operation register This processed infor mation is always displayed on the LCDs in the finder In other words the OM 4 s finder displays are equivalent to the CRT cathode ray tube displays of large com puters Thus the photographer can always monitor the processed information con tained in the microcomputer while con tinuing to view and to focus through the camera at eye level Continued on page 138 136 MODE
7. RN PHOTOGRAPHY INSIDE YOUR CAMERA Continued from page 136 This full time monitoring capability is made possible by the time sharing system of the CPU which transmits the results of all calculations immediately to the LCD driver At the same time the CPU outputs the results of these calculations to the shutter speed ICs in order to control the exposure Both AE shutter speeds and _ flash brightness are controlled in a similar manner the end results of any of these processes being a single correct expo sure value a Once an exposure value has been cal culated the CPU determines whether EUPHOTIC SENSOR Spot Metering Light SBC Center Weighted Avg Metering SBCP 7 INPUT UNITS Release Auto Manual MICRO COMPUTER MuliSput AE Lock RAM Spot Highlights wi Operation Register Shadow Mernury Clear Batter hec d Self Timer O F urination LCP Driver Display RAM ev The OM 4 s Electronic Heart The camera s innovative IC system for exposure control diagramed for clarity E flash is required to achieve the proper exposure and prepares itself to accept input information for the next exposure Thus the CPU processes and transfers information among the input units light measuring sensor LCD finder dis play and the exposure control unit an array of functions equivalent to full scale data processing in large computers Packagi
8. ens optical assembly 3 which includes an aspherical element and an infrared cutout filter is located in front of the stationary sensor 4 a Oo Although the basic shutter mechanism of the OM 4 is based on the shutters found in previous OM models over 50 different improvements were made to achieve a sta ble 1 2000 sec shutter speed along with improved overall accuracy Improve ments found in thc OM 4 s accessories include motor driven film rewinding and the ability to attach and remove the motor with film loaded With rare exceptions single lens reflex cameras have stuck with center weighted metering systems for the best part of two decades With the emergence of the OM 4 we now have multiple spot metering sophistication and more precise user con trol of the exposure process THE END MODERN PHOTOGRAPHY
9. gs which are automatically integrat Continued on page 136 ON Dioptric adjustment eyepiece 0 o 66 CMOS 4 bit microcomputer 68 CMOS LCD driver ed gt she RGR 5 N 3 70 Main reflex mi ror i W j en Aperture drive lever T a INSIDE YOUR CAMERA Continued from page 79 Existing motor drives film winders data backs 250 exposure backs and of course all lenses are fully interchange able among all four OM models includ ing the OM 3 This modular systems approach allows photographers to add a wide variety of specialized accessories The pentaprism housing section atop the OM 4 was designed for maximum compactness yet it contains some of the camera s most important and innovative features These include complex electron ic circuits the new all LCD finder read out systems and the adjustable diopter eyepiece Considerable effort and ingenu ity were required to get such an enormous amount of new electronics and precision mechanics into a body as compact as the OM 4 s Indeed this was the major hur dle faced by the OM 4 design team Another difficult engineering problem was devising a multi function spot me tering system that was comprehensive yet easy to use To provide easy access to the OM 4 s unique metering functions a Cluster of buttons adjacent to the shutter release was employed each of whose size shape and position was determined on principles of
10. l eyesight see text for operational details The drawing below left shows the OM 4 s eyepiece adjustment mechanism Pull out knob 1 on the left hand side of the pentaprism housing and the knob is now free to rotate By rotating this diopter adjustment knob while sighting through the finder you can select the position that s optimal for your personal eyesight Here s how it works When you rotate knob 1 screw channel 2 which is connected to knob 1 travels along pin 3 causing lever 4 to turn counter clockwise Pins 5 and 6 affixed to lever 4 now move laterally in their respective channels causing frame 8 holding the front eyepiece lens to move forward with respect to frame 7 which contains the rear eyepiece lens In this manner the optical strength of the com pound eyepiece lens is varied OM 4 s Metering System 20 of light striking main mirror 1 passes through to secondary mirror 2 and is reflected down to Compound Euphotic Sensor 3 and 4 in base of body See text for additional details The drawing above illustrates in detail the metering mechanism The main mir ror 1 is a special semi transparent mirror which is multi layer coated on both sides This special mirror reflects 80 of the incoming light rays up to the viewfinder while the remaining 20 are reflected downwards via a subsidiary mirror 2 to the light measuring sensor A three l
11. ng the system Getting the complex large scale elec tronic system outlined above into the compact body dimensions of the OM 4 proved to be a tough assignment for Olympus Early prototype OM 4s had much larger pentaprism housings than previous OM series models but Olympus deemed this big bodied OM 4 unac ceptable and began the difficult task of packing more features into a smaller space than ever before The ICs were packaged more compactly by using advanced tech 138 Mirror Con m trol Magnet e Orive Circuit blellslsletts ER Memory Exposure RAM nology including stacking the IC pack ages on both sides of an ultrathin flexible circuit Ay Each integrated circuit designed for minimum power consumption is driven at 3 volts at very low amperage Much time was spent in analyzing the OM 4 s diverse electronic systems during the development of the CPU which is con trolled by a CMOS 4 bit 4 byte micro computer The development of the LCD finder display system proved to be espe cially difficult The LCD contains more than 100 different alphanumeric ele ments and each one is tiny some mea suring only 10 microns Also the display had to be legible over the extremely wide tcmpcrature range INPUT UNITS tSO ASA Shutter Speed Aperture Compensation Electronic Flash Mirror Control Magnet Shutter Cori trol Magnet Flash Charge Finish LED V SI BIPOLAR A
12. re values and balance of each scene or subject In the spot read ing mode the bar still indicates the prop er exposure shutter speed but in this case it represents the calculated value of the entire series of spot readings z The sophisticated finder display is one of the major factors enabling OM 4 users to control the camera s multi spot me tering system with ease and confidence But to achieve maximum efficacy from its design Olympus had to improve the view finder eyepiece also _ i The most singular aspect of the OM 4 s finder eyepiece is that it provides a wide range of diopter adjustment for eyesight variances This not only enables more precise viewing and focusing but also allows the photographer to read the com plex finder displays clearly and with instant recognition In designing the eye piece special emphasis was placed on the following capabilities 1 A wide adjust ment range for dioptric correction be tween 1 0 and 3 0 diopters 2 A high viewfinder magnification 3 Mini mizing distortion in the viewfinder image when the photographer fails to center his eye behind the eyepiece when looking through the finder 4 Achieving a com pact design with a comfortable and pleas ing shape gt a The OM 4 s Dioptric Adjustment Eyepiece _ Turning gear 1 causes distance between front and rear eyepiece to change thus varying its focal length to suit individua
13. s of highlight and shadow s _ sure meter plus a comprehensive LCD areas of a face plus a thirdreadingoffthe gt g5 et Ge _ finderreadout system in atraditonal OM subject s clothing ee ne by Y Maitani and K Fsun _sized body oo oo 0e ooon The exterior design of the OM 4 repre gt E oe As the name suggests the OM 4 s sents a logical extensionof the OM 1 and Gi _ 65 Viewfinder illumination 62 oe oe 61 Adjastment Pots eet 5 o 49 Selbtimer Electronic i Ko ARE beeper muffling switch 3 7 P 67 LCD i aR E oe a ed 69 Manual shutter speed ring k Fe Me 1 a a S 60 Viewfinder a lt 48 Compoun G SBC Oeics iHumination button aite ni l A i I AY j E 4 4 A 51 B lock Button ha 56 Self timer Battery check signal 57 Self timer Electronic beeper muffling lever 52 Flash sync socket cover 4p 73 Focusing ring Y 54 Mirror charge lever PAS AA N s gt S evita M K INE 3 3 74 Aperture ring V 50 Auxiliary 75 Preview button reflex mirror measuring di crete limited areas of the control arrangement of the OM 4 is quites n subject either individualiy orin multiple similar to that of the previous models aes Multi Spot Metering system is capable of OM 2 In fact the basic body shane and ee 76 Lens release button 79 readin
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