Classic SLR Series :
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Exposure Control System Virtually every modern SLR camera is deployed with a few metering systems to aid photographer for exposure guide. In many ways, this has progressed to a stage where most photographers would rather depend on the metering system in the camera to resolve even the most complex lighting situations faced than configuring on their own in exposure calculation. The main issue is responsiveness and in actual fact, metering technologies have been kept on improving a;; the time. The current trend is multi-zones evaluative system, which has been made like a standard feature now on majority of SLRs. Usually, it is supplemented by a host of conventional metering systems such as the classic center-weighted, spot or partial metering. One way or another, metering is a key element for precise exposure control and that is why I would discuss this ahead of the other
A portrait of the retired, ever-outspoken Tun Dr. Mahathir, ex-political premier of Malaysia - once was hailed as Asia's most influential political figure was captured through the lens during a World Meets on Human Rights Issue. Depending on usage and preference, many people may categorize a camera mostly for leisure photography. But for those who are at work, a dependable professional class SLR camera is a working tool. To an all rounder photographer, he may have to use it for news, reportage, journalism, sports, advertising and even for a little leisure photography on or after work. The serious amateurs, who may also use it as a yardstick to measure ruggedness, dependability and most often, the affordable who also appreciates its true value would settle one for personal use.
Credit: Image courtesy of another good friend, Mr. Vincent Thian® Photo Editor of AP (Associated Press, regional bureau/Malaysia) on frequent assignment to cover other political events in Asia. Vincent also maintains an AsianphotoGS.org. Selective of his older works can also be found at a section of Windows in MIR site or at his Portfolio in MIR Image copyright © 1996-2005. All rights reserved. Please respect the visual property of the contributing photographer.
a) Metering Optical System and AE sensors. The construction of the metering optical system is shown As shown at the table below:-
Metering Systems and AE Sensor Positions
Metering Systems AE Sensor Position 1. Evaluative metering Above the eyepiece lens 2. Partial metering 3. Spot metering (CF) 4. Center-weighted average metering (CF) 5. Fine spot metering Bottom of mirror box, on BASIS light receptor chip surface 6. TTL off-the-film reflection metering Bottom section of mirror box
To select or switch to another metering system. While pressing the metering mode selector, turn the Main Dial to select one of five modes. The selected metering mode is shown with a corresponding icon displays on the top LCD display as well as a similar symbol inside the viewfinder. When the desired metering mode is displayed on the LCD, release the metering mode selector to register the selection.
The three primary metering systems will rotate when Main Dial turns in either direction.
Metering system optics As with the EOS-1, three AE metering sensors in different locations are used for the six metering modes. The 16-zone metering sensor above the eyepiece is used for 16-zone Evaluative, Partial, Spot, and Center-weighted Average Metering. At the bottom of the mirror box, a metering sensor employing Multi-BASIS is used for Fine Spot Metering. Also at the bottom of the mirror box, the three-zone TTL flash exposure metering sensor is used for off-the-film ("OTC") metering. The EOS-1N has six metering modes including off-the-film flash metering. The metering mode can be selected (Five metering modes easily switchable) to suit the user's objectives.
Illustration of the SIX (6) types of metering are built into the Canon EOS-1N. Like the previous EOS-1 models, the AE (Auto Exposure) sensors used for the various metering functions are dispersed in three (3) locations
i) 16-zone metering sensor: For optimum exposure control, metering info from the 16 zone metering sensor is coupled with the focusing points. This sensor unit which provides the evaluative metering system uses the same sensor chip as the eye-controlled focus Canon EOS 5, providing evaluative metering and spot metering (linked to the five focusing points - enabled by Custom Function). Metering areas A0-A4 correspond to the AF system's five focusing points, enabling evaluative metering to be performed.
The key highlight of the Canon developed, if not original Evaluative metering, which is able to detect subject's size and executes automatic exposure compensation. one way of another, photographers may sometimes, encounter difficulty in determining exposure as light meter reads reflected light in straight forward manner. So, in some tricky situations, exposure compensation is therefore necessary. But executing correct "amount" of of compensation requires a great deal of adequate experience and knowledge to achieve optimum results. Further, frequent adjustments slows down fast picture-taking. The multi-zone evaluative metering system, divides the viewfinder scene into a number of metering segments which determine the exposure and computes all the available data collectively which includes evaluation of subject reflectance as well as the surrounding scenes where exposure compensation is set automatically so that the subject is properly exposed. The system works even in backlit situations. So, this process is handled automatically by the camera and free photographer on the subject matter.
<<<---Sunset and Landscape photography by Roberto Carli, Italy.
Credit: Image courtesy of Mr. Roberto Carli® from Siena, Toscana, Italy. His Portfolio is under construction but should be up soon. (alternate alternate Portfolio at Usefilm) Image copyright © 1996-2005. All rights reserved. Please respect the visual property of the contributing photographer.
a) Evaluative metering Sensor zones Divisions and their output characteristics The EOS-1N's evaluative metering system has 16 zones within the scene's metering area. It can estimate the subject's size and surrounding conditions and set the proper exposure accordingly The diagram shows the out put characteristics of the zones. Evaluative Metering assumes that the in-focus object is the main subject. When Evaluative Metering and the One-Shot AF mode are set, the auto exposure is locked (AE lock) at the same time focusing is achieved.
Intermediate Metering Area Main Subject Metering Area Peripheral Metering Area
This is possible because the five focusing points are linked to the 16-zone evaluative metering system. Accurate evaluative metering is therefore attained regardless of which focusing point achieves focus. In the case of manual focus, evaluative metering is linked only to the center focusing point.
The 16-zone evaluative metering pattern and focusing point linkage. The five focusing points which handle independently for each focusing point are in zones A0 to A4 respectively. Actual metering is carried out as shown, the light metered in the subject zones, intermediate zones, and peripheral zones is compared, and exposure compensation is set in 1/4 stops (in 0.25-stop increments) added when necessary.
Note:- In manual focusing mode, evaluative metering is carried out using the central metering sensor A0, regardless of whether the focusing point selection mode is set to automatic or manual.
<<<--- Reconstruction pattern from original scanned image.
Unlike evaluative metering, the 9-percent Partial Metering area at the center of the viewfinder makes it easy to see where the camera is metering. Moreover, since the metering area is not as small as the spot metering area, the desired portion of the scene can be metered and the auto exposure locked. The usage of the popular, classic Center-weighted Average Metering system in the Canon EOS-1N can be activated when Custom Function CF-8 is set to 1.
<<<--- TRUE colors, stage without flash, ambient light metering at work..
The 16-Zone Metering Sensor for Evaluative metering is also used for handling Partial, Center-weighted as well as AF-point-linked fine spot metering systems.
Credit: Image courtesy of another good friend, Mr. Philip Chong®Ex-Photo Editor of Advance Images Magazine. This image was also being used as entry photo for his Portfolio. Image copyright © 1996-2005. All rights reserved. Please respect the visual property of the contributing photographer.
| Next | The Partial Metering, Spot Metering, Center-Weighted Average meter and A-TTL flash Metering systems.
Metering: Part One | Part Two
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Background and Various Issues | The Basic Features & various Setup
Manual & Auto Focusing | Metering Systems | Exposure Control | Viewfinder Optical
System Flash Photography (with Speedlite 540EZ extension & Selective info on Canon TTL Flash Models:-160E | 200E | 300EZ | 300TL | 420EZ | 430 EZ | 480EG | Macrolite | Other non-TTL Canon flash model
Reliability Issues:- Body Chassis | Shutter Unit | Electronic Circuitry | Film Transport & film handling Secondary Functions:- Custom Function Part One | Part Two | System Accessories:- Film Back Options - instruction for Command Back E1 | Macro/Close Up Part one | Part two and Part III Flash for Macro-Photography | Power Sources -BP-E1 | PDB-E1 | Focusing Screens | Remote Control with Wireless Remote Set LC-3 | System compatibility
Variants of Canon EOS-1N:- Canon EOS-1N RS | Canon/Kodak Digital DCS-1, 3 -5 & 520/560 Series | Full Technical Specification | Main Reference Map / Nomenclature | Resource Centre:- Comparative Charts between EOS-1 & EOS-1N / or with its active Competition(s) (Nikon); Quick Operational Reference Card (278k Gif File); Listings of 7-segment digital numbers/letters appeared on LCD display panel/viewfinders (HTML page); External Link:-Instruction Manual (3.3MB PDF file applicable for both Canon EOS-1N (RS). | Using EOS system for your photography | Bots & Nuts of EOS System - by Philip Chong |
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