OLYMPUS TECHNOZONE Vol.70 2008-4
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World's Fastest AF
with an 11-point-full Twin Cross AF Sensor System
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---- I heard the most important issue with the E-3 was how to enhance the AF's speed and precision.
Tough opinions from users were behind this, opinions that also implied high expectations towards Olympus. To satisfy these expectations, we constantly took cool-headed decisions on what was expected of us and committed ourselves to making them a reality. What were the issues inherited from the E-1? What was their true essence? After conducting research and exchanging views, we began to discern the specifications for a multi-point AF sensor that would satisfy users' demands.
The next questions were about the AF's range-finding points and their positioning. First, we did a statistical analysis using tens of thousands of photographs as samples to ascertain where the main subject was located on the screen. Then, after interviewing professional photographers, we determined the range-finding points and positionings that were optimal for requirements. We found there were actually 11 points. Once the number of range-finding points was determined, we turned to precision.
The main feature of our latest technology is the adoption of an 11-point-full twin cross sensor for the AF. The use of a full twin cross system overcame the problems with difficult subjects while the adoption of a cross sensor pattern where two horizontal and two vertical lines cross each other in a half-pitch shifted pattern (zig-zag array) enhanced precision and sensitivity. This enabled us to achieve enormous improvements in the AF function compared with earlier models.
When asked about the number of possible distance-measuring data points, we used to answer three. What we've achieved here is not merely a simple increase in the number of points, but a design whereby a real cross at all points allows accurate focusing at all 11 points.
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The 11 distance-measuring data point LCD monitor display
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The rear of the E-3
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This method has boosted the functionality of the E-3's AF enormously. To see just exactly what it could do, I accompanied a professional photographer to confirm its moving body tracking and other functions.
As we received feedback at the location, we made on-the-spot adjustments. After we repeated this procedure several times, the professional photographer was satisfied. He told us it was now an AF he could use professionally.
---- How did you work on the AF from the perspective of the lens?
Since the AF sensor expanded the distance-measuring area to cover multiple data points, we had to ensure that all the interchangeable lenses matched. We also had to re-measure the design and real values for all the lenses for all 11 distance-measuring data points. We spent a lot of time taking photographs with various lenses.
To take lens focus precision to a higher level, we developed our own device called an optical encoder to measure positions more exactly. We also incorporated Supersonic Wave Drive (SWD) motors for use in digital image stabilization functions in the actuator for the lens drive. However, we completely changed the control algorithms used for digital image stabilization. Sub-micron-level tracking capabilities are important for digital image stabilization functions but it is also necessary to adjust them for high-speed drive performance when they are used for AF. We had a hard time stopping the lens with high precision while maintaining high speeds under various shooting conditions (such as temperature, postural differences, etc.)
---- Will you use it in all your lenses in the future?
We will probably incorporate the best of everything we developed including SWD with actuators according to the lens characteristics.
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