Modern Classic SLR Series :
Canon EOS-1N Series AF SLR camera
Focusing with EOS-1N - Part III

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Manual Focusing Use manual focusing when the subject is difficult to focus with the camera’s autofocus system, or when you need to control the focus for alternative focus effects.

EF_AFMF_switch.jpg AFMF_switch.gif
Operation:- 1 Set the lens’ focus mode switch to “M”. The AF mode display is extinguished in the LCD panel. 2. While pressing the shutter button halfway and looking through the viewfinder, turn the lens’ manual focusing ring until the subject appears sharp. When the focus mode is switched from “AF” to “M”, the focusing point and in-focus indicator in the viewfinder light when the subject is in focus.

Full-time manual focusing with Canon's USM (Ultrasonic Motor) EF lenses

(This method of focus adjustment cannot be used if your USM lens does not have a distance scale). Autofocusing can be overridden by manual focusing at all times. Most USM lenses have a full-time, manual~focusing feature allowing you to subtly adjust the focus with the focusing ring after autofocusing is achieved in the One-Shot AF mode. You can, therefore, focus manually even in an AF mode, which is one of the major features of the EOS system. Lastly, when using a USM lens equipped with an electronic manual focusing system, setting this custom function will allow manual focusing only when the lens’ focus mode switch is set to “M”.To disable AF altogether and switch to manual focus, proceed as follows:

Sparks_Lane_in_Cades...by Mike Niemi (43k)  Loading ...
<<<-- Some scene whihc has little outlines for the camera AF system to detect may require MANUAL Focusing.

Sparks Lane in Cades ..

Credit: Image courtesy of Mr. Mike Niemi®, US. Mike Portfolio can be accessed via Pbase Link . Image copyright © 2006. All rights reserved. Please respect the visual property of the contributing photographer.

A typical Canon USM lens explained
Operation:- 1. Switch the focus mode on the lens to "M"; then, 2. Focus using the lens focusing ring. Focus is achieved when the subject looks sharp. If you press the shutter button halfway and turn the focusing ring, the active focusing point flashes red and the in-focus indicator lights when focus is achieved.

1: Even in an AF mode, full-time manual focusing lets you focus manually without switching the focus mode.
2: Even when focused manually, the focusing point in the viewfinder flashes red.
3: For exclusive manual focus, set the focus mode switch on the lens to W."

Part TWO A) Technical Description of Canon EOS-1N AF System

The Canon EOS-1n camera features a high-performance AF system optimized to operate quickly and accurately according to the photographer's will. The EOS-1N provides not only the three AF system features common to all EOS cameras i.e. (a) fast focusing speed, (b) strong performance in low light, and (c) high focusing precision - but also other advanced features such as (d) wide-zone focusing using a high-precision Multi-Sensor BASIS ( || +|| ) and (e) real-time focusing point selection via the quick control dial.

Wall paper.. Shanghai 2006

Wall painting with pedestrian... Shanghai, China 2006. Private Visual works for another project on www.IMAGES.com.my

(1) AF Optical System Basic Configuration

Canon EOS-1N AF suystem illustration   Multi-BASIS chip for Autofocusing with Canon EOS-1N

BASIS AF chip , Canon 650   Compared the above sophistication of multi-BASIS chip with the early BASIS chip used in the first generation Canon EOS-650.

The optical system used for rangefinding is basically the same as the system used in the EOS 5 except that the central C-V-BASIS vertical line sensor is designed for use with lenses having a maximum aperture of approximately f/2.8 or brighter (same as the EOS-1's V-BASIS design). All other light beams used for focusing only require use of a maximum aperture of approximately f/5.6 or brighter (same as other EOS cameras).

(2) Focusing Principle The focusing principle is the same type of TTL-SIR (stands for Through The Lens Secondary Imaged Registration) system used in previous EOS SLRs. However, the EOS-1N's system combines the high-precision AF design of the previous Canon EOS-1 (with the C-V-BASIS central vertical line sensor providing three times the image shift sensitivity of the other sensors) with the multi-AF design (wide-zone focusing/five focusing points) of the eye-controlled Canon EOS 5, realizing high-precision multi-AF.

(3) Actual Optical System As shown in the illustration
A, the light passing through the shooting lens passes through the full-surface half-mirror (37% transmission ratio), is reflected 83 degrees downward by a sub-mirror (total reflection), passes through a field lens, is reflected again at a slight upward angle by another mirror, and passes through an infrared cutoff filter, fixed diaphragm and secondary image formation lens (see illustration) to where it finally impinges on the multi-BASIS focusing sensor.

Technical drawing on how Canon AF system works A

Construction of rangefinder unit inside the Canon AF module

The rangefinding unit is constructed as shown at the last illustration, and the positional relationships between the actual focusing points and the AF -frames in the viewfinder are shown in another technical illustration B.

Secondary Image The secondary image formation lens consists of two sets of lenses, one each for horizontal focusing points and the vertical focusing points. Four parallax images are formed on the sensor. From these images, the distance is detected.

(4) High-Precision Multi-Sensor BASIS The high-precision Multi-Sensor BASIS focusing sensor used in the EOS-1N adds the following improvements to the cross-type BASIS used in the older model, Canon EOS-1, this enabling independent focusing at five different points in addition to high-precision AF operation.

(i)   The cross-type line sensor (featuring high-precision horizontal line detection and vertical line detection) used for focusing in the center of the frame and the four line sensors (detecting horizontal line components) to the left and right (two on each side) of the central sensor are all fabricated on a single chip as a multiple line sensor.
(ii)   In addition to the ainplifier provided for each pixel, an amplifier circuit with a gain factor of 20 is incorporated on-chip to improve the sensor's sensitivity and S/N ratio (signal-to noise ratio).
(iii)   A built-in control circuit similar to the one used in the EOS 5 enables the camera to focus even ultra-low-contrast (90:80) subjects.
(iv)   A redesign of the circuit layout and use of finer signal pins (reducing the pin pitch from the EOS 5's 0.8 mm to 0.65 mm) allows the AF sensor to be combined with the fine-spot metering AE sensor in the same size package as the EOS 5, resulting in a concentration of functionality and a more compact design.
(v)   An anti-reflection film like that used in the EOS-1 is fabricated around the light reception area, preventing reflections from the chip's aluminum surface and stabilizing the detection signals.
(vi)   An interface circuit is built into the BASIS drive signal input section to prevent the BASIS drive signal from influencing the AE sensor unit, improving the AE sensor's signal-to-noise ratio.
BASIS chip in relation to Viewfinder AF selection BASIS chip technical function illustration asis_illus.gif
The number of bits and dimensions of each pixel in the Multi-Sensor BASIS are shown below:-
Total number of bits Dimensions of each pixel Effective light reception area
  total No. of bits dimension of each pixel effective light reception area
Center H-BASIS 42 x 2 23us-icon x 120us-icon 0.97mm x 120us-icon x 2
V-BASIS 29 x 2 23us-icon x 120us-icon 0.67mm x 120us-icon x 2
Left & Right V-BASIS 30 x 2 23us-icon x 120us-icon 0.69mm x 120us-icon x 2

(5) Focusing Point Selection Method :- As explained in the custom function chart, manual focusing point selection is generally carried out by pressing the focusing point selection button while turning the main dial, but CF-No. 11-2 can be used to change the operation so that the focusing point can be selected in real-time via independent operation of the quick control dial. This operation is possible while SW- I is. on, the metering timer is on, or during continuous shooting. AF -and AE setting~are recalculated each time the -focusing point is changed, enabling real-time AF and AE measurements while changing the focusing point. During this operation the focusing point selection sequence stops when the far left or right point is reached, preventing accidental setting of the automatic focusing selection mode.

Underwater at Aquatic, Kuala Lumpur Convention Centre, Loading ......
The Aquatic, Kuala Lumpur Convention Centre. Another typical scene to use AF control. In such case, MANUAL FOCUSING works better.

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Credit: Image courtesy of another good friend, Mr. Vincent Thian® Photo Editor of AP (Associated Press, regional bureau/Malaysia).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

(6) Rangefinding Calculation and Increased AF Speed

a) Data calculation In automatic focusing point selection mode, operation is the same as the EOS 5 with calculations carried out simultaneously for the H-BASIS and five V-BASIS focusing sensors. The calculation order is determined by how fast each point performs its signal detection process, thus minimizing calculation time. In one-shot AF mode, the focusing point measuring the. shortest distance to the camera is i generally chosen as the reference focusing point; however, this point is not used if the reliability of the point is very low (such as with a low-contrast subject) or if the point is extremely close to the camera (closer than the lens' closest focusing distance).

b) Increased AF speed The EOS-1N incorporates a high-speed super-microcomputer with a reference clock frequency of 12MHz dedicated to performing AF calculations, enabling the camera to focus as fast as or faster than the EOS-1 despite the use of five focusing points. Actual AF focusing speed data is shown in the chart here (
Click for an enlarged view).

(7) Focus Prediction Control The EOS-1N's focus prediction control function is carried out in basically the same manner as the EOS-1, with minor differences depending on whether the EOS-1N is used alone or combined with the Power Drive Booster E1 In automatic focusing point selection mode, as with the EOS 5, priority is given to the center, so it is necessary to cover the main subject with the central. focusing point at the start of focusing. However, since the side focusing points are constantly in focus-ready mode (accumulating data), Al Servo AF will hold focus on the subject even if the subject moves away from the center sensor to one of the side sensors.

Canon EOS-1N and EOS-1 AF CPU compared
Model Reference clock frequency Minimum calculation time
Canon EOS-1 12MHz 0.33us.symbol
Canon EOS-1N 12MHz 0.17us.symbol

For an example:- The focus prediction capability of EOS-1n when using a telephoto EF 300mm f/2.8L enables the camera to continuously track a subject moving directly towards camera at a speed of 40km/h to a shooting distance of 7m.

| Previous | NEXT | Sophisticated Metering Systems deployed in the Canon EOS-1N

Focusing (Autofocus/ Manual Focusing): Part I | 2 | 3

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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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Volunteered Maintainer(s) for the Canon EOS-1N Series Message Board: Philip Chong, Editor, Digital Camera Magazine; Vincent Thian, Photo Editor, Malaysian Bureau, Associated Press "AP", CYleow, Ex-photo Editor of local daily, The Star; Gary Rowan Higgins, Australia and other nice folks on the web.

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