Talk:Autofocus

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[edit] IRLEDs

I presume that the cameras (still and camcorders etc) which use infra-red light to autofocus must have an IR LED to provide the illumination? I ask because I am trying to estimate the market for such components. Given the number of DSCs and camcorders sold this must be a substantial market for IR LEDs.

Meanwhile, other types of LEDs are being used. For example:

Avago Technologies has introduced a high-brightness green auto focus auxiliary flash light emitting diode (LED) to assist the auto focusing function in digital still cameras when used in low ambient light conditions. The ASMT-FG10 flash LED offers a small footprint, measuring 4.8 x 4.8 x 5.33 mm.

Touted as a low-cost alternative to conventional infrared (IR) auxiliary auto focus solutions, the ASMT-FG10 compact green LED lamp is said to provide the highest brightness and smallest package in the industry. The narrow angle SMT lamp package is suitable for digital cameras that require long distance illumination and a narrow beam pattern. Digital still cameras have twice the sensitivity when responding to the color green than other colors, due to the availability of more photo diodes allocated for green in each pixel, said the company.

The ASMT-FG10 green (530nm) Indium Gallium Nitride (InGaN) dome LED lamp uses an un-tinted, non-diffused lens to provide high luminous intensity within a narrow radiation pattern. It incorporates an encapsulated LED chip on an axial leadframe to form a molded epoxy lamp package with six bended leads for surface mounting. The InGaN material has a very high luminous efficiency and is capable of producing high light output over a wide range of drive currents, said the company.

The easy to install ASMT-FG10 also simplifies the assembly process, which is said to result in a cost savings and better overall performance of the camera. It also features a six-degree viewing angle and is compatible with 2x solder reflow process. It meets IEC/EN 60825-1 Eye Safety Class 1 requirement. The device is RoHS compliant. Click the link for more information about the ASMT-FG10 LED.

The ASMT-FG10 SMT LEDs are priced at $0.60 in quantities of 10,000. They are supplied in 16-mm tape on 380-mm (15-inch) diameter reels for compatibility with automated manufacturing. Samples and production quantities are available now.

Avago Technologies, 1-800-235-0312, www.avagotech.com/led

Earlier this US company had released another type of visible LED: AlInGaP-based orange 612nm LED specifically designed to provide the illumination required to operate the automatic focus function of a digital still camera under low-light conditions. Most cameras use an infrared LED for this function, although some already use visible devices. http://www.ledsmagazine.com/news/2/11/13

RadioShack has a high power IR LED which it says is suitable for AF: http://www.radioshack.com/sm-high-output-infrared-led--pi-2062565.html

A high-performance infrared emitter whose peak wavelength is 940nm. These high-output infrared LEDs are a perfect light source for various kinds of security systems that need higher radiation. They also can be used in products ranging from TV remotes and auto-focus cameras to electronic gates.


81.86.144.210 11:34, 14 June 2007 (UTC)

[edit] Number of Canon EOS 3 AF sensors

Canon EOS 3 has 45 AF points. 6 of them act as high precision cross-type AF sensor with f/2.8 or faster lens. Central point acts as high precision cross-type AF sensor with f/4 or faster lens.

Reference : http://www.bobatkins.com/photography/eosfaq/eos3af.html

I think that this means that Canon EOS 3 has

  • 45 normal precision horizontal-line sensitive single-axis AF sensors (each AF sensor has 2 CMOS sensors)
  • 7 high precision vertical-line sensitive single-axis AF sensors (each AF sensor has 2 CMOS sensors)

So, strictly speaking, we should say that "Canon EOS 3 has as many as 45 AF points" or "Canon EOS 3 has as many as 52 single-axis AF sensors".

What do you think? --shotgunlee 04:52, 9 December 2005 (UTC)


I think it has 45 Area-SIR points in total, arranged as follows:
  • 38 are horizontal-only standard-precision sensors active for any lens faster than f/5.6
  • 6 points come in cross-type configuration with additional vertical high-precision sensors active for f/2.8 lenses or faster, among the horizontal standard-presicion sensors
  • the central point has a standard-precision horizontal sensor for lenses up to f/8, and features a higher-precision vertical sensor active for f/4 lenses or faster
However, it's only my guess and there could be additional horizontal high-precision CMOS sensors; it certainly does not indicate how many actual sensing devices each point employs. --Dmitry (talk •contibs ) 16:30, 31 August 2006 (UTC)