I guess the only logical way to calculate the distance by using the light
will be to measure the time it needs to travel from one point to another.
Now the range of the subject distance from camera will be from 0.5 m to 54 m
(in case of 540ez) which translates to 1 m to 108 m in terms of the distance
the light travels. Light speed is 300.000 km/s (?), the sensor inside the
flash must be very fast. Does Canon use some sort of atomic clock ?
-----Original Message-----
From: Dave Herzstein [mailto:[EMAIL PROTECTED]]
Sent: 25 Januari 2001 21:48
To: [EMAIL PROTECTED]
Subject: RE: EOS A-TTL and E-TTL
I wonder:
If the A-TTL sensor reads from the surface of the film, how could it read
the pre flash? Moreover, how come the pre flash is fired only when the flash
is directed towards the subject to calculate the distance, when this
information can be fed by the lens (sort of Nikon's D-TTL)?
=======================
The A-TTL pre-flash is read by the flash sensor. Many have speculated that
Canon does not use lens distance information because of patent
considerations.
--
Dave Herzstein
[EMAIL PROTECTED]
http://www.kjsl.com/~dave
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