what is I-TTL
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Yes yes, anyone can advise on what is it? and what is E-TTL, or TTL or anythingl ike that? Which is the one Canon EOS is using? (specifically for me, my 300D). Cos my flash seems to overexpose everytime.
TTL - With film SLR cameras, light passed through the lens and reflected by the film is continually measured by the flash sensor during exposure until the correct exposure has been achieved. This system is referred to as a TTL flash metering system (see the image of a TTL flash sensor system below).
D-TTL - Digital camera sensors do not reflect enough light for the TTL sensor to use during exposure so metering is performed using light from the *Monitor pre-flash reflected from the shutter curtain before the exposure, the end of the exposure is detected by the camera metering system. This system is referred to as a D-TTL flash metering system.
*What is ''Monitor pre-flash' (or 'pre-flash')?
The Speedlight fires a series of pre-flashes to 'test' the scene, using the flash meter it can then calculate exposure just before firing the main flash to illuminate the subject during the actual exposure time. The pre-flashes are lower power than the main flash. Nikon use the term DX as a suffix for Speedlight names that support the pre-flash function which is an essential element of D-TTL operation.
i-TTL - Is an evolution of D-TTL that incorporates more accurate systems for pre-flash. Metering is performed using light from the pre-flash reflected from the shutter curtain before exposure as with D-TTL. However the pre-flash fired is much stronger and of much shorter duration than D-TTL to achieve greater accuracy using the flash sensor.
i-TTL Speedlights are compatible with Nikon's Creative Lighting System (CLS) when used with compatible Digital SLR cameras (D2H and D70) offering new functionality that is not compatible with non i-TTL Speedlights.
D-TTL - Digital camera sensors do not reflect enough light for the TTL sensor to use during exposure so metering is performed using light from the *Monitor pre-flash reflected from the shutter curtain before the exposure, the end of the exposure is detected by the camera metering system. This system is referred to as a D-TTL flash metering system.
*What is ''Monitor pre-flash' (or 'pre-flash')?
The Speedlight fires a series of pre-flashes to 'test' the scene, using the flash meter it can then calculate exposure just before firing the main flash to illuminate the subject during the actual exposure time. The pre-flashes are lower power than the main flash. Nikon use the term DX as a suffix for Speedlight names that support the pre-flash function which is an essential element of D-TTL operation.
i-TTL - Is an evolution of D-TTL that incorporates more accurate systems for pre-flash. Metering is performed using light from the pre-flash reflected from the shutter curtain before exposure as with D-TTL. However the pre-flash fired is much stronger and of much shorter duration than D-TTL to achieve greater accuracy using the flash sensor.
i-TTL Speedlights are compatible with Nikon's Creative Lighting System (CLS) when used with compatible Digital SLR cameras (D2H and D70) offering new functionality that is not compatible with non i-TTL Speedlights.
Hi i realize that the flash sometime does the compenstion of the ev+- by itself . How to have better control of the flash . For example i purposely control the ev of the flash by -1 at very dark place but the flash automatic compensate it by + 1.why does it to that. 
I using IttL for most of my shot .
Do we really need to do the compensation ourself or can leave it to the flash.
is it like that way that we compensate when we using the camera?
Thanks
I using IttL for most of my shot .Do we really need to do the compensation ourself or can leave it to the flash.
is it like that way that we compensate when we using the camera?
Thanks
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