Pre-Flash of CANON 580 EXII

[ocy82]

I have a CANON 580 EXII flash. However, I am confuse with the focus helping in low-light condition. With ETTL-II mode, 580 EXII will help focusing by AF-Assist Beam only? Or it will emit a so called "pre-flash"?

I dont see my 580 EXII emit any flash while focusing (only the AF-Assist Beam is working). I remember the on-camera flash will keep emit while in low-light condition.

Please share with me more about this issue.

Thank you.

[turbodude]

AF assist lamp is the red light, pre flash is ettl, you rarely see it unless you have your eyes open and have long shutters speeds

[00silvergt]

As the above poster said, the preflash fires just about the main flash fires. The preflash fires so that it can measure the exposure and ETTL-II would set the flash to make the "correct" exposure.

This usually throws off the optical slave flashes or boosters. A good work around would be to hit the * before taking the picture, wait for your booster to recharge and then click.

[PacAce]

I have a CANON 580 EXII flash. However, I am confuse with the focus helping in low-light condition. With ETTL-II mode, 580 EXII will help focusing by AF-Assist Beam only? Or it will emit a so called "pre-flash"?

I dont see my 580 EXII emit any flash while focusing (only the AF-Assist Beam is working). I remember the on-camera flash will keep emit while in low-light condition.

Please share with me more about this issue.

Thank you.
You are correct in your observation of the built-in flash firing a burst of light (what you referred to as "preflash") for focusing. But that is not how the external flashes work. They don't emit a burst of flash for focusing. Instead, as others have already stated, they use a patterned red beam for low light focusing.

[ocy82]

You are correct in your observation of the built-in flash firing a burst of light (what you referred to as "preflash") for focusing. But that is not how the external flashes work. They don't emit a burst of flash for focusing. Instead, as others have already stated, they use a patterned red beam for low light focusing.

Thanks a lot. So, below is the conclusion

Built-in flash: firing a burst of light("pre-flash") for focusing assist
External flash: AF-assist red beam for focusing assist

Am I right? Thanks for solving my confuse. I tought my flash is broken!!!:p

[PacAce]

Thanks a lot. So, below is the conclusion

Built-in flash: firing a burst of light("pre-flash") for focusing assist
External flash: AF-assist red beam for focusing assist

Am I right? Thanks for solving my confuse. I tought my flash is broken!!!:p

Yup, you got it now. :)