ETTL stupid question

Started Dec 14, 2012 | Discussions thread
sacentre
Senior MemberPosts: 1,160
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Re: ETTL stupid question
In reply to IndianaSteve, Dec 17, 2012

Hi Steve

I think ETTL is great most of the time but I believe any static situation like in a studio, where diffusers are used, it's best to use manual flash with a LM.

There's also the consideration that ETTL will miscalculate the distance information it gets from the lens when the flash head is in the horizontal position, pointing straight forward AND when any kind of modifier is used. There is a Canon tutorial about this somewhere.  It doesn't matter if the flash is off camera or mounted in the hot-shoe.

Once the flash head is angled off the horizontal or to one side when bouncing off walls or ceiling, then the ETTL will calculate correctly based on the pre-flash and distance info it gets from the lens.

When I first encountered this, I couldn't understand why all my shots were under exposed when I put a small diffuser on. I just assumed that as long as I'm within the power output range of the flash, ETTL will more or less guarantee correct exposure.

I started a thread about it which got plenty of input from people far more knowledgeable than me

http://forums.dpreview.com/forums/post/38415551

It may be of interest.

Trevor

IndianaSteve wrote:

ETTL works by metering the subject and then communicating the correct setting to the camera. So why do people still use ETTL when using a flash in a bounce umbrella or soft box?

The flash's meter isn't pointing at the subject so you won't get a correct reading, right?

I just dont' understand the advantages of using ETTL when the smart flash cannot directly meter the subject.

Someone please clue me in here.

Also, are there any advantages to using ETTL when it is not communicating with the camera?

I have a number of flashes and use them in manual mode (when off camera) with my separate hand help llight meter.

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