Question on TTL flash


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ardnirun

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Sep 22, 2008
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#1
I was wondering..knowing that the system would measure the distance and what not for the correct flash strength..will it know whether the flash head is pointing upwards(bounce flash) or towards the subject or to the back of the photographer..is its calculation based on flash head pointing forwards?

correct me if i am wrong
 

Rashkae

Senior Member
Nov 28, 2005
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#2
I was wondering..knowing that the system would measure the distance and what not for the correct flash strength..will it know whether the flash head is pointing upwards(bounce flash) or towards the subject or to the back of the photographer..is its calculation based on flash head pointing forwards?

correct me if i am wrong
Please try to research this online: "TTL vs ADI flash". What you are thinking of is ADI flash. TTL means "through the lens", in other words, it measures the light coming through the lens and adjusts flash power accordingly.
 

ardnirun

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Sep 22, 2008
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#3
Please try to research this online: "TTL vs ADI flash". What you are thinking of is ADI flash. TTL means "through the lens", in other words, it measures the light coming through the lens and adjusts flash power accordingly.
ahh..my bad..i shall rephrase..
does shooting with flash (in whatever context..ttl or adi flash) always measure correct exposure assuming that the flash head is pointed towards the subject?does the direction of the flash head affect this?
 

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Rashkae

Senior Member
Nov 28, 2005
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#4
ahh..my bad..i shall rephrase..
does shooting with flash (in whatever context..ttl or adi flash) always measure correct exposure assuming that the flash head is pointed towards the subject?does the direction of the flash head affect this?
Depends on the flash and the camera, really. In most cases, my camera gets it right (even with the flash pointed in a bounce position); sometimes not, which is when I need to manually override flash power.
 

catchlights

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Sep 27, 2004
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#5
physically, light diminished as distance lengthen.

and if you aim the flash head at an area, the light bounce back and light on your subject, you will lose two to three stops exposure compare aiming direct at your subject.

when shooting TTL in bounce light situation, the flash will output more light to compensate for the correct exposure.
 

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May 24, 2008
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#6
I am not very sure about this. I read from somewhere that the flash will fire some pre-flashes, then the camera will calculate the correct flash value, then it feeds the proper value to your flash. So, no matter what direction your flash head is pointing it will give you more or less the same exposure of the subject. Although your flash might work harder if you point it on other directions rather than direct.

Please do correct me if I am wrong. :cool:
 

calebk

Senior Member
Jul 25, 2006
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Clementi
#7
TTL will more or less give you as close to what it deems is correct flash exposure, regardless of whether you are pointing the flash head forward, upwards, sideways or backwards. It will try its best, but it is not 100% foolproof.
 

J-Chan

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Sep 21, 2005
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#8
this is of course within the limits of the flash's GN, don't expect a proper flash exposure if what you're bouncing off is too far away and the flash is at its maximum output..
 

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