where is external flash EXIF data

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mike nelson - 20 Aug 2006 18:57 GMT

In looking at the exif data for my canon 20d used with canon 430ex flash (as
displayed in photoshop CS), I do not see flash exposure compensation. I
tried turning the flash down 1 stop, once on the flash itself, and
separately via the camera, and do not see anything in the exif data that
tells that I dialed in flash exposure compensation.

Does anyone know either whether or not this data is displayed in the first
place, or whether it is displayed, but perhaps with a non-obvious name?

thanks

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mike nelson - 20 Aug 2006 19:14 GMT

ahh, discovered that the problem is that photoshop does not display this
data. ACD, however, does display it...Curious. Then again ACD does not
display the lens type, whereas photoshop does...

> In looking at the exif data for my canon 20d used with canon 430ex flash
> (as displayed in photoshop CS), I do not see flash exposure compensation.
[quoted text clipped - 6 lines]
>
> thanks

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Paul Mitchum - 20 Aug 2006 22:19 GMT

> ahh, discovered that the problem is that photoshop does not display this
> data. ACD, however, does display it...Curious. Then again ACD does not
[quoted text clipped - 9 lines]
> > first place, or whether it is displayed, but perhaps with a non-obvious
> > name?

That kind of information (flash EV comp, lens name..) is stored in a
chunk of EXIF data called MakerNotes, which are defined by the
manufacturer. Not all software knows how to decode these MakerNotes.

For instance: Here's a list of Canon MakerNote tags.
<http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html#ShotIn
fo> Note the FlashExposureComp tag. Put this tag into google and
discover that all the different manufacturers put this tag in a
different place in their MakerNote.

One wishes EXIF had been further standardized before letting the
manufacturers go wild with it.

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