Focusing and the Sigma 500 DG Super

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kmiragaya

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Karel
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Hello

I have a Sigma 500 DG Super flashgun and I've read that it only works with the central focus point on Canon cameras.

Does this mean that the focus assist light only works when you are using the central focus point or that the flash always gives priority to the central point when it's going to estimate the correct flash exposure in E-TTL mode regardless of what focus point I'm actually using?

Regards
 
kmiragaya said:
Hello

I have a Sigma 500 DG Super flashgun and I've read that it only works with the central focus point on Canon cameras.

Does this mean that the focus assist light only works when you are using the central focus point or that the flash always gives priority to the central point when it's going to estimate the correct flash exposure in E-TTL mode regardless of what focus point I'm actually using?

Regards
Click to expand...

Hmm. With Canon guns, the AF assist beam changes from narrow to wide when an off-centre AF point is selected. Easy enough to check what your Sigma is doing.

Some Canon lenses report focusing distance and this info is fed into the flash exposure algorithms, but I can think that it's of much use. It's only very crude anyway, something like close, not so close, and not very close at all. Compared to the pre-flash actual light data collected I would think it's neither here nor there anyway.
 
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