Hexar AF: Maximizing the flash

[benji77]

Hi, I cant seem to optimize the flash (power), and get even lighting results with the Hexar flash. I must be reading the GN# wrong.

For example, if I have ISO 1600, and would like for fill flash onto a group of 2-8 people indoor (restaurant, building etc), would I have to set the aperture (A Mode) to F8?

I shot it wide open, and blew the subjects with flash they look like angels. :bang: I managed to save them in post processing, but would like to know what I am doing wrong.

Should high iso's be used with F4-F8's and the opposite for Low ISO (100 - 400)?

 

[pvdhaar]

No wonder your subjects looked like angels.. you really zapped them 🙂

At 100ISO, the HX-14 has GN=14. That means that at aperture F2, you can correctly light something 7m (20ft) away. The basic rule is Aperture=GN/distance.

At 400ISO, that GN=14 doubles to 28, and at 1600ISO, it doubles again to 56. For something at 7meters away, that would mean for ISO 1600 Aperture=56/7=F8. And for subjects at 3.5m (10ft or so), it's F16..

 

[benji77]

Thanks for the note.

Would it mean that my flash power now is dependent on the ISO?

In using my DSLR, I prefer a high ISO, roughly F4, and average power of the flash, this would allow for a nicely lit background, and not blacked out.

Wow, I really have to get this GN thing right!