Which external flash as AF assist light?

[PhotoKratky]

The Manual of the my H4D states that, by setting a custom funtion, I'm able to do the following:

"External flash activates the AF assist Illumination projected by a suitable attached external flash unit. When detached, however, the integral system is automatically used."

Question is, what would be a "suitable attached external flash unit"? Reason I'm asking is that I usually use the internal AF assist light, but as soon as I attach the camera to a ring flash, only the backside of the ring flash is illuminated instead of the model's face. Maybe someone can share his or her experiences with using external flashes as an AF assist light.

[Buddy]

i can fully understand your problem, having a Bron ring flash myself, but never used it as such with H cameras. In deed the camera AF illumination light won't go through the collar of the ring flash as you describe it. To attach an external flash to the camera on the side with the flash cable might be a solution (but the hole setup will get heavier and more clumsy) and you probably cannot mount the flash on the hot shoe, since there you want to mount the flash trigger device...
I guess with H cameras the older Metz flash systems using a dedicated H-Metz socket will do the trick, but I am not sure. A Nikon flash will only work in manual mode with the flash cable connected. I could try later with this if the AF light would work with the Nikon.
The other question remains if you really need the H AF light in addition to the ring flash's modeling light? My Bron ring flash has 10 x 20 Watts of modeling light, which is ok for focusing.

[PhotoKratky]

Thanks for your reply, I'll look into the Metz flashes. If you could give the Nikon Flash a try, it would be great...

As for getting heavier and clumsier, yes, but an H4D, a 120/4 and a ring flash has me working from a tripod anyway...

As for the modelling light, yes again, but I only have the first version of the Profoto ring flash which sadly lacks a modelling light...

[Buddy]

Sorry to say, but after checking with my H6D-100c and a Nikon 910 connected via flash cable and in manual mode, it just doesn't work with the focus light from the flash after having set the menu item under AF "focus light from external flash". Even in such setting it will take the focus light from the camera....maybe works with the old Metz.

Don't want to make a big foss about using ring lights for portraiture, butt he big problem with ringflash is that the same side shadows that increase "roundness" in limbs posed at 90° to the lens' axis also produce ugly smudges of side shadow from anything that sticks out *towards* the camera.
That is the cause of grimey looking shadows seen either side of noses in square-on shots, for instance.
Apart from the nose, the rest of the face is fairly flat, of course, and this is the reason that ringflash glamour portraiture requires pretty heavy make-up to provide adequate face shaping. Without it the frontal lighting is not attractive, any more than ANY flash on camera ever looks good, unless the model herself looks good.
Now this is all fine and good if you are working with professional models who are perfectly used to coating themselves with opaque face paint, but the normal girl next door may not be happy about an excessively 'tarty' look, but without that make-up she will definitely NOT be flattered by a ringflash used up close.
The ringflash is still an ON-CAMERA, flash and you can screw-up just like a pop-up if you don't accomodate its inherant negative characteristics.
To recap: To get glamour from the ringflash you need to:

- specifically pose arms and legs at 90° to lens axis in full length shots.
- apply make-up in close ups to clean up the sides of the nose and provide face shaping/modelling.

And Keep the nose down so that it isn't lit from underneath.

Just a few hints from my experience, but maybe you know all this already...I am using the ring flash mostly in combination with a beauty dish not directly from the camera axis. But this is off course not the original idea of the ring light anymore...

Sorry, i didn't want to lecture on the topic, but this might be interesting for other readers here as well.

Let us know when testing with a Metz.

[PhotoKratky]

Thanks for checking and getting back to me about the Nikon flashes... 

As for ring flash and portraits: You are right, of course, regarding flat light and tarty look. However, I don't use it as the main light but as an on-axis fill to open up the shadows created by my key light. Might as well put a big Octa behind me and get rid of the ring flash in the future...   

[PhotoKratky]

To follow up on this: While TTL works nicely with the SCA adapter and a Metz 44 MZ-2 (including automatic zoom of the flash reflector when you change the focal length of the lens), I could get the flash to fire as an assist light.

When set to "focus light from external flash" neither the camera nor the flash emits an assist light. Maybe there is a hidden setting on the flash I have yet to find, but right now it does not work...