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Season's Greetings!
Well, since I haven't used this flash ON-camera yet, not sure if I would have the same fast shut-off issue. However, I do have an UNDEREXPOSURE (or SYNC) issue using the following set-up:
On the Pentax K-5:
Lens: Pentax DA 16-45 at 19mm (Approx. 10 ft. from subject)
Flash in Wireless Mode: Off
Manual Mode: 1/125 sec at f/9 ISO 200
Built-in Flash Mode: On at -0.7
Quality: RAW + JPEG Fine

Umbrella Flashes:
Metz Mecablitz 50 AF-1 at Full Power(1/1) Servo Mode into a 44” white umbrella approx. 5 ft. from subject at camera right (Main light)
Sunpak Auto 323 Super at ISO 200 Manual Full Power into a 40” white umbrella approx. 6 ft. from group at camera left (Fill)

The resulting image looked at least a half stop under-exposed (both on K-5 LCD and my display in Photoshop, prior to correction). However, I did not want to either open the aperture (would lessen DOF)or increase the ISO, and I could not really move the umbrellas any closer or they would have intruded into the image. My question is: Am I using the correct K-5 settings to allow proper flash Sync using the K-5's built-in flash as a "slave"? Thank you for any expertise!

[SOldBear]

My question is: Am I using the correct K-5 settings to allow proper flash Sync using the K-5's built-in flash as a "slave"?

How can you use the built-in flash as a "slave"? By definition, a "slave" flash is a unit triggered by another flash. The triggering flash is called a "control" or a "master" flash. The camera's built-in flash, if used, can only be a "control" or a "master."

I now assume you're using the built-in flash as a master.

The slave flashes are the Metz Mecablitz 50 AF-1 and the Sunpak Auto 323 Super. I assume they are triggered by optical slave (can be built-in, I don't know the 50 AF-1 and the term "servo mode").

My question: can the optical triggers ignore the preflash strobe from the K-5's built-in flash? If not, the slave flashes are triggered by the preflash strobe, and fire before the actual exposure. The light from the slave flashes have no effect on the exposure.

To verify this, run 2 experiments:

1. Have the same setup in front of a mirror, and take a photo of the mirror. It will be obvious whether the flashes fire during exposure.

2. Have the same setup, but set the K-5 in 2 second (self-timer) delay mode. The preflash strobe of the built-in flash will fire 2 seconds before the shutters open. You can tell whether the slave flashes are trigger by the preflash strobe of the built-in flash. If they do, and if they recycle fast enough, they may fire again 2 seconds later during the actual exposure. But if there is no 2 second delay, the slave flashes will not fire during actual exposure because there is not sufficient time to recycle.

[MRRiley]

Posts split off from thread discussing a diff Metz 50AF-1 issue

Mike
PF Moderation Team

[mattdm]

The slave flashes are the Metz Mecablitz 50 AF-1 and the Sunpak Auto 323 Super. I assume they are triggered by optical slave (can be built-in, I don't know the 50 AF-1 and the term "servo mode").

"Servo mode" is metz's term for a preflash-ignoring "dumb slave" mode, as opposed to its normal pttl slave mode.

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SOLDBear and Matt,
Yes, I mis-spoke about the K-5 built-in flash as "Slave", as I was also confused about the terms "Master", "Control" on the K-5, as well as what the difference is between the Metz 50's "Servo" and "P-TTL" modes. Thanks to your clarifications, I think I get it now!I will indeed try the two experiments you suggest. I also understand that using radio triggers (without the K-5 built-in flash) would also solve the underexposure problem, as would a dedicated light kit like those from elinchrom or profoto. Have a Happy New Year!