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04-06-2011, 06:33 AM   #1
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AF Assist on Bracket mounted flash?

Does anyone know if there's a way to activate AF assist on an AF540 flash mounted off-camera (K20) on a bracket with a cable connection to the camera's hot shoe?

The manual says AF assist only works when the flash is mounted on-camera and this does indeed seem to be the case. I'm hoping someone has a work around.

I shoot a lot of large events and am experiencing a disturbing trend toward extremely low lighting, making auto-focus time-consuming, sometimes impossible and always a bit embarrasing as we wait while the lens hunts back and forth.

I would greatly prefer not to give up the camera-rotating bracket because it allows me to quickly switch from portrait to landscape without having to fiddle with flash, which I almost always bounce off the ceiling.

Any suggestions would be greatly appreciated.

04-06-2011, 12:48 PM   #2
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Does your cable have 5 connectors? In other words, does your cable support p-TTL (similar to this)?

If it does, AF assist light will work. The camera and the flash don't know there is a cable between them.

Aiming the AF assist light with the flash attached to a bracket can be a problem, however.
04-06-2011, 03:25 PM   #3
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QuoteOriginally posted by SOldBear Quote
The camera and the flash don't know there is a cable between them.

Aiming the AF assist light with the flash attached to a bracket can be a problem, however.

That aiming problem is, unfortunately, a big one if your bracket (like my Manfrotto) extends a ways.
04-06-2011, 03:56 PM   #4
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I use the Pentax F5P extension cord which is a 5-pin cable. However, the Pentax Off-Camera Shoe Adapater F, and the Pentax Hot Shoe Adapter-F both have only 4 pins. Then again, the K20 hot shoe has only 4 pins, so this confuses me.

You do make a good focusing point though about aiming the AF assist light with the flash attached to the top of the bracket. Hadn't thought of that. Thanks.

But, this brings me to my second issue: I've never had any difficulties with P-TTL until recently. After about 2 hours of fairly reliable P-TTL shooting , the AF 540 seems to go haywire and P-TTL disappears from the menu. When this happens, I frantically double-check or re-seat all the connections, shut everything down for as long as I can, change the flash's batteries and sometimes change the camera's memory card in case it might be filling up. Sometimes these things work immediately and P-TTL reappears; Sometimes they don't and I start shooting in manual. It's a crap shoot -- very unpredictable and very very scary.

Am I doing something wrong or is the AF540 perhaps on its last legs? It's about 4 years old and getting a workout at these events.

04-06-2011, 04:27 PM   #5
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QuoteOriginally posted by marianne718 Quote
I use the Pentax F5P extension cord which is a 5-pin cable. However, the Pentax Off-Camera Shoe Adapater F, and the Pentax Hot Shoe Adapter-F both have only 4 pins. Then again, the K20 hot shoe has only 4 pins, so this confuses me.
When you count GND as a signal, they all have 5 connectors. GND is the sides or at the sides of the hotshoe/hotfoot. For example, this Pentax TTL foot has 4 contacts, not 3. The GND is on the side (green arrow):



QuoteOriginally posted by marianne718 Quote
I've never had any difficulties with P-TTL until recently. After about 2 hours of fairly reliable P-TTL shooting , the AF 540 seems to go haywire and P-TTL disappears from the menu. When this happens, I frantically double-check or re-seat all the connections, shut everything down for as long as I can, change the flash's batteries and sometimes change the camera's memory card in case it might be filling up. Sometimes these things work immediately and P-TTL reappears; Sometimes they don't and I start shooting in manual. It's a crap shoot -- very unpredictable and very very scary.
It sounds like dirty/loose connections. I'd dissemble the flash as much as I can and reseat all the connectors. Removing the foot is pretty simple, just remove the 4 small screws at the foot of the flash.

QuoteOriginally posted by marianne718 Quote
You do make a good focusing point though about aiming the AF assist light with the flash attached to the top of the bracket...
One possible way to get around the problem is to choose the focus sensor where the beam shines. I have a handle-mount Metz with AF assist lamp. The AP assist lamp sits on the camera, attached to the hotshoe, but for close distance (say, less than 12 ft), I have to choose the focus sensor above the center one.

Last edited by SOldBear; 04-06-2011 at 04:35 PM.
04-07-2011, 04:55 AM   #6
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Thanks. I'll try the disassembling thing and hope for the best.

What should I use to clean the external contacts? I've only used a spare lens cloth.
04-19-2011, 05:32 AM   #7
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Well, I guess deep down in my gut I knew that the problems I was experiencing with the AF-540 (e.g., the issue with the AF assist beam, the random disappearances of P-TTL) were in fact signals that the end was near. The flash went completely bonkers on me during my last shoot of a baptism party. 15 minutes into the event, the LCD screen started blinking and randomly cycling through the modes, and wouldn't fire reliably in any mode. A change of batteries and 5-minute time-out did nothing to resolve the problem. P-TTL disappeared altogether and to this day, has not returned. Luckily, I had my 360 with me as backup and it served me well enough through the remainder of the party.

The flash is only 3 years old yet is evidently a goner. As much as I loved working with the AF-540, I am crushed that it crapped out on me so soon. I'm considering replacing it with the Metz 58-2 but am somewhat intimidated by what I've read about the complicated menu system, not to mention the cost of the external power pack (which I was planning to purchase for the AF-540).

Any ideas, suggestions, or reassurances that the Metz 58-2 will be worth the effort and cost? The other flash I'm considering is the Sigma EF 610 DG Super, for the good price and decent comments about it. I have another shoot coming up on April 30 and need to make a decision, fast.

Last edited by marianne718; 04-19-2011 at 05:49 AM. Reason: accidental omission
04-19-2011, 07:33 AM   #8
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This would certainly be one area that would greatly benefit from the AF-assist beam (K-7/5) still firing with a flash attached, that was mentioned in another thread.

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