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04-22-2010, 07:16 AM   #1
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AF160 Flash Unit

I have a working Pentas AF 160 flash unit from my old Pentax ME Super. I am considering purchasing a Kx DSLR and understand that my K mount SMC lenses and Tamron K mount lenses will work but will require manual focusing. What about the AF160 flash unit. Can it be used with the DSLR?

04-22-2010, 07:32 AM   #2
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The Kx won't do TTL but if you can change the output of the flash manually, you can use it (or any other safe flash) with your Kx. By Safe I mean the trigger voltage. Some older flashes have trigger voltages in the 100s of volts. Most modern flash units are 6-12 volts (the voltage of the batteries is not at issue here).

04-22-2010, 12:14 PM   #3
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Yes, the AF160 works with current batch of Pentax DSLRs. I can't recall the trigger voltage, but I did measure mine and found it safe.

Of course it works in manual mode. But A mode works as well. Set the shutter speed at X or 1/180 or lower, match the ISO and aperture settings on the camera body and on the flash. Works great.
04-23-2010, 05:16 AM   #4
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Bear,

I have a multimeter. Can you tell me how to measure the trigger voltage? I assume that if my unit is out of bounds I can damage the camera?

04-23-2010, 06:09 PM   #5
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Can anyone here describe for me the method to measure trigger voltage? thx
04-23-2010, 06:21 PM   #6
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QuoteOriginally posted by gkamieneski Quote
Can anyone here describe for me the method to measure trigger voltage? thx
Here is a good page about flash voltages. The method to test is down the page a bit.
04-23-2010, 06:25 PM   #7
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You need a digital multimeter. Set it to VDC (DC voltage), select 2000V (if the multimeter is not auto-range).

With new battery cells in the flash, turn the flash on to charge. Make sure the "ready" lamp is on.

Measure the voltage from the ground terminals on either side of the flash's foot to the center pin of the flash's foot.

That is "trigger voltage."
04-23-2010, 07:45 PM   #8
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I registered 4.8 volts. Does that make sense? Also, maybe I have forgotten, but what does it mean that the K-x cannot do TTL? thx


Last edited by gkamieneski; 04-23-2010 at 07:52 PM.
04-23-2010, 11:55 PM   #9
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QuoteOriginally posted by gkamieneski Quote
I registered 4.8 volts. Does that make sense? Also, maybe I have forgotten, but what does it mean that the K-x cannot do TTL? thx
4.8V sounds reasonable. Mine reads 3.8V.

TTL flash metering, available with the *ist DSLR series and some film cameras, requires additional light sensors to measure light reflected from the sensor during exposure. When the sensors determine there has been enough light, they signal the camera to turn off the flash. A nice thing about TTL flash metering is that it doesn't matter what lens is attached to the camera, even a pin-hole, the exposure is still correct. The flash unit and the camera body need to communicate and thus the flash unit needs to be "dedicated."

p-TTL flash metering, starting with the K-series (K10D, K100D, ....., K-x, K-7), uses the same light sensors in the prism. The flash emits a weak pre-flash strobe before the mirror goes up. Light reflected from the scene is then measured and flash output needed is computed. Then the mirror goes up, shutter opens, and the flash emits the main strobe with the output as previously calculated. Of course the flash needs to be "dedicated." Not only that, since the metering is done with the lens at full aperture (otherwise the pre-flash strobe would need to be powerful), the camera needs to communicate with the lens as well. This is why p-TTL is not possible with manual (pK mount, M42 mount) lenses.

The AF160 works in manual and auto mode (using light sensor of the flash unit). In auto mode, set the flash to auto, match the ISO setting and the aperture setting on the camera as indicated on the flash, shutter speed 1/180 sec (X) or slower, then shoot. The flash's light sensor will measure the light and shut off the flash's output when it determines there has been enough light.

I have two Pentax 540, but for various reasons I don't use p-TTL unless when I absolutely have to (e.g. high speed, trailing curtain).

I almost forgot: I've been using flash units with trigger voltage up to 24V with my K10D bodies without any problem.
04-24-2010, 09:42 AM   #10
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Bear,

Your AF160 sounds different from mine. Mine has an "M" setting and Green and Red settings that are valid in the guide chart on the back.

Also, when I look at the hot shoe on the K-x, I do not see a matching center post contact. Is that because the photos of the product I see have a hot shoe "cover" in place?

Thanks. You've been very helpful to someone who fades in and out of this hobby every so many years.

Last edited by gkamieneski; 04-24-2010 at 09:49 AM.
04-24-2010, 10:23 AM   #11
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The Kx has a flash shoe, if you're not seeing the contacts, it probably is shown with the cover in place. To use it, this may help...

http://www.pentax-manuals.com/manuals/accessories/af160.pdf

Password = Pentax

Or is it one of These

http://www.pentax-manuals.com/manuals/accessories/af160sa.pdf

04-24-2010, 05:00 PM   #12
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Jeff,

Mine is the first AF160 you listed. Looks like I will be able to use it some with a K-x as I measured trigger voltage at only 4.8v. I just wanted to compare the hot shoe contacts with those on my ME Super where the flash has formerly worked.
04-24-2010, 06:15 PM   #13
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QuoteOriginally posted by gkamieneski Quote
Jeff,

Mine is the first AF160 you listed. Looks like I will be able to use it some with a K-x as I measured trigger voltage at only 4.8v. I just wanted to compare the hot shoe contacts with those on my ME Super where the flash has formerly worked.
It'll work.. The other two contacts on the camera don't matter, they aren't going to do anything, only the center one that triggers the flash. At 4.8 volts you are more than safe. The suggested standard for maximum assured safety use to be 6 volts and there are devices (Wein flash trigger) that can be used to allow the very high voltage flashes to be used on a modern flash shoe.

04-24-2010, 11:43 PM   #14
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QuoteOriginally posted by gkamieneski Quote
Mine is the first AF160 you listed. Looks like I will be able to use it some with a K-x as I measured trigger voltage at only 4.8v. I just wanted to compare the hot shoe contacts with those on my ME Super where the flash has formerly worked.
Yup, that's what I have. I don't use it much (yes, there is indeed such thing as having to many flashes ). But once in a while I'm still using it to trigger optical slaves.

06-02-2010, 08:02 AM   #15
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Soldbear,

I finally got around to trying this. I need to shoot a band concert in an auditorium and with the K-x I can use the Stage Lighting program mode, or I can use the camera's flash, or I can try the AF160 on the hotshoe.

I tested the AF160 shooting M at ASA 400 and F5.6 and turning the AF160 to Auto Red. This worked well. How would I use this flash with the flash set to M though? I'm already using the camera in M mode. thx
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