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12-04-2012, 07:57 PM   #1
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problems with AF and external flash

I have an external vivtar flash and it wont fir consistently with auto focus. I need help in learning more about this issue. Thanks.

12-04-2012, 08:06 PM   #2
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If you would like meaningful replies, you'll need to express the problem clearly. You don't call your auto mechanic and just say, "My car doesn't work" and expect him/her to tell you how to fix the problem.

- List the models of the equipment you use: camera, flash, lens, accessories, ....

- Describe the condition of your testcase: camera mode, flash mode, AF mode, shutter speed, aperture,....

- Describe the symptom clearly. "wont fir consistently with auto focus" doesn't say much. What's your setup? How's the result: flash doesn't fire? Photos not sharp?

Last edited by SOldBear; 12-05-2012 at 08:42 AM.
12-04-2012, 10:57 PM   #3
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As noted above, flash issues can be hard to diagnose. There are so many different cameras with so many different flash capabilities. Couple that with so many flashes with so many compatible/incompatible features and you can imagine that the number of cases where things might not work right can be pretty huge!

At the very least, it would be good to know the camera model and the flash model. From there it may be possible to determine the common set of compatible features.

On a side note, there is also the possibility that your flash has too high a trigger voltage for your camera. This would be particularly true if your Vivitar flash was designed to work with older cameras and you are trying to use it on a modern dSLR. I own two Viv flashes from the early 1980s that I dare not mount to my K10D for fear of damage to the camera's electronics.


Steve
12-08-2012, 05:02 AM   #4
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I guess voltage depends on model. I have a Vivitar 285HV and an older one (packed now so I can't look up model number, but I think 2200). Both work great on both K-x and K 30. Voltage of the 285HV is somewhere around 7 or 7.5 if I remember correctly, it's been a while since I checked it. Seems the other one was around 5 volts. I measured both when I first got the K-x 2 1/2 years ago. General concensus is keep it under 25 volts I think...but I don't think voltage is the problem, if it were I think this thread would be named "Help my camera died"...

I'm guessing here but I'm thinking shutter speed. Pentax flash sync is 1/180 shutter speed, anything over that and flash will not fire, whether onboard or hot shoe. At least that has been my results with K-x, haven't done enough with K 30 and flash to have a definite answer. So if you're shooting in any mode that allows various shutter speeds, the only time flash will work is when shutter speed is 1/180 or slower. I always shoot in Manual mode, so I never have a problem. If I need to use flash, I set shutter speed to 180 and forget about it...but if you're shooting Aperture Priority or any other mode that will use various shutter speeds, any time shutter speed goes above 180 you will not have flash.

12-08-2012, 09:31 AM   #5
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QuoteOriginally posted by Paleo Pete Quote
I guess voltage depends on model. I have a Vivitar 285HV and an older one (packed now so I can't look up model number, but I think 2200). Both work great on both K-x and K 30. Voltage of the 285HV is somewhere around 7 or 7.5 if I remember correctly, it's been a while since I checked it. Seems the other one was around 5 volts. I measured both when I first got the K-x 2 1/2 years ago. General concensus is keep it under 25 volts I think...but I don't think voltage is the problem, if it were I think this thread would be named "Help my camera died"...

I'm guessing here but I'm thinking shutter speed. Pentax flash sync is 1/180 shutter speed, anything over that and flash will not fire, whether onboard or hot shoe. At least that has been my results with K-x, haven't done enough with K 30 and flash to have a definite answer. So if you're shooting in any mode that allows various shutter speeds, the only time flash will work is when shutter speed is 1/180 or slower. I always shoot in Manual mode, so I never have a problem. If I need to use flash, I set shutter speed to 180 and forget about it...but if you're shooting Aperture Priority or any other mode that will use various shutter speeds, any time shutter speed goes above 180 you will not have flash.
It will fire if you set the flash (hot shoe only) to HSS at speed higher than 1/180. You can use Av mode and HSS as fill flash in outdoor shots. Keeping in mind, the inverse square law, it would only be effective as long as the subject is close enough.

Last edited by aleonx3; 12-08-2012 at 10:42 AM.
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