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02-21-2011, 08:58 AM   #1
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AF360 underexposure

I've been using my AF360 on my K10 and occasionally on other bodies. On all of them, it consistently underexposes when shooting close subjects well within a comfortable flash range (often under 10'). The apertures are usually f5.6 to f8, again comfortable for the range.

Direct flash is about one stop under, bounce is worse.

Here's the modes I've tried with cameras set to X synch and using a range of lenses. Results were identical whether used on Auto with A series MF lenses or DA lenses on either Auto or P-TTL. Green mode seems to be a bit better on the K10, but still about a half stop dark.

P-TTL (underexposed)
Auto (underexposed)
Manual (OK when dumping full flash)
Slave on Auto (underexposed, both flashes fired)

I've been careful to ensure that ISO, exposure compensation and aperture match between camera and flash.

Other settings used:

careful not to be on wireless mode, channel 1, when on auto aperture matches camera, format set on 35mm, auto or manual zoom, exposure compensation on both camera and flash set to zero.

Only full power manual mode, EV +1 exposure compensation (or more) or faking the flash out when on Auto by setting the lens at a wider aperture than the flash setting, has produced decent results.

Any idea what is going on?


Last edited by Rusty Rat; 02-21-2011 at 09:18 AM.
02-21-2011, 10:56 AM   #2
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QuoteOriginally posted by Rusty Rat Quote
Any idea what is going on?
flash is metered when lens is wide open and flash itself is not fired at the actual power that will be used during the actual shot - actual shot is done w/ lens stopped down and flash at calculated power which is usually more than used during metering... now that Pentax metering was not state of the are at the time of K10D and also flash like AF360 might also not be firing exactly as body thinks it will there is no wonder that you might actually remember to dial in exposure correction on the flash... just my 2c...
02-21-2011, 11:55 AM   #3
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Thanks, basically what I thought too, just plug in the EV +1 and move on . . . .
11-16-2013, 11:51 AM   #4
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I know this is an old thread but I was researching this concerning my new k30.
I was hoping to see a difference with the new camera but I think it is now a shortcoming of the flash. I wonder if the new "II" model does any better...

11-16-2013, 12:07 PM   #5
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My AF360 is working fine on ist ds and K-01 in various modes.
I was doing portraits indoors today, ist ds with AF360 in slave mode, "A" mode, on a separate tripod, bounce off ceiling. All OK.

I just ran a test on K-01 with AF360 in p-ttl, and all OK.

I wonder if your capacitor is down or something?
11-16-2013, 12:18 PM   #6
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Come to think of it, my istD didn't do this....

I have three AF 360 flashes... they all underexpose on my k-x and k-30... I no longer own the k20d.
I have not checked my k2000, I cannot remember if this was an issue on that camera.

I have a k-01 also, I will check it...
11-16-2013, 03:36 PM   #7
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I've run across an issue lately with using older flashes and a new AF camera. I don't know if this is also the case with this flash or not, but it's worth experimenting.

As it was explained to me, apparently many modern flashes put out a low power pre-flash followed by the main burst. If this doesn't synch up with the shutter curtain properly, then only the pre-flash is captured when the shutter opens. On my new camera, there's a "Commander" mode that allows the camera's flash to act as the commander for a slave unit. The mode is required to allow the flash to time up properly with the shutter. If other flash modes are used, then everything is underexposed as the main slave flash fires early before the shutter opens.

Try setting the flash to forward then rear shutter curtain synch to see if either one helps.

My AF360 worked fine when used on manual, which leads me to think shutter synch may be the issue. It probably didn't pre-flash when on manual.
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