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03-30-2008, 05:33 PM   #1
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K10d and inbuilt flash

I know that flash has been mentioned a lot on this forum but I am having a bit of an issue with the inbuilt flash. When coupled with the 16-50mmDA* lens at 16mm in AV mode(at any F stop) the shutter speed is set to 1/30 and it will not alter till the lens is zoomed out. Is this not too slow? Never noticed it this slow on the *ist DS.

03-30-2008, 05:51 PM   #2
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my DA 18-55 is the same. i am a newbie, and i'm a little puzzled too. At, say, 55mm with flash raised, the shutter speed is set to a specific value - lets say 1/80 - , irrespective of what i do to the aperture. if i wind the zoom back to 18mm, the shutter speed shifts to 1/30, but again this remains constant even if i change aperture size.

i believe the P-ttl system looks at the focal length set, but why doesn't it adjust shutter speed to suit aperture settings? presumably the flash intensity is adjusted automatically instead?

flash photography is one area i haven't been able to get to grips with as yet on the K10 (granted, i've only had it for 4 days!). sometimes the full frame is illuminated, other times only the centre subject, and -on this lens at least- i get brighter exposure with a smaller aperture. can't figure it out yet.
03-30-2008, 06:05 PM   #3
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mounted the kit lines on the k10d, and it was adjusting Tv values when i was zooming in and out, in P and Green Mode. flash comepenstaion was set to 0,

the K20 was doing the same (w/ the da* 50-135)
03-30-2008, 06:08 PM   #4
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yep, it adjusts based on zoom setting rather than on aperture setting. just not sure why.

03-30-2008, 08:09 PM   #5
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I just purchased a Sigma EF 530 DG Super .... and I find that the flash adjusts power to the zoom you have selected ... everytime the zoom length is changed the flash compensates ... but the shutter speeds remains at a set speed ... unless you change to high-speed sync or any of the other options I haven't read up on yet.

So it is not just the on-board pop-up that does it.
03-30-2008, 11:43 PM   #6
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QuoteOriginally posted by saladin Quote
At, say, 55mm with flash raised, the shutter speed is set to a specific value - lets say 1/80 - , irrespective of what i do to the aperture. if i wind the zoom back to 18mm, the shutter speed shifts to 1/30, but again this remains constant even if i change aperture size.
Yes, this is exactly how it is supposed to behave.

QuoteQuote:
i believe the P-ttl system looks at the focal length set, but why doesn't it adjust shutter speed to suit aperture settings? presumably the flash intensity is adjusted automatically instead?
In normal flash mode and in most flash photography in low light condition, the main exposure illumination is from the flash - which is affected by the aperture and flash power. And notice that I did not mention shutter speed; as the shutter speed does not matter as long as it is below the flash sync speed. What the shutter speed does affect is the ambient light exposure (light already present without the flash).

So what your camera is trying to do is to use the slowest shutter speed possible while avoiding the camera shake - i.e. using the 1/(focal length x crop factor) rule for hand held shots. This would allow as much ambient light as possible as limited by the shutter speed to avoid camera shake. The flash exposure itself is automatically adjusted by the P-TTL metering.

Now you can override this behavior by using "Slow Speed Sync" mode. Here, the 1/focal lengthxCF rule no longer applies. The camera would use as low a shutter speed as possible to get the correct ambient light exposure. This usually means you need a tripod to avoid camera shake.
03-30-2008, 11:55 PM   #7
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QuoteOriginally posted by nosnoop Quote
Yes, this is exactly how it is supposed to behave.



In normal flash mode and in most flash photography in low light condition, the main exposure illumination is from the flash - which is affected by the aperture and flash power. And notice that I did not mention shutter speed; as the shutter speed does not matter as long as it is below the flash sync speed. What the shutter speed does affect is the ambient light exposure (light already present without the flash).

So what your camera is trying to do is to use the slowest shutter speed possible while avoiding the camera shake - i.e. using the 1/(focal length x crop factor) rule for hand held shots. This would allow as much ambient light as possible as limited by the shutter speed to avoid camera shake. The flash exposure itself is automatically adjusted by the P-TTL metering.

Now you can override this behavior by using "Slow Speed Sync" mode. Here, the 1/focal lengthxCF rule no longer applies. The camera would use as low a shutter speed as possible to get the correct ambient light exposure. This usually means you need a tripod to avoid camera shake.

thank you, nosnoop. excellent clarification.
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