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Old Feb 23, 2006, 2:06 AM   #1
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I just got this flash and its exposure seems to be inconsistent even when pointed directly at the subject. But the bounce flash is totally unusable because it underexposes terribly in the automatic TTL setting. Look at this shot taken from only about 5 ft away bounced off of a white ceiling. Does anyone know what I am doing wrong? Is this a problem with this flash or is the unit defective?


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Old Feb 23, 2006, 5:55 AM   #2
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Hard to say, if I remember right some people had really inconsistent exposures with Sigmas when I searched in Dpreview forum for comparison between Metz, Minolta and Sigma flash.

http://www.sigmaphoto.com/flashes/manuals/F08MA.pdf
Sigma's manual seems to be quite short, or doesn't flash really have more modes?

Camera is propably using ADI flash control as default so have you tried pre flash TTL?
(what I got from Sigma's manual flash seems to be designed for pre flash TTL use)

Also for bounce flash exposure is even harder because reflectivity of surface used for bouncing can varie greatly so in that pre flash TTL is best bet.
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Old Feb 23, 2006, 7:26 AM   #3
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I personally would not trust any third party flash with the KM DLSR models, unless the flash had a built in sensor the measure reflected light using it's own auto mode (the Sigma doesn't).

If you send the flash unit into Sigma, they might be able to get it working better. I remember seeing a post from someone on another forum that managed to get one working right in most conditions, after sending it back to Sigma twice (they got it right the second time around).

More recently manufactured units may have less of a problem compared to older units if Sigma had been updating the firmware in the flash as adjustments are made.

You may have the same problem with a KM flash unit, too (3600HS, 5600HS). KM can calibrate them for better exposure if you get one that's too far off.

If you're not using an ADI compatible lens (8 contacts versus 5), make sure to change your camera to use pre-flash TTL.




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Old Feb 23, 2006, 11:30 AM   #4
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Thanks, but the pre-flash TTL shots come out even darker, basically pitch black. There are no modes to adjust for bounce flash.Camera automatically goes into bvounce flash mode when flash is lifted. I get the feeling this unit is defective. There is no way that it could be designed in this manner.
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Old Feb 23, 2006, 11:41 AM   #5
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It could be defective. But, even newer KM flash models can sometimes require calibration in order to work properly on a KM DSLR.

Flash Calibration for the KM 5600HS (D) and 3600HS (D)

Try your Sigma in FP mode. I've seen others report that FP mode was the only way they could get one exposing close to the way it should (and you're still likely to have some differences in exposure between straight on and bounced).

Newer serial numbers seem to have less issues than older ones, based on reports I've seen (probably because of updates to the strobe's firmware).

But, I personally wouldn't buy one for use on a KM DSLR. Trying to get the flash curve working just right so that the main flash is accurate based on a short preflash is hard for a manufacturer to do, without extensive testing and tuning with a particular camera model and available lenses.

Keep in mind that you don't have off the film metering during flash exposure like you did with film (the sensors used in a Digital Camera are too reflective for that purpose). So, a short preflash is needed to help gauge exposure for the longer main flash, and it's tougher than it appears to get it just right.




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Old Feb 23, 2006, 12:00 PM   #6
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P.S.

If you've already bought it and can't return it, I'd send it back to Sigma and see if they can update it. I saw a report from someone on another forum that said Sigma got one working OK after he sent his back to them twice. So, they may have an update that's better "tuned" for the KM DSLR models by now.

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Old Feb 23, 2006, 3:46 PM   #7
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I am going to Samy's camera tonight and will try the Sigma flash on another 5D, as well as try a Minolta flash on my camera to see if it is a flash problem or a camera problem. My 5D was refurbished and I have found autoexposure to be a little inconsisten and sometimes on the dark side. Will keep you posted.
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Old Mar 8, 2006, 11:42 PM   #8
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So, a couple of weeks later I have my replacement flash and wow, the bounce flash seems to be working fine, but the direct flash overexposes now. It seems to me that is basically fires at full power regardless of subject distance. So again the TTL system is not working. Sigma advised me to use the FP (High speed sync) setting. That, however, results in underexposed shots. What is going on? How come others seem to get good results with the km5D and Sigma EF-500 Super flash????
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Old Mar 9, 2006, 8:25 AM   #9
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I'm not so sure anyone is getting good results. ;-)

I see posts from time to time from users indicating they got one working OK. But, sometimes I see followup posts from the same users indicating that they were mistaken, depending on how they're using it (with flash range, bounce versus no bounce, etc. coming into the equation).

I did find one user that says his is working fine, after sending it back to Sigma twice for adjustments. He said that they got it right on the 2nd try. So, they may be able to reprogram one for better results, probably in the same way that KM can reprogram the 3600HS (D) and 5600HS (D) to work better on these cameras. It's my understanding that KM adjusts a "curve" related to preflash strength with their flashes for use on a 5D or 7D.

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Old Mar 9, 2006, 9:55 AM   #10
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I have one of these flashes, and it can be a bit hard to get right. Sigma does say in the included paperwork not to use TTL, but instead use HSS. this is not in the manual, but in an addendum in the packaging. I have found it to work better when it is not mounted to the camera. I also have many shots underexposed using TTL, I think it is more related to flash timing than brightness (the flash fires before or after the aperture is at its widest). I am still working on it, and only have a couple dozen shots using it ATM. Probably ~ 1/2 of the shots I've taken so far are exposed properly. I guess it's time to break out the manuals....:idea:

Anyhow, I'll keep you posted.
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