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Old Dec 2, 2003, 8:04 AM   #1
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Default Sigma 500 DG ST with 300D Underexposing


I shot about 50 shots (Jpegs) at a friends babies christening on Sunday with the above combination. I had the 300D set at 'P' mode (which i generally dont use as the lack of control drives me mad) as i had never use the flash before and tought i would let the camera do the work with E-TTL etc.... When i got home i transfered them to my Mac but some of them (Maybe 10) where extremely underexposed while others where ok. I managed to adjust the levels in PS 7 so that they appear acceptable but i would prefer they where correct to start with. Should i have used partial metering in TV/AV mode....? I know the 300D has problems with underexposing with the built in flash but does it effect external flash as well...? What mode/metering etc do you guys use...? Another thing is there a way of knowing how many stops one may be underexposed by viewing the levels histogram in PS 7 and is there a chart that sort of maps out exposure stops compared to levels....? Its hard to explain what i am getting at and hope its clear.....!

Thanks in advance

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Old Dec 2, 2003, 9:28 AM   #2
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Whenever you shoot flash with the P mode, the camera metering system attempts to properly expose the subject (wherever the focusing occurs) and disregard the background. Often, it can be fooled by surroundings, other objects, etc. When you compose your shot, are you aware of what the camera chooses as the focus point? This is very important as it may focus on the dark chair instead of the subject's eyes and will result in an exposure mismatch. In general the metering and focus system works fine 90% of the time, but there are times when it is fooled and this is where you must know when and how to adjust for that.

There is an excellent article on flash photography with EOS cameras at http://photonotes.org/articles/eos-flash/ which will provide you with some very good information on flash photography in general. Couple that with a good grasp of the exposure metering and focus controls (including FEL) of the 300d and you should be able to conquer your exposure issues.

Happy shooting.
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Old Dec 2, 2003, 9:35 AM   #3
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i was going to send him there myself too. what a system. but its fairly easy to work with/around once you have an idea why it does what it does. this explains it well.
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Old Dec 2, 2003, 11:05 AM   #4
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Thanks guys, i have a nights reading ahead of me.... :? Looks like a very comprehensive article. To be honest with you i am not a big fan of flash photography but at the minute cant afford L lens (unless the boss buys one for me ). I have a 50mm f1.8 but on the day i assumed i would need something wider and hence the 18-55 with average aperature....!

Thanks again

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Old Dec 2, 2003, 1:27 PM   #5
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BTW an underexposed image is usually acceptable since you can adjust the level as you described... an overexposed one is unrecoverable most of the time.

Also with the 300D you don't have Custom Functions to worry about, but for other cameras there's another article of interest: http://photonotes.org/reviews/sigma-ef-500-super/

* note this is an older flash and may not apply to the newer 500DG Super (or your ST)
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