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Old Feb 9, 2004, 2:06 AM   #1
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Default Canon 10D Tv changes with flash activation...

Hi,
I have noticed that when using the creative zone of my Canon EOS 10D, and flash activated, the Tv changes automatically to 1/200 from any higher value than 1/200. Is this a bug or a system feature for the 10dD. I dont see any reason why (even in full manual mode) the Tv should be linked to the built in flash.
Can some of you, more experienced, throw some light on this issue??
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Old Feb 9, 2004, 4:30 AM   #2
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This feature is normal: the shutter speed will change to 1/200s when a flash is attached, and it's charged: 1/200s is the camera's highest X-sync mode with flash. If you want to use faster shutter speed select FP or High-Speed sync on your flash; However be careful, you'll be decreasing the flash output power this way which will limit your distance, and the reason why the camera is forcing you to make an extra step in this shutter speed selection: @ 1/500s for example, the flash range is reduced by more than half compared to 1/200s, and even more with each shutter speed increase!

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Old Feb 9, 2004, 4:57 AM   #3
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Hi,
Thanx for the valuable info. But since I am using a built-in flash, Is there a way to change to the high speed sync mode and set the sync speed?
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Old Feb 9, 2004, 5:01 AM   #4
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No!

I guess the charging circuit in the built-in flash is too tiny to sustain longer high-speed stroboscopic burst... beside it's already pretty weak to start with and 1/2 of that output certainly won't help!

BTW you do not need a high shutter speed to freeze an action: the flash burst is incredibly brief that you can freeze an action even @ 1/30-1/60s... If you are not, then your flash is either not powerful enough for the ambient light or you are out of range (ie too far), where a higher shutter speed will come into play. ops:
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Old Feb 9, 2004, 7:19 AM   #5
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I just wanted to add two things.

If you really want high-speed sync, you can buy an external flash. I know mine has it (550EX) but I believe that other, cheaper models have it too.

This is more a question than an answer. If you try to use 1/30 or 1/60th to stop action with the flash, I presume that the ambient light has to be quite low, right? If not, it would supply enough light to record the action, right?

Eric
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Old Feb 9, 2004, 8:21 AM   #6
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Quote:
Originally Posted by eric s
This is more a question than an answer. If you try to use 1/30 or 1/60th to stop action with the flash, I presume that the ambient light has to be quite low, right? If not, it would supply enough light to record the action, right?
... You're correct but I wouldn't phrase it that way.

Since the short flash burst can freeze the action, I would use the advantage of a slower shutter speed to lighten up the background for example rather than blackened it out with a higher shutter speed... ie a fill flash with more background if that's the intention.
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Old Feb 10, 2004, 4:59 AM   #7
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But wont the image captured of the subject/background also depend on the Av. Is it recommended that we move to Tv mode and let he camera choose the Av automatically.
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Old Feb 10, 2004, 5:13 AM   #8
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It depends what you want to control essentially:
1. Tv if you want to fix the speed
2. Av if you want to fix the aperture
3. and Manual if you want to control both with flash
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Old Feb 10, 2004, 8:12 AM   #9
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Quote:
Originally Posted by eric s
I just wanted to add two things.

This is more a question than an answer. If you try to use 1/30 or 1/60th to stop action with the flash, I presume that the ambient light has to be quite low, right? If not, it would supply enough light to record the action, right?

Eric
Eric,

Anytime you shoot with the shutter speed slower than the X-synchro speed, you want the ambient light to be mixed with flash light. NHL is right about the flash synchro at any speed can minimize the motion of the subject since flash duration is very fash, up to 1/10,000. When you use slow synchro mode, you can increase DOF since the aperture value will be smaller, the question is: how much ambient light do you want to be include in your picture and how much the flash coverage. At the default synchro speed (1/60), the flash light will dominate the scene (100%), at any speed slower than that, the % of flash coverage will be reduced and introduce the existing light. If you use one of the flash meter which has the flash analysis mode (such as the Sekonic 608 or the Minolta flash meter 5 or 6), it will show the % of the flash coverage on the meter, by reduce further more on the x-synchrso speed, more % of the abient light will be result in the final exposure. This is one of the joy of flash photography, and you will appreciate very much the useful of the flash meter, practicing with more flash shots, you will undertand why most of the commercial outdoors pictures today (85%) are made with studio flashes.

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