7d flash question
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- JamesBoynton
Hi guys, recently started playing with the onbody flash on my 7d.
I have read on a number of sites that having the flash up in av/tv mode will make no difference to the exposure. An example of what i am reading is here (http://www.flickr.com/groups/ca... - "a flash will work as a fill light in Av and Tv, i.e. your camera still exposes as it would without the flash".
If thats the case I am having a problem, if I set to Tv and set my shutter and iso and get for example a f stop of 2.8... then I pop the flash up and the f stop goes up to around 4. Its almost like the camera is changing the exposure to take account of the flash.
I thought the settings stayed the same and then the flash brightness would be set based on the preflash?
Am I missing something here? any help would be great
James
- JamesBoynton0
Another example is here - http://photonotes.org/articles/e… - n Av, night and Tv (shutter speed priority) modes the camera meters for ambient (existing) light and fills in the foreground subject using the flash. It does not assume that the primary light source is the flash, and therefore the shutter speed it sets is the same as it would set if you weren’t using flash at all.
- For me it changes the shutter speed when in Av mode and pop up the flash.JamesBoynton
- jaylarson0
Aperture and flash power together are what determine the effects of flash. I have my d700 on slow synch which has a longer shutter speed to allow more ambient light, great for backlighted subjects. Couple that with the current ISO and aperture settings. That's why some people like ND filters so they can have shallow DOF for portraits, because aperture and flash strength are what determine the exposure from flash.
make sense?
- JamesBoynton0
Hi Jay yeah that does, cheers. I'm still unsure why it seems to change the settings just by popping up the flash, especially when all I read says the the settings should not change when using the flash... Hmmm