Built-in Flash in Aperature/Shutter Priority Mode

[kizersoze]

I'm using the 30D.

While in Av mode if I use the flash will the camera properly meter and adjust the shutter speed? Yesterday when I was shooting some photos the shutter speed didn't change when I opened up the flash and thought that was strange.

Instead I had to switch to Shutter Priority and set the shutter speed higher, but still the camera complained that the metering was off by blinking the Aperture Value.

I've only had the 30D for a few days and don't quite understand how the metering works when you want to use the flash in the "Creative" Zones.

Can someone provide me an insight?

Thanks in advance.

[DavidW]

For full information on flash with EOS cameras, read the EOS Flash "Bible". There's also some simpler tutorials over in the Small Flash and Studio Lighting forum. It doesn't matter that you're using the built-in flash - it's still an E-TTL flash run by the E-TTL II algorithm - it just lacks power and head adjustability (you can't swivel or rotate the flash).


The simple answer is that a flash photograph is two exposures in one - an ambient light exposure and a flash exposure. In Av mode, the camera continues to meter for the ambient light. Typical use of a flash in Av mode is for fill flash - "true" fill flash is somewhere around FEC -1 1/3 to -1 2/3.

Flash and Tv mode rarely makes much sense - you're still metering for the ambient light.


I can't entirely remember how flash operates in P mode - though, in essence, the camera sets a shutter speed between the sync speed and 1/60, so that you can still hand hold, chooses a suitable aperture, and attempts to expose correctly using flash whilst not worrying about the ambient light. I don't use P mode nor any of the "icon" modes on my camera at all. I'm predominantly an Av and M mode user, with a little bit of A-DEP and Tv.


If you want to take a picture with the flash as the main or only light source, go to M mode. Dial in a shutter speed at or just below the sync speed (which I think is 1/250s on the 30D, as it was on the 20D), and the aperture you want.

The 'needle' in the viewfinder will probably be blinking at -2, indicating that the ambient light exposure will be very underexposed, but the flash should expose correctly.


Unlike with an external Speedlite, it doesn't seem that you can confirm you have adequate flash power available using FEL (you get a flashing 'bolt' if there's insufficient flash power using a Speedlite), also you don't have a flash exposure confirmation light.

It's certainly worth experimenting with the internal flash, particularly as Speedlites in E-TTL mode work exactly the same way as the internal flash. However, if you're serious about flash photography, it's well worth considering a Speedlite. The 430EX isn't too expensive, and may be all you need, though I'm happy I've got a 580EX in my bag.



David

[Curtis N]

Originally Posted by kizersoze

Can someone provide me an insight?

Here's some insight.
Flash Photography 101

[kizersoze]

Thanks for all the input.

[DavidW]

Curtis - that was exactly the thread I had in mind. Thanks for posting it again, and for all the effort in producing it - great job.



David