Learning about the 40d+Flash

Hey Guys, I'm fairly sure this is the right place for this, so here goes.

I have a canon 40d, and a bower sf035c flash that I picked up not too long ago, and haven't used it all that much honestly. I typically keep the camera on AV if I'm just shooting wildly, and I've noticed that the camera doesn't change the shutter speed to acknowledge the flash. It still keeps the SS at 0"6, or longer. This kind of defeats the purpose of my flash. Is there a way to use AV and still have the camera up the SS appropriately? or should I stick to using M when using a flash, which isn't a big deal.

Thanks!

I'll have to double-check when I get home, but I *think* the 40D has the option to restrict shutter speed between 1/60 and 1/250 when using a flash. If not, I'd think the best way would just be to stick with Manual when using the flash...

Nope, the 40D is acting exactly the way the Japanese engineers foolishly designed it to...failing to consider that Av can choose a very slow un-handholdable shutter speed even when the flash is mounted. It was not until more recent models that they offered CFn setting to have a range of allowable shutter speeds, so as to prevent hand holding blur in low light conditions and Av with flash.

Av sets a shutter speed suited to expose per ambient light, period. With or without flash, period.
Only with more recent models do you have any say, in speeds used with flash.

MuteGoose wrote in post #13809372
Is there a way to use AV and still have the camera up the SS appropriately? or should I stick to using M ...

C.Fn I -7 gives the option of Auto or 1/250 second in Av. Not much of a choice really.

Use your exposure meter (whether in manual or av/tv modes) to set the background exposure. Typically I put it at -2 EC or lower to saturate colors and / or make the properly exposed subject stand out more. Then adjust the flash, via a ettl flash exposure compensation or a manual flash setting, to properly expose your subject. It is really two different exposures in one and you need to adjust both independently to get the best results from your flash regardless of what shooting mode you are in. Leave either up to the camera and you are asking for point and shoot results.

Dustin Mustangs wrote in post #13809938
Use your exposure meter (whether in manual or av/tv modes) to set the background exposure. Typically I put it at -2 EC or lower to saturate colors and / or make the properly exposed subject stand out more. Then adjust the flash, via a ettl flash exposure compensation or a manual flash setting, to properly expose your subject. It is really two different exposures in one and you need to adjust both independently to get the best results from your flash regardless of what shooting mode you are in. Leave either up to the camera and you are asking for point and shoot results.

This still only works if you have enough ambient light to get a workable, ambient exposure. Which is the problem that the OP's hitting with Av mode.

Flash exposures handheld at .6" or longer can still have sharp subjects. The background will succumb to the long shutter and potentially blur due to shake, but your subject will have the flash duration as an effective shutter speed which is typically 1/1000 or faster.

Regardless, my point (that maybe wasn't obvious enough) is that when properly using a flash you can't ignore exposure settings. They determine what your background exposure is. Keep the exposure meter reading zero and you are telling the camera you want what it assumes is a non-flash effected background to be properly exposed according to its meter. This might require a high iso or, as in this case, dragging the shutter which is totally acceptable. A times you will have to do both to balance the exposure: http://strobist.blogsp​ot.com …-balancing-flash-and.html

MuteGoose, if you're new to canon ETTL, then I highly recommend reading this: http://photonotes.org/​articles/eos-flash/ It will explain exactly what you are seeing and why.

Briefly, when you are in Av or Tv mode, the Canon philosophy is to maintain proper ambient exposure using the shutter and aperture. The flash, as a default, is only used as a fill light and not the main light. So to get around this issue, you have two options:
1. Use Av and set a negative exposure compensation. This will speed up your shutter and darken the ambient. The flash's ETTL will then do its job and try to brighten up the subject as much as possible. However, the downside is that the exposure compensation only has a range of -2 to -3 stops depending on your camera.

2. Better option: use full manual mode. Set your aperture and set a shutter speed but let the flash do its own thing with the ETTL. Remember, shutter speed controls the amount of ambient light and aperture will control your DoF (and also impacts your flash power but the flash will compensate as long as it has sufficient power. Crank up the ISO if that's a problem.) Shutter speed will not affect the flash as long as you stay below 1/200. The higher the shutter speed, the less ambient light you have. The easiest way to get the right ambient exposure is to turn off your flash and take a test shot. If you like the amount of ambient you're getting, then turn the flash back on and take the pic. With a practised eye, you will be able to guess the right manual settings quite quickly.

The camera meters are reflective meters. They meter the light being reflected back into the camera lens from the scene. They might be good but they cannot measure light that the flash has not produced yet.