Rebel Hack and FEC

[Hellashot]

I just installed the hack firmware into my Drebel and tried out FEC. Taking a couple test shots in manual exposure with FEC at +2, the camera didn't seem to take the FEC into account asking for a slow shutter speed ending in a way over exposed image.

When I use FEC on my EX550 the camera takes it into account with the exposure meter. Am I doing something wrong or will in-camera FEC not be taken into account with the exposure meter?

[tim]

What are you expecting FEC to do? All it does is tell the flash to go a little brighter or dimmer than it thinks it should.

What mode do you have your camera in? Av, Tv, P, etc. I almost always use manual for flash photography, the only exception is where there's something dim in the background I want to capture.

[Hellashot]

test shots in manual exposure with FEC at +2

I was expecting it to act as my EX550 did and tell me I can use a faster shutter speed or can use a smaller appeture but it acted as if it didn't know it had FEC +2.

[tim]

Nope, it just makes the flash brighter or dimmer, it doesn't affect the shutter speed.

I'm no expert, but i've read a lot and i've played a lot. I suggest you try using M mode with settings F8.0 and 1/80th, and try changing the FEC on those settings. Then using FEC 0 alter the shutter speed and see what happens. Next keep the shutter speed constant and alter the aperture. You should learn some from that.

[Hellashot]

So basically there's no point in having in camera FEC unless you want to "shoot in the dark" and guess a setting that might work? I'd rather stick to my EX550 that actually works with the exposure meter.

[tim]

You can adjust the exposure on the 550EX or using FEC, it should make no difference. I have the same combination and I tend to do it on the flash myself.

[Hellashot]

What I'm saying is when I set FEC on my 550EX the exposure meter knows it and accounts for it. When I set FEC in camera the exposure meter doesn't know it was set.

[tim]

I'm sorry but you've gone past my level of knowledge, I think i'm just confusing matters. Lets hope someone else turns up and clarifies things :)

[Jon]

You told the camera you wanted FEC +2. You thus said wanted the flash to give +2 stops of light on the subject for the flash fill-in. Meanwhile, the camera's metering for a basic normal non-flash exposure when you're in M mode. Of course it'd be overexposed. Canon states in both the 20D and the Speedlite 550EX manuals that FEC set on the flash does just this. Please re-check the settings you're using and double-check that you're using M on the camera for both cases, and that aside from where you set FEC (on the camera or on the flash) all other conditions are exactly the same. Bear in mind also that Canon, in the 20D manual, states that FEC set on the flash overrides FEC set in-camera.

[Lenny_D]

My experience with the 20D , the 420EX and FEC is the following. Without FEC (or with FEC=0 as you wish) the unit works OK (both in Av or Tv modes) but tends to underexpose by 2/3 stop (can be seen by lookin at the histogram). When you change the the FEC to +2/3, everything stil works fine (in Av or Tv) but now the picture is correctly exposed. You can see that the histogram shifts to the right. I've been playing by changing FEC with steps of 1/3 stop (+ and -) and you can see in every picture that the histogram shifts accordingly.
So the camera just instructs the flash to give a little more light or a little less as specified by the FEC but it keeps the camera settings (time and diafragm) as calculated for FEC=0. So I guess that you can just leave the 550EX in automatic mode and the FEC will work as with the 420EX.