Could someone explain how FEL works on my 400D

1. FEL locks the exposure of a certain part of the picture that you want exposed properly by the flash if it is not central...very much like normal exposure lock.

2. The background/ambient light is controlled by the shutter speed and the subject is controlled by the aperture and the flash.

If you use program mode it will automatically set the shutter speed to 1/60th and the background will have a certain amount of light but not a lot.

If you use faster than that it will be all black as it is not open long enough to capture the background light.

If you use a slow shutter speed you will have the subject exposed right by the aperture and flash settings and the background will have ambient light in becasue the shutter is open long enough to let it in, although you may have to use a tripod unless you are happy with slighty blurry background like in a club or something.

Hope that helps
 
Thanks but I cant figure it out, maybe im not having a good day. I am using an external flash its not much good but does have ettl and so on.
Well I shot once at 1/60 f4 and once at 1/200 f4. Both shots look almost exactly the same. I focused on the white bar but the light in the corridor behind is still very easy to see. I dont see how it would be black anyway.

1/60 f4
60.jpg



1/200 f4
200.jpg
 
I think its more a case of if the background is dark already.
You wont be able to make a background darker than it is already... but you can make it lighter by letting more light in.

Also it means further away than in your picture....... like at a party or something.. not a few feet behind as that will be catching the light from your flash.
 
Ahh I see. I did once read something where you can take a picture of someone during the daylight and have the background dark.
Since its night here I can test but would you have a fast shutter (1/200)?

Also, for some reason, if im taking pictures now in the semi darkish room i am always at f4 and below, the lowest my lens will take. Even if I use the FEL button, this number never changes. Am I missing something?
 
To have the background stay dark you simply need to ensure that there is a lot less light on it than the subject. The most obvious example would be to have someone stand in bright sunlight but in front of a shaded area such as a dark bush which is exactly the situation here:

web_4903.jpg


Bring flash into the equation means you're putting more light onto the subject and increase the difference between the exposure for subject and background. You might want to do this in a situation where the background isn't dark enough, by adding more light from the flash and exposing for that you are effectively under-exposing the background even more until, eventually, it will be black.

The key here is to think of the background exposure and subject exposures as two different things - find out what settings you need for the background to be black and then get enough light on the subject for those settings so they are correctly exposed and job done.
 
Starting to make a little sense but wouldnt the light from the flash pick up whatever was behind the cat?
 
Depends how far away the background is, just make sure it's enough for the flash burst to fall off by the time it hits it - as a rough guide if the background it 4 times the distance of the subject you'll be fine.
 
For a dark background with flash you have to use manual mode not Av or Tv - otherwise the camera will be taking an available light shot and the flash just providing fill.
 
So on a normal day you would need the max shutter speed and a very high f number in order to gt the background black. Then hopefully the flash will pick out the subject.
 
Pretty much yes but you can help improve the situation by choosing a background that's dark and/or in shade.
 
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