As Dom mentions above, the camera’s light meter will try to go for “18% grey” (I understand this to mean halfway between black and white by luminance). This is very helpful, and is a sensible sort of thing to do, but doesn’t always lead to the best photograph.
It isn’t a fault with your camera, or with your photography – if you know you like shots that are one stop down from the camera’s light meter, use the exposure compensation setting and you’ll be set. Don’t be afraid to try photos that are further away though, sometimes you can get much more evocative images this way.

long exposure speed will also result in noise, the correct way is to balance out everything to your satisfaction criteria.

I Only recently realized what those bars with numbers were on my camera, (i am very new to photographie). Since i found out that this was metering, i started playing around with it and found it to be very effective way to get my shots right the first time since i shoot in manual mode and constantly play with all my settings.
one thing i found is i always have to get my exposure on the camera metering one stop lower than recomendation to get the exposure to my liking, Why is it this way? I have a Canon XS camera.

I think a bunch of discussion on the scenarios is ok – that’s what comments are for…

I agree with Alex’s comment, being a fellow strobist, on how to set up off camera flash. The one part I don’t agree with is letting the camera figure out the correct exposure.

I don’t agree with Eric’s subsequent comment regarding keeping the subjects still. If the shutter speed is slow, but reasonable, say faster than 1 sec, the flash will freeze them appropriately even if they twitch. That is due to the speed of the flash which is way faster than the shutter speed (~1/8000 of a sec or faster).

He is absolutely correct that you can control your exposure to your advantage by changing the ISO. However as rightly pointed out if the camera is in auto mode it will simply shoot the equivalent exposure. The only way to correct this in aperture or shutter priority is to change the exposure compensation. But to show an example of how changing the ISO can be used to get the desired picture results:

Picture this real example from when I used to photograph motor sports; you want a shutter speed of 1/500s and you also want to shoot wide open to blur the background and get separation of your subject. Assuming you have to correct exposure compensation to get the right exposure, you set your camera to 1/500s shutter shutter priority. You then reduce your ISO enough so that you’re shooting around f/2.8 – f/4. If it’s really bright sun light you won’t be able to get that wide but you go as wide as possible. As the light levels drop you will eventually find that the camera starts to underexpose because the shutter speed is fixed and the lens is as wide open as it will go. You can now correct the situation by increasing the ISO a stop or two so the camera is able to produce correct exposures within the set parameters. This is the effect that I believe Neil was referring to. It is all about taking control of your camera to produce the effects that you desire.

What Neil does not mention here is that this is a reflected meter reading and not incidence, so the meter will be fooled when measuring dark or light scenes. This is because it will always average the scene to 18% grey. Probably too advanced for this article but if you want to do further reading check out zone metering for digital photography.

Another point of note is that your camera meter probably under exposes between 1/2 to 1 stop. Once you have tested your camera you can compensate for this. For example my Canon 1Ds and 10D under expose by 2/3 stop while my newer 5D only underexposes by 1/3 stop. See how accurate your camera exposure is.

Pat Bloomfield
Suffolk Wedding Photography