Low lit conditions - background very dark - user error or my flash?

I'm new to digital SLRs and need some advice to point me in the right direction.

Using a Canon EOS-20D and a 420EX Speedlite if I take a photo of a group of people in a low lit situation like a bar or club the people in the foreground are exposed correctly but the background (and any people in the crowd behind the main subjects) is pretty much dark and sometime black depending on the amount of light at the time.

Previously I used a point and shoot digital camera and when taking these shots I had a well lit / vibrant background. on my digital SLR Is this user error caused by myself or is it a case that my 420EX Speedlite just isn't stong enough for the situation I'm photographing in?

Posting two images with EXIF information (from the 20D and from your P&S) might really help us here to give you a meaningful answer.

Other than that, I'd also expect for the situation you describe that the front is well lit and the background is dark.
To get the background bright as well, you have to increase shutter speed, ISO and aperture.

If you can't post images, just post the EXIF info (shutter speed, aperture, ISO, metering mode) as text.

Best regards,
Andy

This is a normal phenomenon with direct flash in a dark environment.

The amount of illumination from any light source falls off exponentially. The amount of light 10 feet away will be only 1/4 as much as the amount of light 5 feet away from the light source. So the brightness of people in the background will depend on their distance from the flash, relative to the subject.

The E-TTL II flash metering system of the 20D will attempt to properly illuminate your subject. Less expensive P&S cameras would meter to average the scene, making the background brighter but often overexposing the subject.

If you have a white ceiling that's not too high, bouncing the flash will help spread out the light and even things out somewhat.

What mode is the camera in? if you set it to Av, it'll try to expose the background properly (at risk of a long exposure) while the flash lights up the main subject. At other settings, the background won't get enough light unless it's really bright there.

As Jon points out, the mode you shoot in plays a very important role in the outcome. Other factors (e.g., ISO) are also at play. The following article will explain all you'll need to know on the Canon flash system:
http://photonotes.org/​articles/eos-flash/

and ill second Curtis about bouncing the flash off the ceiling.
I have the same flash gun and alwas bounce the flash. makes such a difference.
Also if you set the flash to hi speed mode and use TV you can go above 1/60th second at higher iso settings. the camera will tell you its under exposed but ignor it and just shoot. i have had great shots at 1/160 sec. raw will also help here.

Dave.

if light falls off exponentially:
Given that the amount of light 10 feet away will be only 1/4 as much as the amount of light 5 feet away from the light source.
At 15 feet the amount of light would be 1/16.
At 20 feet the amount of light would be 1/64.

however, light actually falls off as inverse square:
The amount of light 10 feet away will be only 1/4 as much as the amount of light 5 feet away from the light source.
At 15 feet the amount of light would be 1/9.
At 20 feet the amount of light would be 1/16.

When using a single flash set up as with a single on camera flash, think:
1. Subject - flash illumination
2. Background - Ambient light exposure Aperture + Shutter speed.
To brighten your background you need to use your camera's ambient exposure, as in slowing the shutter or opening the aperture to more properly expose the background. This usually requires a tripod and asking your subjects to remain still after the flash until the shutter closes. This is called "dragging the shutter", "slow sync flash", or "Night Portrait".

Flash pictures are a combination of the exposure from the flash and the ambient lighting.

One way to brighten up your backgrounds indoors is to put your Flash in Manual Mode, and place some small inexpensive battery powered Slaves in a couple of corners of the room or behind a couch or chair. It won't work in ETTL/2 due to the preflash setting off the slaves.

My use of the term "exponentially" was perhaps a bit vague. I understand the concept but didn't explain it properly. Thanks for the clarification.

I believe Andy meant *decrease* shutter speed(?).

Anyway, flash photography 101. Shutter speed dictates how much *ambient* light is let in. Aperture dictates how well the *subject* is exposed. If you think about how light works, the light comes from your flash, goes to the subject, bounces off and comes back into your sensor. It doesn't matter if your shutter is 30seconds or 1/100th, the same (approx) amount of light will come back.

In Av, you can meter for the background and use the flash to expose the foreground. There is *so* much on flash photography out there, it's really learning photography all over again ahahha.

I <3 available lighting.

You are absolutely right
I meant shutter time (how long your shutter stays open), shutter speed is the exact opposite.

But judging by the lack of EXIF information posted so far (about 2 minutes work), the problem is not that pressing

Best regards,
Andy

I agree with dragging the shutter. Makes interesting pictures.

At least sombody read my post.