I have a rebel 2000. I was looking at a particular indoor scene, and i raised the flash and set the values at 1/90 f/5.6 at 80mm in metered manual mode. The exposure meter showed underexposure as low as it could, i.e. 2 stops. However, when i switched to Program AE mode, the camera picked 1/90 f/5.6 (same as i had set) and obviously the little meter was dead center. Why is this? Does it have to do with the differences in metering between the two modes?

-- peter bg (pbg333@hotmail.com), May 22, 2001

Answers

You sure it didn't pick 1/60 and f/5.6 when in P mode? That's what it should have done. When in P mode and the flash on your camera should select 1/60 (if the light levels are low) and use the flash to provide proper exposure. P mode should only use 1/90 with a flash if the ambient lighting is bright.

When you use M, Tv or Av the camera assumes that you want a shutter and aperture that will give you a proper *ambient* light exposure and the flash will be used for fill only. f/5.6 @ 1/90 was obviously too low for a proper ambient exposure so it tells it's under exposing. You can ignore the warning and shoot anyway, but that will give the same results as the P mode (nearby subject properly exposed by flash and the background dark). But if you want the background to be properly exposed too, slow your shutter way down like the meter says and use the flash for fill on the nearby subject.

-- Jim Strutz (jimstrutz@juno.com), May 23, 2001.

Thanks for the reply. That is very good to know. By the way i just did the test again and it *definitely* is 1/90 f/5.6 in P mode.

-- peter bg (pbg333@hotmail.com), May 23, 2001.

Hey

I found the same problem: the camera giving the same setting in auto which it complained about when set manually. maybe it uses different metering schemes in the 2 cases. might be worth checking out.

-- Cruise (cruise125@hotmail.com), May 24, 2001.

As Jim S. alluded to, when using flash in P mode, the camera "assumes" that the flash will become the main source of light, IF the ambient light is low enough, but because it is in the PROGRAMMED or "P" mode, it will not allow a shutter speed below 1/60sec., as Canon figures this is the slowest shutter speed (with flash) that may render a sharp image with the camera being hand-held.

Try this: With your flash mounted on your camera (and the flash turned on), place the camera in P mode, and go outdoors on a reasonably bright day. (For the purposes of this experiment, do NOT set any exposure compensation). Next, focus and meter the camera on subjects in a variety of outdoor lighting, such as full light, as well as the light found in mild, medium, and deeper shade. While doing this, note the aperture and shutter speed solutions that the camera (in P mode, with the flash running) will display. You should see that when there is sufficient ambient light, the camera (in P mode, with flash) will often choose a shutter speed FASTER than 1/60sec., but it won't exceed the max. synchronized shutter speed of the camera. If the light is bright enough, the camera will also begin selecting a SMALLER aperture. By doing this, you can convince yourself that in P mode (with flash), the camera will only default to 1/60sec. when the ambient light is below a certain level. --> OK... Next, without changing any of your camera settings, take the camera and flash (in P mode) into a relatively dark room, and then focus/meter on something. (If you have an autofocus assist light, you can do this even in a totally dark room). What does the camera display as aperture and shutter speed solutions? It will likely display something like 1/60sec. at ~ f5.6. Here, the camera is "assuming" that the flash has become the main source of light, but regardless of the flash in use (as well as other variables such as film speed, distance to the target, and so on), there is no guarantee that the flash (with the camera in P mode) will be able to provide enough light for an adequate exposure, but the system will try to pull this off for you. But, the more powerful the flash (as well as whether or not the flash is "bounced"), the more likely that P mode will deliver an adequate exposure. If you're using a hotshoe flash with an exposure confirmation indicator, you can check this to see if the microprocessor "thinks" the exposure was good enough. Next, try the same thing in Av, Tv, or M mode, and you... well, you've already done this part of the experiment!

-- kurt heintzelman (heintzelman.1@osu.edu), May 27, 2001.