Aperture in Tv Mode

So I am currently at another family gathering tonight. I have to do a lot of handheld shooting and Av mode keeps on giving me slow shutter speeds, even though I am in very good lighting and using my 420ex flash.

I decided to switch to taking pictures in Tv mode and am getting very nice results. However, I am seeing that Tv mode keeps on giving me aperture values of f/2.8, regardless of the shutter speed . . . is that supposed to happen?

Thanks! I'm off to to take more pictures . . . Holiday time is giving me lots of practice.

Later,

In TV mode, the camera will pick a suitable aperture to get a correct exposure given your shutter speed. If your aperture blinks in the viewfinder when you take the shot, that means your shutter speed is too high and your photo will be underexposed, even at max aperture.

AV mode will meter for ambient light, that's why you get low shutter speeds.

The camera meter doesn't know or care that you have a flash attached. It will try to meter the ambient light. In P mode there is a floor of 1/60 sec, so it won't try to go slower then that. In Tv mode or Av mode, or M mode, the camera meter is showing you the correct exposure (for a scene that averages out to 18% grey). If your camera is consistently showing that you need the widest aperture for the lens you are using (2.8 ) it means that there still isn't enough ambient light using your settings to get a correct ambient light exposure. This is completely separate fom the flash exposure.

Scott

I've found (on the 300D) that, if you use Manual mode, the camera uses the flash as the primary lighting and exposes correctly. In Av or Tv it will attempt to meter using ambient light with the flash as fill-in. I believe this is detailed in the manual somewhere.

I normally use manual mode with the flash and set the aperture I would like then set the shutter speed around 1/100 or so then take a few test shots, check the histogram and adjust as needed.
The shutter speed won't make much odds here as the flash fire is quicker than the shutter speed anyway so anything fast enough not to catch movement after the flash has fired will be OK, then I adjust the flash power to get the correct exposure.

If you want to get a quick shot (with the flash) without messing around then use P mode

You are right. M mode(camera) is the only mode that doesn't invoke the infamous Auto Reduction of Fill Flash. Using M Mode helps keep the flash exposure more consistent and less often underexposed.

Happy Holiday
Scott