Best lens for a group shot of 200

I have been asked to do 2 separate shoots of 100-200 people in a grand stand setting. I do not own a wide angle lens and want to purchase something cheapish, second hand. I have been looking at the canon 17-80mm but am really uncertain! Obviously I would like to increase the amount of lenses I have but funds are tight and I do not want to end up with equipment I don't use. I primarily do portraits and weddings. I would like a nice wide angle to have also as I would like to do more landscapes through out my training. Any help would be much appreciated, Thanks!

Use what you have now.

That question isn't really answerable without knowing the location or your current gear.

Longer lens+back up = less distortion on the people.

Wide angle shots might make shooting the group easier as you can be closer, but as mentioned, a longer lens will lessen the distortion of the people at the edges. Downside is that you of course have to be farther away. But list out what you have.

Since you say you're already a portrait and wedding photographer I'm a little surprised you don't know this already, but a really wide angle lens is a bad choice for taking a group portrait of 100-200 people. It would be impossible to capture the correct perspective across the photograph.

To shoot a group this large and ensure that the group is recognizable, you can do one of two things:

1) shoot a panorama in the neighborhood of the 50mm range
2) use a longer focal length and shoot from much further back, and from a higher angle...a very tall ladder or boom would be very useful

I'm sure others can offer additional advice, but these are two general ways to do it.

Bryan

A standard zoom would be best. If you use a wide angle and stand close the people in the front will be larger than the people in the back. Use around 50mm, and you may need to be up on a ladder or cherry picker. Use whatever ISO is required, make sure you have at least F5.6 and 1/100th.