Phil Davis wrote:
I'm inclined to use a longer lens since it is more flattering, and shooting vertically.

A couple comments about this. First, longer lenses are not more flattering in and of themselves. The only thing that matters when it comes to perspective/facial distortion is the distance between the camera and the subject. The further you are away, the more compression you'll get. Of course a longer lens will allow you to fill the frame from further away, but the actual compression of features happens because of the distance, not the lens. Every rectilinear lens will give exactly the same perspective/flattening of facial features if you use them all from the same distance away.

I bring this up because it's a common misconception and has some bearing on your proposed photo sessions. If you're getting full body shots, you're going to have to stand far enough back that you'll get a flattering perspective even with a 35 or 50mm lens. On a 20D with the crop factor, you're going to be even further back; you could probably use a 24 or 28 mm lens for full body shots and still get pleasing facial perspective. There really is little point in standing 30 feet away from your subjects just so you can get their entire bodies into the frame with a long lens. Use a shorter lens, stand 8-12 feet away, and be confident that you're far enough away for a flattering perspective.

There will be activity around me so I have to be mindful of interference.

All the more reason not to put so much distance between you and your photographic subjects.

However, if there is rain, the alternate is the reception room in the press box, a much smaller space, bad flourescent lighting, dfn CWB stuff.

Consider shooting RAW and adjusting white balance in post processing if you have lighting like this.

I think I should be more specific about "portrait". These are not head shots or even waist high shots. These will be full body shots which almost certainly will include some clever signs/banners conceived by the students.

If the banners are over their heads or particularly wide, then you'll have to stand back even further. A 70-200 on a crop body makes little sense. If the lens list in your signature block is complete, I'm going to have to suggest using the kit lens. Alternately, consider picking up a 28/2.8, 35/2.0, 17-55/2.8 or 24-xxx zoom before the job.

Good luck.

If the lens list in your signature block is complete

I could revert to film where I have a ton of lenses, and som every fast ones, but that means scanning, etc. I do have a 120-300mm/f2.8 but that wold be even harder to use. I think what I'll do is borrow a couple of lenses, plus my own, and go over this weekend and see what works best.

Planning! The key to success. It's surprising how many people go into jobs without taking the time to test things out, learn what works, etc. Bring an "assistant" (child, wife, friend who owes you money, etc) with you to act as a model. Try various focal lengths and distances from your subject to see what offers you the facial compression you desire and a suitable background. Shoot also at a variety of apertures to see what kind of DOF will be required. If the sun is particularly bright, remember that people will tend to squint if it's in their field of vision, and will have harsh shadows in their eye sockets/under their noses and chins, etc. Pray for bright overcast conditions -- the photographer's best friend. No squinting and flattering, diffuse lighting!

The 85mm 1.8 is a lovely little lens, but might be a tiny bit long for your general usage.

If you really want the lens for your purpose (and on 1.6 crop) it is clearly the 24-70 2.8L, which is versatile, fastish and supremely sharp

However it isn't cheap. But it does cover 24,35,50 and 70mm

David

If you like longer lenses for shooting portraits, I'd go for the 135 f/2L....I've shot with it once, and the images are magic....plus it's pretty cheap (it's all relative) considering the incredible image quality. I think it is neck and neck with the 85L for best portrait prime.

Were you shooting with FF or a cropped sensor?