I wouldn't trust just using the camcorder for recording the sound while recording picture. Recording the sound from the dedicated solid-state recorder as a Primary should also be performed. You never know when you are going to have some kind of glitch or drop out? And with lectures, you don't want to miss a word. Coming from a network television background, we always practice redundancy. So that's also where that secondary camera shot would be utilized and the soundtrack from your solid-state recorder.
Zooming in and zooming out is also Obnoxious to look at and wreaks of amateur hour. That's where that cutaway camera comes in. You switch to the cutaway camera when you are zooming your primary camera. Then you go back to your primary camera with the newly framed shot. You may also need it if there are any screen projections. Then you go to the cutaway camera while framing your main camera again for the screenshot, blackboard, whiteboard, computer displays. Panning and tilting a camera on a tripod without a "fluid head" is 10 times more of noxious looking. And that's why you want that secondary shot that's locked down generally. You might even want that shot to not include a view of their lips? That way, you can use the cutaway whenever necessary with or without synchronization. Since you have already indicated you're going to do some postproduction in your computer, this is the way to go. You want to be a professional and this is the way professionals do it. You don't want to use your main shot camera as a cutaway due to a video glitch since there will be no lip sync. And that secondary cutaway camera could be just about anything since you're only going to go to that shot just for a couple of seconds. You'll also be able to get away with a far more affordable main camera if you're not worrying about trying to get quality audio Into or,out of a common consumer camcorder or even a cell phone. That's a lot of cabling and a pain in the butt. Otherwise it could get so poopie looking & sounding, that you'll destroy your reputation as a professional. This can be a good source of income for you so don't screw it up.
The solid-state recorder can even make your life so much more easier. You could even simply drop it into their breast pocket and if it's small enough, even in a woman's brassiere (guide her as to where to place it. Don't do it yourself unless she wants you to. Then you may also have to take her out to dinner later?) You might also want to purchase an inexpensive lavalier/tie tack microphone to plug into the solid-state recorder. Then the solid-state recorder can simply be placed in any pocket. Make sure your solid-state recorder is set to ".wav" and not MP3. You also want to set to 48 kHz sample rate. 16-bit is perfectly fine, perfectly common and easy to utilize in most any program. Also, with spoken word, if you're going to do some postproduction in your computer, it would also be a good idea to include some limiting to smooth out the lecturers voice. And before long, people are going to ask you to start doing all sorts of other video work. So whether it's just a lecture or not, you want to put your best foot forward. Keep your cabling and set up to a minimum. You're at the back and there at the front which means you'll be taping down cabling all the way back to you. Why bother if you don't have to? So, let's review... crappy consumer camera in the front. Crappy consumer camera on the side. Simple solid-state recorder in their pocket eh voilą!
If possible, you may also want to place the camera into manual focus and/or manual exposure control. The focus can be confused quite easily by somebody in the front row getting up to move and stuff like that. Automatic exposure settings can wash out bright items such as a large sheet of paper they may be drawing a diagram upon making it unviewable. You can also set your automatic exposure to tell it to cheat the aperture down .5 to 1 full smaller aperture to keep the whites at 80% instead of 100% video. That's what I do. Because once you've had 100% video, nothing is recoverable from that. It's the visual equivalent to pure audio distortion which I think is an oxymoron? There is nothing pure about distortion when it's distorted. It's easier in software to increase the brightness if necessary and really not effective when you're trying to lower the brightness level because detail has already been lost. Also remember when shooting female lecturers, you might get arrested? The same holds true for shooting male lecturers. So just run the camera, please. No shooting.
Mx. Remy Ann David