This might be tough using words instead of pictures but I will give it a try.
The first problem is that no matter how you scale up the text, it will not be all that sharp. Not unless you start off with the text beling larger and scale it down to fit the video frame. In that case you can zoom back up to 100% without a problem.
Second, assuming you have nice clean text at the size you want, you could have a second copy of each line of text on a higher track that you can then zoom up to 100% individually. You could use the crop effect to isolate the line or lines of text. When you do this properly with keyframes, it will look like it is popping off of the screen, especially if you dim the background a bit and add a drop shadow to the zoomed in text section.
All of this depends on just how much larger you want the text to be. If it gets too large you will need to word wrap and that gets more complicated during capture. If just a litle larger, then perhaps you could zoom up to 150% without having it look too bad. It depends on the font pretty much. Straight lines are more easily zoomed in than curves.
I will play with this a bit and see if I can make a quick tutorial that demonstrates the concept as I see it.
Well, it turns out I was wrong. I can easily go up to 140% without a problem.
Here is a video showing one possiblility. I did in 12 seconds what you would probably do in 30, but you should get the general idea.
I used a static picture of the screen, and stuck a photo in the corner to represent a webcam image. All I did was put another copy of the text on the timeline for each section I wanted to enlarge. I used the crop effect to isolate the text. (Actually a third party feathered crop but I ended up not feathering it after all.) I then turned the opacity of the copy down to 0% until I needed it at 100% by using hold keyframes so that it would pop up all at once instead of gradually.
Then I used keyframes on the Brightness & Contrast control to gradually dim the background over 15 frames.
I then scaled up the text to 140% and repositioned it to the center. After a short time to read the text I returned it to its rightful place and one frame later I set the opacity back to 0%.
I repeated this with the second copy.
If I gave it a little more thought I might have played with the levels to darken the enlarged text a bit. But I will leave that little bit for you to try.
It took longer to figure out what I wanted to do than to actually do it.
The timeline looks like this.
Thank you thank you thank you!!
That was it, your 12 second video is exactly what I was going for. What I was missing before was the 'crop' effect. I got a bit confused becaues 'crop' kept me thinking about cropping the video from the timeline/sequence and no 'crop' from the actual picture itself.
Anyway, after applying the crop effect to my video 2 (I just clipped a section and put it 'above' the first video in the timeline) and then resizing, etc it works just like I wanted to.
The quality of the text is good, I recorded in1080p and even when zoomed at 190% it's still very clear.
Anyway, thank you very much for your help, it is MUCH appreciated!
It was rather entertaining figuring it out. Besides photography and making videos, my hobby is figuring out ho to do things. I didn't really know for sure until I tried it myself. You never know when I might this myself.
Funny thing that I'm not too embarrassed to admit. I originally ran across the crop effect a while back, but didn't realize it was the right tool. This is because I had the full video, plus a copy of a clip right above it (overlaying on top of it). When I used the 'crop' effect I didn't notice it actually cropping anything. This is because the both video layers were of the exact same image, so while I was resizing the 'top' crop, it was still showing the background video, giving the illusion that I wasn't actually cropping anything.
Rookie mistake, but at least with your help I got it all figured out now.