Anyhoo, after noting the above, i tweaked my process for my next batch of screencaps for this episode
, in widescreen.
My DVD player grabs the images at a "compressed" 750 width x 480 height, I kick it up to about 850 width without adjusting the height (as noted above). That leaves the proportions looking about right.
Then for the screencaps, I resized the width back to 350 with proportional width adjustment (putting the height at 197).
I did go ahead and sharpen them a bit. With IRFanView you just hit Shift-G and it does it in increments. I find that one increment gives the sharpness necessary. That, with the 350 width (I usually use 252 width), give me the detail necessary. At least on the monitors I'm seeing them on.
I didn't do anything with the lightness, but the DVD quality is pretty good.
I find the one-bump sharpness, at least on the color images, works pretty well, as seen here
. I'll have to see how it goes on the B&W TZ episodes the next time I do a few. They're already pretty sharp, though: must be the B&W.
So to answer the original question, you want a width-to-height ratio of approximately... .5647. If that make sense. So on a widescreen image take your width, multiply times .5647, and you'll get the right height. That means 624x352 sounds about right. Or 250x141. A 250x188 is indeed going to make your images taller and thus stretched upward.