Information
Purpose: Compare "16:9 to 4:3" and "4:3 to 16:9" conversions
Movie: Men In Black 2
Editing done in: VirtualDub
Original Picture

[640 x 352]
16:9 to 4:3
1. Original Size DVDRip ScreenShot (640 x 352)

2. Method 1: Crop Sides (470 x 352)

*I admit that cropping sides doesn't look all that bad, but this is the best screenshot I could find that proves that cropping is bad.*
3. Method 2: Stretch Vertically (640 x 480)

*This doesn't look so bad since the aliens are tall and thin anyway, but there the humans look really, really bad.*
4:3 to 16:9
1. "Original" Size DVDRip ScreenShot (470 x 352)

*This is just a hypothetical 4:3 of the movie, since I don't have it in 4:3. I made this using Method 1 above.*
2. Method 1: Crop Top and Bottom (470 x 260)

*This is a cropped version of the one above, but I didn't upscale it to keep the quality.*
3. Method 2: Stretch Horizontally (640 x 352)

Verdict: Just don't even do it, because you'll either lose some picture, or it'll looked stretched.