"Carlos E.R." wrote

| I was going to say that the camera with more megapixels would convert to
| a bigger size, but the reverse is happening.
|

MP doesn't matter because it's the same
number of pixels in the thumbnail if they're
both the same width/height. There could be
slight differences due to simpler or more complex
images that compress differently, but with such
a big difference the only explanation I can
think of is that there's a difference in the
compression. The code doesn't include a
"quality" parameter to set compression level
so maybe ImageMagick is deciding based on
input size? Who knows? He's using a hammer
to hit a tack.

It's hard to see why it should matter. He's
using a limited command line tool to get
thumbnails and not even setting the quality
option. Does he really need exactly that size?
If so, why? Is it worth sacrificing quality?
He didn't explain any of that. Apparently he
doesn't care very much about the quality but
is just curious about the different file sizes
resulting.