[PLUG] Strange Image Magick issue

[Matt Alexander]

I'm trying to make an image 50% of it's original size and convert it from
TIFF to PNG.

When I use convert without any options, I get the following:
convert image.tiff image.png

117K image.tiff
206K image.png

I'm not sure why PNG is so much larger, but whatever...
Here's the odd part:

convert -resize 50% image.tiff image-50.png

654K image-50.png

The image looks 50% smaller when I open it, but why did the file size
balloon?  And what do I need to do to make it a smaller file size?
Thanks,
~M