How to remove the background of selected area

[kevinjc1]

Hi.

I'm trying to convert the NSF logo from NSF official website to a .png file with transparent background.
Here is what I have tried,

convert nsf1.tif nsf1.png
convert nsf1.png -transparent white nsf1-transparent.png

The result is the background along with the 'NSF' letters are transparent, since those 3 letters are also white.
I'm wonder how can I preserve the 'NSF' letters' color from being convert into transparent.

I know there is plenty of this logo with my specification online, but I just want to know how to solve it in ImageMagick.
Here is the resource
https://www.nsf.gov/policies/logos.jsp

Thanks a lot!

[fmw42]

Please post the exact logo version from the website that you are trying to use. Is it with or without shading? You can post to some free hosting service such as dropbox.com (be sure to make it shareable) and put the URL here.