create perfectly cropped thumbnails of varied sizes

Hi Guys

I have been trying for quite some time to create a number of different sized thuumbnails to use on different pages in my blog. I have used some code like this in the functions.php:

add_image_size( ‘author-thumbnail’, 60, 60, true );

And from the research I have done online it seems to be the best way to go about achieving a cropped thumbnail rather than a resized thumbnail. But it seems when I set the values for example to 60×60 is just resizes the image and doesn’t crop it but if the value is 210×210 it’s crops the image.

I’m not usre if I’m understanding this wrong and if I should be taking a different approach but I can’t seem to get this to work.

I would like to create a small thmbnail to use on my archives page and I would like all the images to be exactly the same size otherwise the layout looks a little strange.

I am developing locally therefore unable to share a URL, I am also using a child theme of twenty ten.

Thanks in advance to anyone that can help.

=)