I wanted to use Enhancer to create circle images on a responsive website, but shape changes as viewport changes. Smaller=greater radius. Is it possible to make the shape consistent on all viewing platforms.

My url is: dm-webcreation.com/airpyramid/

Please be a little more detailed? What exactly is the border radius set and where did you set it?

Border radius set at "50" for all four corners. Setting made in Image Enhancer Control Panel. This setting was applied to the three images at the bottom of a modified Bootstrap 3 Landing Page Template.
URL: dm-webcreation.com/airpyramid/

I have only set the radius parameters once in this webpage, yet When viewed on the iPhone sized viewport, the corners of the image increase too much.

Hello David,
The border radius is actually not increasing.. it is always 50px. It is your images that get smaller, as they are responsive.

Is it possible to use a percentage rather than a specific px size? Or if I wanted circles could I use Bootstrap3 "img-circle" and remove radius from Image Enhancer?

Yes, you can use percents as values.