Here are some of my concepts. I've gone for something that's fairly clean and simple, yet striking. Creating an icon that works well within the logo or as a stand alone element, one that can be used for things like favicons or watermarks.
The logos are 100% vector so will scale well to any size, and works well in full colour, B&W and on coloured backgrounds if needed,
It would be my pleasure to work up any variations so please do say. I look forward to your comments or thoughts.
My idea was that the circle that goes over the "DM" represents a lens (in its simplest form). But what I've done is changed it slightly so its a stronger representation ... hope that makes sense :)
A few variations ... I also tried to include the Golden Ratio, so with #198, the rectangle is at that specific ratio where one side divided by the other (a/b) = 1.61. Which is similar to the National Geographic rectangle.