I'll take a crack at explaining how I'd do the translucent thingy in Photoshop. Sorry it's a little lengthy, but hopefully it makes perfect sense...
-Choose white as your foreground color.
-Draw a circle around the enlarged "inset" portion of your image, using the ellipse shape tool (not to be confused with the marquee tool. Hold down shift key to constrain to a circle). A new layer will appear in the Layers window that looks like a masked layer.
-Duplicate the circle layer in the Layers window.
-Scale down the duplicate circle, and drag it over to the area of your image that the inset depicts.
-Duplicate both the small and large circle layers.
-For each of these two new layers, double-click on the "mask" side in the Layers window. In the window that comes up, check "stroke" under Styles, and change the opacity to zero under Advanced Blending.
-In the Layers window, drag the new layers (that now show outlined circles) to the top.
-In the Layers window, click once on the smaller white circle layer to select it.
-Using the pen tool, draw a white-filled polygon connecting the two circles by clicking on tangent points on the circles. A new layer will be made.
-Hide all the layers except for the small white circle and the polygon, then choose Merge Visible in the Layers window options.
-Show all layers, then select the "mask" side of the large white circle layer.
-Go to the Paths window, and in the Paths options, choose "make selection."
-Go back to the Layers window. Click once on the merged polygon-circle layer. Hit the delete key.
-Adjust the opacity of the merged polygon-circle layer to the desired level.
You should end up with something like this:
