Yesterday morning was minus 23 degrees at my office, and about noon, when the sun rose over the distant mountains and cast its glow, I was struck by the light on the window frost formations. The near perpendicular angle of the sun is the cause for the amazing separation and differentiation between the crystal shapes. A little blue from the sky and a little yellow from the sun add pleasing tones to the image. This was the last frame in a series shot with the 100mm f2.8 macro in which I added a 25mm extension tube to allow a tighter composition. This specific lens has a flat-field design which is optimized for edge-to-edge sharpness of flat subjects. One needs to be very careful however to be exactly perpendicular to the subject, since depth of field becomes extremely minimal under high magnification photography. The second image reveals detail by zooming in on the frame.