Here is a question related to physics (optics to be precise). And in order to fit into the season it comes in a nice holiday wrapping... The story starts with a christmas tree (with LED lights) which I set up on our balcony. Being bored one evening I remembered my early photography days (around 2009) when I first got the Pana 20mm and made a custom star shaped aperture for it. So I dug in our tinker box and came up with a reindeer puncher. With that puncher I made a custom aperture in form of that reindeer (for the Oly 45mm f1.8): With that I photographed the lights of our christmas tree yesterday evening. The "trick" is to have the lights out of focus so the lights are blurred and take the shape of the aperture (usually round but with the custom aperture reindeer shaped). Here are two pictures - the first with focus set roughly between the camera and the tree and the second with close focus on the lens. Ok, so far for the "background story". Lets come to the question. When I pixel-peeped on the reindeers I came across very interesting effects. There are at least three effects I didn't expect (at least not without having spend any thought on it so far). A brighter border around the reindeers "Ripple" effects inside the reindeers towards the border "Rays" around the reindeers (best seen on the first close-up - looks almost like fur) Here are close-ups (100% crops) of the two pictures. There you have it. My guess for the ripples is that is has something to do with refraction and the "rays/fur" with the paper/cardboard used for the custom aperture. But any proper explanation or insides on this would be very nice. Nice holiday season by the way.