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Whenever I am taking a picture on macro near the maximum close-up to an object, the aperture on my little Canon automatically sets to the maximum size, which means that the resulting images are in focus only at the center. Ever since I got the camera in late 2008, I've wondered how to get past this problem. In flash mode, the aperture decreases, extending the area of focus, but the image gets overexposed. Yesterday morning, I finally hit upon the (obvious) solution: set the camera to flash mode, but block the flash with aluminum foil. I had thought before that the result would be too dark, but with some white hoar in the picture, the image is bright enough. (Later I found that the image is fine, though a bit dark, even without hoar.) For a reason I don't understand, the exposure time is still relatively long with the flash on and the ISO value set low, so I probably need to better stabilize my little makeshift wooden 'tripod' and set a longer delay to allow vibrations enough time to damp out. Even so, the improvement gives me more room to explore in the miniature world of frost, which I call 'frost world'. For example, the image below, taken on the roof of a black car yesterday, shows some pyramid structures sticking up, a few valleys, straight ruts, straight streets, and parallel curving streets. The basic structure was laid down when the film of condensed water froze, which I call "film frost" (though it has no standard name) and then later hoar crystals grew up off the surface, adding a little white to the landscape. In this image, nearly all of the hoar is hexagonal.
However, when I enlarged the images, I saw that the focus was pretty good. The fuzzy effect seemed to be coming from the crystals, perhaps because they were relatively large and had interior parallel lines. The fact that the crystals were a lot brighter than the leaf may have increased the effect. This brightness makes the crystals seem to float above the leaf. Notice also that the hexagons are all nearly alligned, by which I mean that their sides are all nearly parallel. This indicates that the hoar grew off film frost.
I've noticed that leaves often often have brighter hoar, due either to a higher density of crystals or larger-sized crystals, on veins that stick out. The above leaf doesn't show this effect because the veins don't stick out, and I've seen leaves that instead had the reverse effect (less hoar along veins), but the leaf in the image below shows the vein-highlight effect rather well.
Even though the veins stuck out, they still seemed to have had film frost. For evidence, notice how the crystals along a vein are nearly aligned (below).
To make this easier to see, I marked some crystal sides in the image below. Some I marked red, some I marked green. The red outlines are all along one vein and are all nearly parallel, similarly for the green outlines on a neighboring vein. But the green are roated from the red.
The film that I think was on the leaf probably started to freeze from one spot and then spread over the entire leaf surface. But strange things happen when a film freezes, including gradual rotations of the crystal orientation and sudden changes in orientation.