The garter snake shown above sat quietly while I shot about 15 photos, nudging the focus so it progressed from head to tail. The result is an image that has more depth but is not really sharp anywhere. So the answer to the question “Why not just stop down to say f/32 and increase the depth by four times?” is that while stopping down adds some depth in the out-of-focus parts, diffraction degrades in the in-focus parts. It is limiting, especially in close-up photography, at apertures that are routinely used in landscape photography. Diffraction is a quantum effect-if you limit where a photon has been you lose control of where it’s going to go. Squinching light through a small hole causes diffraction. To get a good image you need a wide bundle of rays, and wide bundles of rays need big complicated lenses. A lensless pinhole camera has enormous dof, but a very poor image. F/32 we don’t talk about.Īnother way of saying this is that there is a reason lens makers use all that glass. The are acceptable, but never their best at f/16. The lenses I use are typically sharpest somewhere between f/11 and f/4.5, and often in the low end of that range. Second, it forces you to use longer exposures, higher isos, or flash, all of which have drawbacks.Īnd third, and most important for the work I am doing, because it squinches all the light from the image down through a tiny aperture it degrades the image quality. If you are shooting a 36 cm rabbit facing you, it is only about a third of the rabbit. First of all, 12 cm dof of field still isn’t very much. The formula for depth of field is linear in the aperture, so going from f/8 to f/16 gets you to 6 cm of dof, and going to f/32 gets you to 12 cm. You can, of course, increase dof by increasing aperture. It is decent picture of a chipmunk, but a poor picture of the woodbine stems the chipmunk is sitting among. Add to this the strangely clumsy and problematic layout, which makes referencing during telescopic navigation of the Moon's surface less than straightforward.The image is cropped way down, the background is unimportant. There is also the classic Atlas of the Moon (Antonin Rukl: Kalmbach Books) while a masterpiece of cartography to be sure, there is something about these incredibly detailed drawings that does not translate ideally to our perceptions when we are scouring the lunar surface. Too bad a lunar observing authority has not yet compiled and printed a new atlas along Hatfield's lines. Times have changed, and advanced technology has certainly given us vastly improved methods of imaging the Moon. Surprisingly, there are few really first-rate choices for the amateur observer available, although Hatfield's Lunar Atlas (a veritable classic dating from the 1960s and now reprinted by Springer) probably comes closer to the mark than most, despite its old, somewhat obsolete photographic imagery. It is certainly one of the best, if not indeed the best of its kind for the amateur observer, containing in its numerous pages highly illuminating, imaginative, and detailed methods to view and study the Moon's surface. Of the many printed resources available for the amateur observer, there is the excellent book Observing the Moon (Gerald North: Cambridge University Press, 2000) an outstanding reference volume by a tried and true lunar observer. Because so much excellent material about the Moon is widely available, this book does not intend to parade a restatement of now familiar themes and information, already superbly laid out by some prolific lunar authorities.
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