kenrockwel对D信息是这样描述的： （转载自 http://kenrockwell.com/）AF-D; "D Type," 1995 Another very subtle improvement you may safely ignore. These lenses let the camera know the distance at which the lens is focused. In very rare instances it helps the matrix meter, especially with flash, determine the exposure more accurately. The biggest difference with D lenses is using flash and with subjects occupying only a small part of the frame. THe distance information lets the newest cameras get the correct flash exposure, while with non-D lenses the camera has to guess harder. AF-D work the same as AF lenses, even in difficult flash situations. The only difference I could see was if I had a backlit shot with an object in the foreground. If you focus on the foreground the image attempts to expose the flash for the foreground object, and if you focus on the background, the foreground object becomes too light
Another improvement is if you want to photograph straight into mirrors. Without a D lens you'll get underexposure because the image of the flash in the mirror fools the meter into underexposure. With D lenses you'll get a properly exposed image of a bright flash. I've expended film on this foolishness so you don't have to.If you are buying used lenses on a budget you can get the earlier non-D versions cheaper. Don't worry here. In fact, the instruction manual of the 105mm f/2.8D AF Micro-Nikkor cautions that the D feature of the lens can lead to the WRONG EXPOSURE unless you keep your flashes at the same distance from the subject as the film, which is a real obstacle to creativity. There are a couple of ways to signify a "D" lens: Nikon usually marks its lenses as "50mm f/1.4D AF" as opposed to "50mm f/1.4 AF-D," but it all means the same thing. Most AF-D lenses are AF and AI-s, and work great on manual focus cameras. You'll need to have a coupling prong added for use with the meter on ancient pre-AI cameras. THe D feature has no direct relation to autofocus speed, however as Nikon introduced newer D versions of existing lenses they sometimes sped up the autofocus speed, too. THe Nikon 70-210mm f/4-5.6 is an example of this; the D version focuses several times faster than the earlier one. The speed comes from a change in mechanical gearing inside the lens; not the D feature itself. Focusing speed has nothing to do with whether or not a lens is D. Of course newer lenses are D and newer lenses tend to focus more quickly, but the focus speed is determined by the gearing between the AF coupler and the focus ring, not the D feature alone. All the newest AF lenses, even AF-S and especially G, are also D. Nikon doesn't bother to mark it anymore.
[ 此帖由 猫咪熊 最后编辑于: 2008-03-10 20:31 ]
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缓缓，缓缓
为什么叫很奇怪的名字？
因为猫可以无时无刻的睡觉，而熊可以冬眠。。。
体重又增加了。。。超郁闷。。。
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