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發表於 2007-7-24 21:41
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剛剛在對岸網站查到資料，這問題好像是EOS 3常發生的問題。
也就是說EOS 3的對焦屏很容易偏移。
A Problem With Off Centered Focusing Points?
It was reported that a small number of early production Eos 3 models did not project the focusing points where they should be onto the screen. In some models, the points were reported to be slightly off center either to the right or left by about a millimetre or so. The problem is not with the focusing point projection mechanism but the positioning of the focusing screen. If you find your Eos 3 does not have a perfectly centered screen, don\'t worry, the camera is not faulty and it can be easily remedied. Chuck Westfall of Canon USA\'s Camera Division gave an explanation in the Compuserve Forum.
\"The position of the mechanism that projects the outline of the EOS-3\'s 45 AF frames is fixed and separate from the focusing screen. (The projector is above the screen and at right angles to it.) Because the mechanism is essentially locked in place, it\'s possible to ensure that it\'s perfectly centered and aligned with the position of the actual focusing points themselves, which are located on a CMOS chip in the base of the camera\'s mirror chamber.
\"On the other hand, EOS-3 focusing screens are designed to be user-interchangeable parts. Every effort has been made to ensure that the frame holding the screen positions it precisely and consistently in the geometric equivalent of the focal plane, no matter how many times the screen is exchanged. However, to make it easier to exchange the screen, Canon Inc. allows a very slight tolerance (approximately 0.3 to 0.5mm) in the left-right positioning of the screen, even during initial installation at the factory. It has absolutely nothing to do with shock or shipping. The fact that users are able to make a slight adjustment to the left-right positioning of the screen is a by-product of the camera\'s design. Ultimately, it\'s no big deal,\" said Westfall.
So, what do you do if you find the screen slightly off centered? David Thoresen gave clear, concise instructions on the Eos mailing list on how to fix the problem.
\"Read all the instructions first! Lay your camera on a flat table with a lot of light (Dust free area). Looking at your Eos 3 from the front without a lens or lens cap you will see a small \"latch\" in the front middle upper part of the opening, right below the red dot. If you take your fingernail or very small straight head screwdriver and pull the latch *VERY GENTLY* towards you, the gate will open easily and the focusing screen will pop down.\"
\"If it does not pop down you might be pulling at the wrong place. BE CAREFUL NOT TO TOUCH THE SCREEN! When it does pop down do not remove the focusing screen, because it\'s very difficult to clean the screen. NOTE: Sometimes just by releasing the focusing screen and pushing it back into place will center it automatically. You will see a very small 2mm piece of the focusing screen sticking out on the gate and move this part either slightly to the left or right depending on which way your rectangle problem is. This is less than a ?mm of movement.\"
\"To replace the screen, touch the metal part only and gently push the gate back into place. It should make a small \"click\" when it pops back into place. Don\'t touch the mirror when you are doing this. Look through your camera and it should all be lined up correctly. If not try again...\" -- David Thoresen, Hawaii, USA.
In case you are wondering, my Eos 3 has a perfectly centered focusing screen. The center AF point is smack in the middle of the partial metering circle. None of my other Eos 3 user friends had any problems with off-centered points either, but just in case yours does, don\'t worry, like Chuck said -- it\'s no big deal. It can be easily remedied and will not affect focusing accuracy in any way. |
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發表於 2007-7-24 20:37
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