Mike Brown |
December 14th, 2006 06:08 AM |
Quote:
Originally Posted by Jim Harmon
I took my HV10 out for the first time today; it was a bright, sunny afternoon, about 2:00 pm. I took some photos in Card mode and some of the same scene by snapping a photo during taping in Camera mode. I just compared EXIF info of the various shots; it seemed to keep the same f number, but vary the shutter.
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The patent text describes a different control scheme for still shots than for video. One reason mentioned is that shutter speed can go much slower (below 1/30th second) in still mode, as compared to video. Also, it says that image smear can be prevented by using a mechanical shutter in still mode. A more complicated control scheme for still shots using the internal ND filter is described as follows:
Quote:
Combinations of the densities of the ND filter and the F-numbers of aperture control at individual EVs will be explained below with reference to FIG. 11B. In the region where the EV is 2 (inclusive) to 8 (exclusive), the shutter speed lowers in accordance with each EV, but the F-number of aperture control is fixed to F2 as an open-aperture F-number, and the number of ND steps of the ND filter is also fixed to 0. That is, the transparent portion 151a shown in FIG. 2 of the ND filter 151 is used in this region.
In the region where the EV is 8 (inclusive) to 11 (exclusive), the shutter speed is continuously variable from 1/60 to 1/125 sec, the F-number of aperture control is continuously variable from F2 to F4, and the number of ND steps of the ND filter is fixed to 0.
When the EV is 11 or more, the F-number of aperture control is returned from F4 to F2, and the number of ND steps of the ND filter is switched from 0 to 2. (Referring to FIG. 11B, the switching points of the F-number and the number of ND steps are different. In practice, however, the F-number and the number of ND steps are simultaneously changed.) That is, in this stage, the uniform-density portion 151b having an optical density of 0.6 shown in FIG. 2 of the ND filter 151 is used.
In the region where the EV is 11 (inclusive) to 14 (exclusive), the shutter speed is continuously variable from 1/125 to 1/250 sec, the F-number of aperture control is continuously variable from F2 to F4, and the number of ND steps of the ND filter is fixed to 2.
When the EV is 14 or more, the F-number of aperture control is returned from F4 to F2, and the number of ND steps of the ND filter is switched from 2 to 4. That is, in this stage, the uniform-density portion 151c having an optical density of 1.2 shown in FIG. 2 of the ND filter 151 is used.
In a region where the EV is 14 (inclusive) to 17 (exclusive), the shutter speed is continuously variable from 1/250 to 1/500 sec, the F-number of aperture control is continuously variable from F2 to F4, and the number of ND steps of the ND filter is fixed to 4.
In a region where the EV is 17 (inclusive) to 19 (exclusive), the shutter speed is continuously variable from 1/500 to 1/2000 sec, the F-number of aperture control is fixed to F4, and the number of ND steps of the ND filter is kept fixed to 4. The exposure control diagram described above is applied to single-shot photographing or photographing of the first frame in continuous photographing.
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The main difference between this still shot control scheme and the one for video is that the iris is held between f2 and f4, whereas for video it stops down to f8 (said to be the limit owing to small-aperture diffraction problems that develop with tight pixel pitch at higher f-stops).
Another still shot control scheme without ND filters is also described, so it is not 100% clear that the one quoted above is being used. Also, nothing in the patent specifically references the HV10 camcorder. However, Canon's HV10 publicity referring to the "patented Gradation ND" system strongly suggests that one of the schemes mentioned in the patent is being used.
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