Digital camera and exposure condition determining method
To provide a digital camera capable of causing a focus sensor to detect a focus while outputting to an image sensor image data for providing appropriate exposure after having adjusted an aperture ratio of an aperture in an image capture optical system such that appropriate exposure is achieved. A digital camera divides light from a subject having passed through an aperture into two beams of light; causes one of the beams to enter the image sensor to thus cause the image sensor to capture a subject image; and causes the other beam to enter the focus sensor to thus cause the focus sensor to detect a focus from the other beam of light. The digital camera adjusts an aperture ratio of the aperture such that the quantity of the other beam reaches the minimum quantity of light at or above which the focus sensor can detect a focus.
1. A digital camera which divides light having come from a subject and passed through an aperture into two beams of light; which causes one of the divided beams of light to enter an image sensor to thereby cause the image sensor to capture an image of a subject; and which causes the other one of the beams of light to enter a focus sensor to thereby cause the focus sensor to detect a focus on the basis of the other beam of light, the camera comprising:
an exposure condition determining section for determining exposure conditions, including an aperture ratio of the aperture, under which the image sensor can capture an image at appropriate exposure, in accordance with the quantity of light from the subject, wherein,
when the focus sensor cannot detect a focus on the basis of the other one of the beams of light divided after having passed through the aperture, at the aperture ratio determined by the exposure condition determining section, the exposure condition determining section fixes the aperture ratio of the aperture at a minimum aperture ratio at or above which the focus sensor can detect a focus, to thus determine the exposure conditions.
2. The digital camera according to claim 1 , further comprising:
a focus control section for causing the focus sensor to detect a focus while maintaining the aperture at the minimum aperture ratio during the course of the image sensor consecutively outputting image data on the basis of the light from the subject.
3. The digital camera according to claim 2 , further comprising:
an image record control section for recording, among a plurality of frames of image data consecutively output by the image sensor until receipt of an image capture instruction, a frame of image data preceding, by a predetermined time lag period, a frame of image data captured at the time of receipt of the image capture instruction, as an image data for storage purpose in storage memory.
4. The digital camera according to claim 2 , wherein the focus control section causes the focus sensor to detect a focus every time the image sensor outputs a predetermined number of frames of image data.
5. The digital camera according to claim 2 , wherein the focus control section causes the focus sensor to detect a focus every time the image sensor outputs one frame of image data.
6. The digital camera according to claim 5 , further comprising:
a focus processing section for performing focus processing in response to a result of focus detection effected by the focus sensor from when the image sensor has completed exposure processing for one frame until the image sensor starts exposure processing for a subsequent one frame.
7. The digital camera according to claim 1 , further comprising:
a control section for, upon receipt of an image capture stop instruction, maintaining the aperture at the minimum aperture ratio for a predetermined standby period from receipt of the image capture stop instruction.
8. The digital camera according to claim 7 , wherein the control section maintains the aperture at the minimum aperture ratio for the standby period, and maintains current positions of a group of image capture lenses provided in the digital camera.
9. A digital camera which divides light having come from a subject and passed through an aperture into two beams of light; which causes one of the divided beams of light to enter an image sensor to thereby cause the image sensor to capture an image of a subject; and which causes the other one of the beams of light to enter a focus sensor to thereby cause the focus sensor to detect a focus on the basis of the other beam of light, the camera comprising:
an exposure condition determining section for determining exposure conditions, including an aperture ratio of the aperture, under which the image sensor can capture an image at appropriate exposure, in accordance with the quantity of light from the subject, wherein,
the digital camera can operate in at least a normal image capture mode where the image sensor outputs one frame of image data upon receipt of the image capture instruction and a consecutive image capture mode where the image sensor consecutively outputs image data until receipt of the image capture instruction; and wherein,
when the digital camera operates in the consecutive image capture mode and the focus sensor cannot detect a focus at the aperture ratio determined by the exposure condition determining section, on the basis of the other beam of light divided after having passed through the aperture, the exposure condition determining section fixes the aperture ratio of the aperture at a minimum aperture ratio at or above which the focus sensor can detect a focus, to thus determine the exposure conditions.
10. An exposure condition determining method for determining exposure conditions, including an aperture ratio of the aperture, under which an image sensor can capture an image at appropriate exposure, in accordance with the quantity of light from a subject, in relation to a digital camera which divides light having come from a subject and passed through an aperture, into two beams of light; which causes one of the divided beams of light to enter an image sensor to thereby cause the image sensor to capture an image of a subject; and which causes the other one of the beams of light to enter a focus sensor to thereby cause the focus sensor to detect a focus on the basis of the other beam of light, wherein,
when the focus sensor cannot detect a focus on the basis of the other one of the beams of light divided after having passed through the aperture, at the determined aperture ratio, the aperture ratio of the aperture is fixed at a minimum aperture ratio at or above which the focus sensor can detect a focus, to thus determine the exposure conditions.
11. An exposure condition determining method for determining exposure conditions, including an aperture ratio of the aperture, under which an image sensor can capture an image at appropriate exposure, in accordance with the quantity of light from a subject, in relation to a digital camera which divides light having come from a subject and passed through an aperture, into two beams of light; which causes one of the divided beams of light to enter an image sensor to thereby cause the image sensor to capture an image of a subject; and which causes the other one of the beams of light to enter a focus sensor to thereby cause the focus sensor to detect a focus on the basis of the other beam of light, wherein,
the digital camera can operate in at least a normal image capture mode where the image sensor outputs one frame of image data upon receipt of the image capture instruction and a consecutive image capture mode where the image sensor consecutively outputs image data until receipt of the image capture instruction; and wherein,
when the digital camera operates in the consecutive image capture mode and the focus sensor cannot detect a focus at the aperture ratio determined by the exposure condition determining section, on the basis of the other beam of light divided after having passed through the aperture, the exposure condition determining section fixes the aperture ratio of the aperture at a minimum aperture ratio at or above which the focus sensor can detect a focus, to thus determine the exposure conditions.