Abstract: A method for producing polytetrafluoroethylene, which includes polymerizing tetrafluoroethylene in an aqueous medium in the presence of a nucleating agent and a hydrocarbon anionic surfactant to obtain polytetrafluoroethylene. A total amount of the nucleating agent and the hydrocarbon anionic surfactant at the initiation of polymerization is more than 50 ppm based on the aqueous medium.

Abstract: A signal processor of an electronic still camera stores image data, obtained during photographing, into a buffer memory. A gain adjusting circuit performs multiplication on the stored image data with the exposure amount changed by 0.5 EV at a time. Next, a usage-specific processor processes the image data in one of two ways to change the gradation, contour, and so on, of the image data so that the image data may be output appropriately to a CRT or a printer.

Abstract: An image-capturing EV is obtained when a shutter button is half pressed, and whether to flash an electronic flash for a subject of low luminance is determined according to the image-capturing EV. If it is determined that the electronic flash should be flashed for the subject of low luminance, a white balance is adjusted according to an electronic flash light. If it is determined that the electronic flash should not be flashed for the subject of low luminance, color information relating to a plurality of areas divided from an entire image plane is acquired, and the number of areas belonging to a shade determination frame, which indicates a color distribution range corresponding to the shade, is found according to the acquired color information. Then, whether a type of the light source is the shade or the daylight is determined according to the obtained image-capturing EV and the number of areas belonging to the shade determination frame.

Abstract: An all-white reference subject is imaged by a CCD and image data representing the reference subject is obtained. The position of any dust on the reference subject represented by the reference-subject image data is detected by a dust position detector. Address data representing the position of the dust is stored in a memory that stores dust address data. When the user images a subject, image data obtained by such imaging is input to a dust correction circuit. The dust address data is read from the memory and the image at the position represented by this dust address data is eliminated from the image of the subject by reason of the fact that the image at this position is that of dust.

Abstract: An all-white reference subject is imaged by a CCD and image data representing the reference subject is obtained. The position of any dust on the reference subject represented by the reference-subject image data is detected by a dust position detector. Address data representing the position of the dust is stored in a memory that stores dust address data. When the user images a subject, image data obtained by such imaging is input to a dust correction circuit. The dust address data is read from the memory and the image at the position represented by this dust address data is eliminated from the image of the subject by reason of the fact that the image at this position is that of dust.

Abstract: In a digital camera in which image data produced through a photographing operation is compressed to be written in a memory card, even if a shutter release button is depressed during the recording of the image data in the memory card, the photographing can be immediately achieved. While image data stored in a buffer memory is being compressed to be stored in the memory card, the depression of shutter release button is continuously monitored. If the release button is pressed, the recording operation in the memory card is interrupted to conduct the photographing. After the photographing is finished, the image data for which the recording is interrupted is compressed to be entirely written in the memory card beginning at the start point thereof.

Abstract: An object of the present invention is to bring a video signal obtained by imaging into a proper level without use of a controllable diaphragm. An imaging apparatus is provided with no controllable diaphragm. Peak detection is performed by a peak detecting circuit for each vertical scanning interval. A peak value is applied to a control device. Necessary shutter speed control in a shutter control circuit, gain control in a pre-amplifier circuit and gain control in a GCA are carried out. Consequently, the level of the video signal obtained by the imaging is adjusted to a proper level without controlling a diaphragm, to obtain an image of proper brightness.