The image size of the Sun when photographed depends on the focal length of your camera (or telescope) focal length. Longer focal lengths produce larger images. See Relative Image Size.

However, if your camera/telescope does not have a clock motor drive to follow the Sun across the sky (an effect of Earth's rotation), images may blur if exposures times are too long. Since long focal lengths produce larger images, exposure times must be shorter to avoid image blurring. (Also see Exposure Times).

The following table gives examples of approximate longest exposure times for both critical work and for images where some blurring is not objectionable for photography without a clock drive. The last column also give the approximate diameter of the solar disk (in mm) without its corona for the focal lengths listed. (See box below table for formula.)