iam11_lecture04

Aperture measured by the quotient f d focal

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: de-angle lens, longer focal length: tele lens. 9 10 • Exposure time. Standard scale: 1 1 1 1 1 1 1111 1000 , 500 , 250 , 125 , 60 , 30 , 15 , 8 , 4 , 2 , 1 s. • Aperture. Measured by the quotient f /d =focal length/aperture diameter. Standard scale: 1 (large), 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45 (small). • Sensitivity. Given in ISO scale. Typical general-purpose films range around ISO 100, moderate high-speed films ISO 400, extreme high-speed ISO 3200. - ISO 400 or higher typically leads to noticeably increased noise. - CCD cameras also allow setting ISO-equivalent sensitivity. 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Sources of Image Degradation in Visible Light Photography Sources of Image Degradation in Visible Light Photography 12 34 Important Degradations 56 • Motion blurs: Caused by movement of objects or camera during exposure. 78 • Aberrations: Imperfection of camera optics (spherical/chromatic). 9 10 • Diaphragm diffraction: Imperfection of camera optics. Diffraction occurs at the edges of the diaphragm used to adjust aperture. As a result, points are blurred depending on the shape of the diaphragm. 11 12 • Defocussing: Misadjustment of camera optics. Results in disk-shaped blur. 15 16 • Grain: Physical limitation of photographic film. 17 18 • Mosaic: A problem specific to digital colour photography. See next lecture. 19 20 • Quantum noise: Physical perturbation in CCD sensors. 21 22 13 14 23 24 25 26 27 28 Summary 12 Summary 34 Lenses bend light beams by refraction. 56 An ideal convex lens can be used to create an upside-down real image. 78 Real lenses suffer from aberrations such as spherical and chromatic aberrations. Some aberrations can be reduced by lens systems. 9 10 The pinhole camera is the simplest camera model (no lenses). A camera with lens(es) requires focussing. 11 12 13 14 Fechner’s law states a logarithmic brightness impression. 15 16 Photochemical films and electrophotography create analog images. 17 18 Semiconductor photosensors create a photocurrent that can be separated and collected in CCD sensors. They give digital images. 19 20 Active pixel sensors such as the CMOS sensors allow a nonlinear amplification. With a logarithmic response one obtains high dynamic range sensors. 21 22 23 24 25 26 27 28 Literature Literature 12 34 B. J¨hne, H. Haußecker, P. Geißler (Eds.) Handbook of Computer Vision and Its Applications. a Volume 1: Sensors and Imaging. Academic Press, San Diego 1999. (Chapter 4 of Geißler deals with imaging optics, Chapter 7 by Seitz describes sensors) W. Greulich (Ed.) Lexikon der Physik in sechs B¨nden (in German). Spektrum, Heidelberg 1998. a (additional information on physics) 56 78 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28...
View Full Document

Ask a homework question - tutors are online