Sensitometria 2

4 ECTS; 2º Ano, 2º Semestre, 30,0 TP + 5,0 OT

- Rui Manuel Domingos Gonçalves

Basics of mathematics.

Apprehending the concepts and techniques involved in characterizing modern photosensitive materials, so that we can improve and monitor the results in obtaining the digital photographic records.

1-Photoelectric Effect.
Experimental discovery of the photoelectric effect. Theoretical explanation of the photoelectric effect. Physical description of the dual nature of light. Quantification of radiation. Technological implementation of the photoelectric effect.
2-Digital detector.
The beginnings and the first solid state sensors. The CCD type detector. Linear sensor. Characterization and operation of the CCD physical area and the photosensitive element (pixel), storage capacity of the photosensors electrons, quantum efficiency, response spectrum and a linear response to light. Ways of pixels reading in two-dimensional sensors (matrix). The binary system and representing binary numbers. Conversion between the decimal system and the binary system. Arithmetic operations of binary numbers. Converting the analog signal to digital: the ADC converters (8, 12 and 16-bit), read noise. The electronic and thermal noise CCD chip. Bias and Dark Current (dark frame), how to obtain and use them. CCD (CMOS) chip defects: hot and cold pixels, degradation with age. Defects such as fingerprint sensor. Uniform light map (flat-field) for vignetting correction and response calibration of our optical images. Dynamics in our digital images. Reading time of the CCD sensor and size of images (files), pixels binning and formats: compressed and uncompressed images. The CMOS type detector; comparative characteristics with CCD: main advantages and disadvantages.
3-Current CCD/CMOS Color sensor.
The CCD (CMOS) color chip. Ways to obtain a color image: multi-image with multi-sensor, multi-image with multi-filter sensor, tri-filtered image sensor. Bayer filters (CFA-Color Filter Array) with the sensor; RGB or complement and its variations. Techniques and digital color calculation algorithms. The various shapes of the pixels, Mega-pixel chip sensors. Color and resolution. Noise reduction techniques. Structure of modern digital cameras.
4-Digital Performance.
Current analog-to-digital converters (ADC); 8, 10 and 12-bit. Counting pixels in the CCD; pixels used to form image - for corrections and interpolations. Factor fill and microlenses. Artifacts in digital images; blooming, chromatic aberration, jaggies, maze and moiré, blurring the edges, noise and JPEG compression. Noise reduction in digital camera for high ISO and long integration time. RAW, TIFF and JPEG image compression. Register media; current memory cards. Interpolation functions of pixels/information, its application in digital zoom. "Mistakes and Myths" common related to image/digital camera.
5-Examples of Scientific Application of Digital Image.
Images of extended sources and point sources. Image of planetary surfaces. Photometry and astrometry of stellar object.

Evaluation Methodology
A written test which evaluate the knowledge and skills acquired by the student.

- Eggleston, J. (1990). Sensitometry for Photographers. New York: Focal Press
- Eggleston, J. (1990). Sensitometry for Photographers. New York: Focal Press
- Spencer, D. (1971). Applied Photography. New York: Focal Press Limited

Method of interaction
Lectures in which they teach the concepts, principles and knowledge related to light and modes to register with modern sensors. Tests and methods of operation of modern digital systems for image registry.

Software used in class
Not applicable