Seeing the Flicker Flicker and Apparent Motion are different phenomena! Flicker and Apparent Motion are different phenomena! Flicker and Apparent Motion are different phenomena!
Graphics vs. Images Some definitions: mine for clarity here: Graphics Def: computer generated or drawn by you. Image: scanned, captured, take photograph or an graphic file not generated by you. Difference: In a graphic, you can directly manipulate the elements because you drew them – Sprites In an image, you can manipulate pixels but not directly the elements. This has a great impact.
Images or Graphics on the Screen Pixels: smallest picture element Pixels are not screen dots!!! Several dots (at least three, one of each color) make up each pixel) Bitmat: An array of information that contains the information for the image. It is a 3 dimensional array Width x Height x 24 (8 for each color) So can be huge (.bmp and.tif or.tiff are most common bitmaps)
Graphic and Image Formats Bitmap (bmp, PCT, Tiff) – big, not good for web Graphic Interchange Format (Gif) can animate 8 bits of color – palette or lookup table or LUT – no loss of spatial information Can be some legal issues – make sure the generator legally can generate GIF’s Generally best compression for simple graphics – bad for photos Can generate transparent regions Can Animate
Graphics and Image Formats JPG Generally better for images and photos Spatial not color compression, can distort image spatially and more loss with each save Now can animate as well.
BMP vs JPEG File Sizes Both images are the same relative size..BMP 900kb.JPEG High Quality ~700kb
ImageJ Free at: http://rsb.info.nih.gov/ij/index.html http://rsb.info.nih.gov/ij/index.html Overview Java program Interface a bit awkward because it is free Expandable via plug-ins Covers all basic editing and many advanced - very advanced Scientific quality image editor Used in many technical applications
Chromatic Issues Chromatic Issues The Trichromatic Theory The Trichromatic Theory Color Opponent Theory Color Opponent Theory Color Picker Color Picker The Color Gamut Glare Color Blindness
The CIE Color System The CIE Color System A set of Equations that allow predictions of matching. Used in photo printing, TV and film. Wyszecki & Stiles (1967) The Color Gamut The range of colors reproducible by any system
The Color Gamut The Color Gamut The range of colors reproducible by any system
The Effect of Illuminance on Gamut In Dark With Lights on and 30% Luminance Level
Illuminance Agostini & Bruno (1996) Accuracy of the perceived stimulus is affected by the amount of illuminance. D. F. Neri (1990) Combination of light and gamut changed chromaticity Request close windows and turn off unnecessary light Do not use subtle color differences
Effects of Edges Craik-Cornsweet and Minimal Contours Craik-Cornsweet and Minimal Contours Craik-Cornsweet and Minimal Contours Why these effects? Why these effects? Why these effects?
Anti-aliasing Solution to aliasing Bandlimiting or anti-aliasing Essentially blur the edges or image so fine detail is lost In a lot of Software Ideally use a gaussian filter This is the shape of CRT electron beam which is why dots on screen never show up Infante (1985); Silverstein et al. (1990) Many graphics software and even some languages anti-alias (Java2D) but it is not calibrated but good enough with sufficient resolution
Digital Cameras No loss in Scanning CCD 3.1 Megapixel at least if need photo quality and larger They can get huge these days Can use lower image if only need web But do not sacrifice image quality Easy to download Can be good in low light
Taking Photos Digitally Focusing: Automatic and Manual Regular focus Macro – allows focusing up close Spot Focus: focus is determined by point Shutter Speed Zoom: Do not use digital zoom – if need more zoom, do it on computer later On my camera: default is digital zoom off except for movies
Taking Pictures (cont.) White Balance, controls for our color constancy White Balance, controls for our color constancy White Balance, controls for our color constancy Effect of the Illuminant Effect of the Illuminant Effect of the Illuminant Flash: often I keep it off. Image Size: I keep at standard (full pixel density, some JPG compression). Balance between image quality and ability to store on disk ~ 1 Meg/picture
Use of Flash FlashNo Flash Watch for reflections. Can get inexpensive table camera tripods.
Brightness and Contrast Visual Measures Visual Measures Visual Measures Visually separate but tied together on computer
Assignment Take series of images that you might want shown in sequences as part of a study