Saturday, October 25, 2008

Term 4 Session 2: Megapixels & Digital Colour

(UPDATE Aug 2012 - I have removed images that won't display correctly but will leave the text here as reference)


Relative size of the various megapixel images. Note that the 5 megapixel image is about
four times the size of the 1.3Megapixel image but that the 5 megapixel image is nowhere near
twice the size of the 3.3 Megapixel image.
http://i210.photobucket.com/albums/bb41/Jim_Bell_of_Belmont/ImageSizes.jpg
If you have a 1.3 megapixel camera that take a top image size of 1280 x 960 pixels...
divide by 300;   1280 divided by 300= 4.26, and 960 divided by 300= 3.2. 
So technically, that 1.3 megapixel camera can produce a
"photo quality" photo at 300ppi of 4.26 by 3.2 inches.


A 2.1 megapixel camera will generally produce an image around 1600 x 1200 pixels in size.
(1600 divided by 300 is 5.3 and 1200
divided by 300 is 4 ....
so a 1600 x 1200 makes a 5.3" x 4" 300 dpi print)


A 3.3 megapixel camera will generally produce an image around  2048 x 1536

A 5 megapixel camera will give you an image size in the neighborhood of 2560 x 1920 pixels
(2560 divided by 300 is 8.5 and 1920 divided by 300 is 6.4 ....
so a
2560 x 1920 makes a 8.5" x 6.4"  300 dpi print)

Image:Video Standards.svg

http://upload.wikimedia.org/wikipedia/commons/c/ca/Video_Standards.svg



Image Compression ......  In order to store digital pictures economically, the image data is
compressed. However, compression often causes a reduction in picture quality.


Image Compression ...... reduction of the amount of data required to represent an image.
This is accomplished by encoding the spatial and contrast information.
Image Compression ...... minimizes the file size (in bytes) of an image.
Two of the most common compressed image formats are JPEG and GIF. ...


1bit image ie. black or white
1 bit

4 bit image 16 usable colours only
4 bits

8 bit image 256 usable colours only

8 bits

24 bit image 16,777,216 usable colours only
Truecolor (24+ bits)

RGB color model

http://en.wikipedia.org/wiki/RGB_color_model

The RGB color model is an additive color model in which red, green, and blue light are
added together in various ways to reproduce a broad array of colors.
The name of the model comes from the initials of the three additive primary colors,
red, green, and blue.

Image:RGB illumination.jpg
A representation of additive color mixing. Projection of primary color lights on a
screen shows secondary colors where two overlap; the combination of
all three of red, green, and blue in appropriate intensities makes white.
Blogged with the Flock Browser

Wednesday, October 22, 2008

Term 4 Session 1 Card Readers, Resolution

(UPDATE Aug 2012 - I have removed images that won't display correctly but will leave the text here as reference)

Sections in ITALICS are copied directly from the web site at the link above them. ie. click on
the link to read the full article and find more information.



A USB Card Reader
A USB Card Reader like this one, will typically implement the USB mass storage device class.




http://en.wikipedia.org/wiki/Photograph
"Non-digital photographs are produced with a two-step chemical process. In the two-step process the light-sensitive film captures a
negative image (colors and lights/darks are inverted). To produce a positive image, the negative is most commonly transferred ('printed') onto photographic paper. Printing the negative onto transparent film stock is used to manufacture motion picture films."

digital photography
"The advent of the microcomputer and digital photography has led to the rise of digital prints. These prints are created from stored graphic formats such as JPEG, TIFF, and RAW. The types of printers used include inkjet printers, dye-sublimation printer, laser printers, and thermal printers. Inkjet prints are sometimes given the coined name "Giclée"."

"Digital photography
is a form of photography that utilizes digital technology to make digital images of subjects. Until the advent of digital technology, photography used photographic film to create images which could be made visible by photographic processing. Digital images can be displayed, printed, stored, manipulated, transmitted, and archived using digital and computer techniques, without chemical processing.
Digital photography is one of several forms of digital imaging. Digital images are also created by non-photographic equipment such as computer tomography scanners and radio telescopes. Digital images can also be made by scanning conventional photographic images."



The main difference between the digital and analog is that digital must have a certain number of
steps or gradations but an analog representation has an infinitely fine number of steps and as such
should be able to produce a finer gradation.
As an example in a digital vs analog photo containing the sun the digital print will usually just be
smooth white but the analog may show some detail.




http://en.wikipedia.org/wiki/Pixel

"In digital imaging, a pixel (picture element[1]) is the smallest piece of information in an image.
Pixels are normally arranged in a regular 2-dimensional grid, and are often represented using
dots, squares, or rectangles. Each pixel is a
sample of an original image, where more samples
typically provide a more accurate representation of the original. The
intensity of each pixel is
variable; in color systems, each pixel has typically three or four components such as

red, green, and blue, or cyan, magenta, yellow, and black."

This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen.
"This example shows an image with a portion greatly enlarged, in which the individual
pixels are rendered as little squares and can easily be seen."

A photograph of sub-pixel display elements on a laptop's LCD screen
"A photograph of sub-pixel display elements on a laptop's LCD screen"
That is to say the red, green and blue bar work together to make one pixel

A pixel does not need to be rendered as a small square.  This image shows alternative ways of reconstructing an image from a set of pixel values, using dots, lines, or smooth filtering.
"A pixel does not need to be rendered as a small square. This image shows alternative
ways of reconstructing an image from a set of pixel values, using dots, lines, or smooth filtering."








Blogged with the Flock Browser