Fundamentals of Photoshop

Digital Imaging

Pixel

• A small square of light. The smallest portion of an image a computer is able to display or print

• Picture + Element = Pixel

• Term was created in 1965 by NASA

Pixel

• A pixel is a portmanteau

• Portmanteau: a combination of two words.

• Examples: smog, brunch, cellphone, email

Megapixel

• A simple unit of storage equalling 1 million pixels.

• A term commonly used to describe how much data a camera can capture.

• Example: If your camera can capture 2048x1536 pixels, it is referred to as having 3.1 megapixels (2048x1536 = 3,145,728)

Megapixel

• How many megapixels are right for me?

• More does not mean better

• Just because a car holds more fuel doesn’t mean it is faster, more efficient, as reliable

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Megapixel

• If a 3.1 megapixel image were printed at 300 ppi (pixels per inch) it would be roughly 5”x7” print.

• That isn’t enough for a professional photographer but might be plenty for a consumer.

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Megapixel

• The more pixels you capture the larger the image is, both in disk space and print size).

• An inkjet printer and emailing demands less pixels than do professional printing machines.

Cool Facts

• With a 3 megapixel camera you can take higher resolution images than most computer monitors can display

• The first consumer-oriented digital cameras were made by Kodak and Apple in 1994.

• In 1998, Sony inadvertently sold more than 700,000 digital camcorders with a limited ability to see through clothes.

Megapixel Myth

• More megapixels does not mean a better picture.

• Rather than buying more pixels look at the quality of the lense or options that are more important to you (auto/manual functions, low light capabilities, battery life)

Resolution

• DPI: Dots Per Inch. Refers to number of dots per inch a printer can produce. Not appropriate term for cameras or scanners.

• PPI: Pixels Per Inch. Refers to number of pixels per inch a digital image contains. Most monitors display 72 ppi (though many now are adjustable).

Resolution

• SPI: Samples Per Inch. This is a more specific term used for scanners. A sample is a scanned part of an image.

• Scanner Advice: Always choose a scanner with high optical resolution rather than digital resolution.

Resolution

• LPI: Lines Per Inch. Traditional process of converting a photograph into a series dots called a halftone. The higher the lpi the smoother the image (most newspapers and magazines use this process).

Image Mode

• There are 8 image mode settings in Photoshop.

• The 3 most common are RGB, CMYK, and Grayscale.

RGB

• Most common mode for graphics.

• RGB uses additive color theory to represent color

• 100% value of red, green, and blue equals white

• By varying amounts of each color almost every color intensity can be created.

CMYK• Professional printers use a four-color process to simulate color.

• Cyan, Magenta, Yellow, Black (K stands for Key)

• CMYK uses reductive color theory. It deals with what part of color wavelengths are not reflected to create light.

• Cyan + Magenta + Yellow = Black• Cyan + Magenta = Blue• Magenta + Yellow = Red• Cyan + Yellow = Green• Black is the Key Color. In other words, it is used in fine detail areas

and text to create depth in color and crisp detail. The “key” ties everything together.

Example of CMYK Colors

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CMY Image Breakdown

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Grayscale

• Uses different shades of Gray to represent image details.

• An 8-bit image has 256 levels of gray. A 16-bit image has 65,536 levels of gray.

Bitdepth

• Measures how much color is available for display or printing of each pixel.

• A greater bit depth means each pixel contains more information for describing color.

• A pixel with a bit depth of 1 can only describe black or white.

• Most common bit depth is 8, which can display 256 intensity levels of color.

Duotone

• Can be a monotone, a duotone, tritone, or quadtone.

• It is a grayscale image that uses other colors.

• Example: Sepiatone

Bitmap

• Uses only one of two color values, black or white, to represent the pixel data.

• Creates a very small file size.

Indexed Color

• Limits the amount of colors available to 256.

• Used often for web images to reduce file size and speed up screen load times and download times.

L.a.b.

• L.a.b. color is the most complete color mode used to describe colors to the human eye.

• The three parameters are L for luminance, “a” for the color’s position between red and green, and “b” for its position between yellow and blue.

Multichannel

• A highly specialized mode used for complex color separations for professional printing.

• Rarely used by photographers and consumer-based users.