Digital Image-M.V.Ramachandranwww.youtube.com/postmanchandru

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Digital Camera

• Digital Cameras convert analog into digital information

• Represented by ones and zeros, or bits

What’s the difference between a digital camera and a regular film camera?

What’s the difference between a digital camera and a regular film camera?

• Film cameras depend on chemical and mechanical processes

• Film cameras do not even need electricity• Digital Cameras have a built in computer

which record images electronically

Digital camera and a Regular film camera

• A Digital Cameras has different lenses that help focus the light to create the images

• A 35 mm camera would focus the light onto a piece of film….

• a Digital Cameras focus the light onto a semi-conductor device that records the light electronically– A computer breaks this info down

into digital data

What breaks down the info into digital data?

• A sensor converts the light into electrical charges

• Digital Cameras use CCDs (Charged Couple Devices) or CMOS (Complementary Metal Oxide Semiconductor)– Both convert light into electrons– Value is read of each cell in the image– Both operate similarly converting the light

into readable form

CCD CMOS

• Although numerous differences exist between the two sensors,

• They both play the same role in the camera -- they turn light into electricity.

• To understand how a digital camera works, you can think of them as nearly identical devices.

What’s the real difference• Because each pixel on a CMOS

sensor has several transistors located next to it, the light sensitivity of a CMOS chip is lower.

• CMOS sensors traditionally consume little power.

• CCDs, on the other hand, use a process that consumes lots of power.

• CCDs consume as much as 100 times more power than an equivalent CMOS sensor.

• CCD sensors create high-quality, low-noise images.

• CMOS sensors are generally more susceptible to noise.

• CCD sensors have been mass produced for a longer period of time, so they are more mature.

• They tend to have higher quality pixels, and more of them.

What else is important in a Digital Cameras?

• Resolution– The amount of detail that the camera can

capture and it is measured in pixels. – The more pixels a camera has, the more

detail – it can capture and the larger pictures can

be without becoming blurry or "grainy."

Common Resolutions• 256x256 - Found on very cheap cameras, this resolution is so low that the picture

quality is almost always unacceptable. This is 65,000 total pixels.

• 640x480 - This is the low end on most "real" cameras. This resolution is ideal for e-mailing pictures or posting pictures on a Web site.

• 1216x912 - This is a "megapixel" image size -- 1,109,000 total pixels -- good for printing pictures.

• 1600x1200 - With almost 2 million total pixels, this is "high resolution." You can print a 4x5 inch print taken at this resolution with the same quality that you would get from a photo lab.

• 2240x1680 - Found on 4 megapixel cameras -- the current standard -- this allows even larger printed photos, with good quality for prints up to 16x20 inches.

• 4064x2704 - A top-of-the-line digital camera with 11.1 megapixels takes pictures at this resolution. At this setting, you can create 13.5x9 inch prints with no loss of picture quality.

Types of Digital Camera

Digital Image Recording

How do Digital Camerascapture color?

• Photosets are blind• Photosites only keep track of the total

intensity of light that strikes the surface• To get full color of an image, most sensors

use filtering to look at the light in its three primary colors

• All three colors get recorded and combined to create the full spectrum

Exposure & Focus

• Digital camera has to control the amount of light that reaches the sensor.

• The two components it uses to do this, the aperture and shutter speed, and are also present on conventional cameras.

Exposure & Focus

• Aperture: The size of the opening in the camera. – The aperture is automatic in most digital cameras, but

some allow manual adjustment to give professionals and hobbyists more control over the final image.

• Shutter speed: The amount of time that light can pass through the aperture. – Unlike film, the light sensor in a digital camera can be

reset electronically, so digital cameras have a digital shutter.

Exposure & Focus

• Aperture and shutter speed work together to capture the right amount of light needed to make a good image

• The camera also adjusts the lenses to control how the light is focused on the sensor.

• Most Digital Cameras use auto focus lenses

Focal Length

• This is the biggest difference between a digital camera and a regular conventional camera

• So what is focal length…– The distance between the lens and

the surface of the sensor– This determines the magnification

(zoom)– Increasing the focal length increases

the zoom / magnification and vice versa

Digital Camera Lenses

• Fixed-focus, fixed-zoom lenses - These are the kinds of lenses on disposable and inexpensive film cameras -- inexpensive and great for snapshots, but fairly limited.

Digital Camera Lenses

• Optical-zoom lenses with automatic focus - Similar to the lens on a video camcorder, these have "wide" and "telephoto" options and automatic focus.

• The camera may or may not support manual focus. These actually change the focal length of the lens rather than just magnifying the information that hits the sensor.

Digital Camera Lenses

• Replaceable lens systems - These are similar to the replaceable lenses on a 35mm camera. Some digital cameras can use 35mm camera lenses.

Storage

• Early generations of digital cameras had fixed storage inside the camera.

• You needed to connect the camera directly

to a computer with cables to transfer the images.

Storage

• Today's cameras are capable of connecting through serial, parallel, SCSI, USB or FireWire connections

• They usually also use some sort of removable storage device.

Storage

• Removable storage devices include: – Floppy disks – Hard disks, or microdrives – Writeable CDs and DVDs

File Format

• Jpeg• TIFF• RAW

JPEG

JPEG

RAW

TIFF

Resolution

• Quality of the pictures on a screen, print, or file– DPI = dots per inch (printer)– PPI = pixels per inch (screen)

• More resolution means higher file size• Different file types contain more or less

information (resolution)

Understanding pixels

• Picture elements (dots) per inch• Standard monitor displays 640 by 480 pixels

– 640 by 480– 1024 by 768

• More pixels requires more RAM, which may mean lower bit depth

Enlarging with pixels

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