Digital Cameras

Basic Info on Operations Class Web Quest

How do digital cameras work?

Digital Cameras convert analog information (represented by a fluctuating wave) into digital information (represented by ones and zeros, or bits). CDs, DVDs, HDTV, MP3s and DVRs are all built around the same basic process

What’s the difference b/w 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

What happens when a Digital Cameras takes a picture?

Once a pic is taken the image /pic must be converted into a form the computer recognizes…bits and bytes A digital pic is just a long string of pixels …1s and 0s – All of these pixels make up the image

To help the process along…

A Digital Cameras has different lenses that help focus the light to create the image of a scene 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

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. Many of the photons hit the transistors instead of the photodiode. 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.

Confused?

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 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

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

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.

How do Digital Cameras capture color?

Photosets are blind Photosets 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

Capturing Color

Beam splitter – directs light to different sensors and each sensor only responds to one of the primary colors Rotate – all three colors (red, green , blue) get rotated in front of a single sensor; 3 separate images get recorded Color filter array – most economical and practical method used to permanently place a filter over each photosite.

– Sensor gets broken up into r,g, b pixels

Bayer filter pattern

– Most common and alternates a row of red and green filters with a row of blue and green filters.

– [pixels are not evenly divided (as many green as there are blue and red combined) • Why?

• Human eye is not a sensitive to all three colors • Necessary to include all of green so as to create an image that they eye will perceive a true color

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

shutter rather than a mechanical

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

Digital-zoom lenses

With digital zoom, the camera takes pixels from the center of the image sensor and

interpolates

them to make a full-sized image. Depending on the resolution of the image and the sensor, this approach may create a grainy or fuzzy image. You can manually do the same thing with image processing software - simply snap a picture, cut out the center and magnify it.

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

Digital cameras use various storage systems.

These are like reusable, digital film, and they use a caddy or card reader to transfer the data to a computer. Many involve fixed or removable flash memory. Digital camera manufacturers often develop their own proprietary flash memory devices, including SmartMedia cards, CompactFlash cards and Memory Sticks.

Storage

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