Book Topics and Notes:

Chapter 3: How Digital Cameras Work

2nd Edition:

The Lens

Focal Length

From a practical point of view, focal length can be thought of as the amount of a lens's magnification.

Also effects compression of the scene, perspective and Depth of Field

Fixed lenses

Zoom

Optical Zoom

Digital Zoom

Interchangeable Lenses

Lens Speed

Measures the amount of light the lens ttransmits at maximum aperture

A fast lens is more desirable and is usually more expensive

can also help the lens focus

Lens Quality

Effects image quality

Recognizing Lens Problems

Sharpness

Distortion

Pincushion Distortion

Straight lines near the edges of an image bend inward

Barrel Distortion

Bulging of the scene, straight lines near the edge of the image bend outward

Chromatic Aberation

May create colored halos at bright edges of an image

The Viewfinder and LCD

Advantages and Disadvantages

Can check lighting, composition, holding away from the eye

Uses a lot of power, hard to see on a bright day

LCD vs Viewfinder

Parralax error

The Shutter

Many digital cameras don't use a mechanical shutter

Pushing the button

A more inexpensive camera will be slower to respond

Shutter lag time

You might be able to depress the shutter halfway to decrease it

More expensive cameras often have less

The Imaging Sensor

Types of Sensors

CCD

CMOS

CCD vs CMOS

CCD still more common, but CMOS getting better

CCD uses more power and costs more to produce

Other sensors

Fuji Super CCD Sensor

Octagonal pixel shape

Foveon X3 Sensor

Sees all colors

Scanning backs

often scan 3 times, 1 for each color

only good for still objects

How Sensors Work

Blooming

When too many photons hit a particular pixel and the electrical charge becomes more than it can handle, the charge starts to overflow into surronding pixels.

Analogue to digital conversion

The process by which analogue signals are converted into discrete digital values.

Conversion quality

Noise

Amplification of the signal, such as shooting at a high ISO rating, or heat can increase noise.

ISO

When to change ISO

Only if you have to

Physical size of the sensor

Impact on Focal length

When an imaging sensor is smaller than the film it replaces, it's cropping the image circle projected by the lens.

Wide angle lenses aren't so wide angle.

Impact on Image quality

Lenses tend to be sharpest at the center, so the cropping of the image by the image sensor may produce a sharper image.

Physical size of the pixels

Impact on ISO

Larger pixels have more surface area to absorb light, giving them a higher sensitivity, or higher effective ISO.

Impact on Image Quality

Larger pixels produce an image that is coarser because they are not able to capture as much dertail; smaller pixels resolve finer detail.

Because smaller pixels are less sensitive, the signal they produce will generally need to be amplified, resulting in more noise.

Bit Depth

Higher bit depths are better for providing extra info if needed for substantial tonal and color image editing.

Usually only available with RAW Capture mode.

Capturing Color

Filter patterns

Moire patterns

Imaging sensors are color blind; they only measure brightness.

Dynamic Range

Is the ability to capture an image with full tonal detail from bright highlights to dark shadows.

If your camera doesn’t provide an adequate dynamic range to hold detail in all tonal values in your image, it’s best to underexpose the scene by 1/2 to 1 stop. Areas that are too bright and contain no information can’t be fixed. It’s better to lighten a dark image than darken a light one.

Also recommended to not use in camera options to increase image contrast or saturation.

Storing the image

compact flash, microdrive, smartmedia, memry stick, xD-Picture Card

Flash

On-Camera

Lack of control and red eye can be problems

Off-camera

Better control of exposure and effect of the lighting

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


1st edition

Many cameras use the diaphragm to shield the image sensor, and have no shutter.

No shutter means no shutter noise.

The lens element refracts light from the real world onto the image sensor.

The number of pixels captured by the image sensor is commonly known as the resolution.

Megapixel=Millions of pixels in an image.

Higher resolution images have more detail.

More compression effects image quality.

CCD vs CMOS

Digital camera file formats

JPEG: Joint photographic experts group.

JPEG's use compression and are lossy(doesn't change pixels).

TIFF: Tagged Image File Format. Has little compression and is lossless. Can be used for printing.

TIFF's

Storage media:

 

Chapter 4: The Mechanics of Digital Imagery

A word processor uses 8 bits to express a character for type. A grayscale image uses this much memory to store the data for 1 pixel.

A black and white image contains 1 bit per pixel(each pixel is black or white), a grayscale image contains 8 bits per pixel for 256 shades of gray, and a full color image contains 24 bits per pixel, showing 16.8 million colors.

Downsampling means to reduce the number of pixels by interpolating the colors of the existing pixels.

Images for the web are usually saved at 72 dpi, but browers will probably ignore the actual resolution and show the image at a 1 to 1 zoom ratio. You see 1 image pixel for every screen pixel.

For print, the resolution of the image should be about 2 times the screen frequency.
Printer Ideal Resolution(2 x screen frequency) Good Enough(1.5 x screen frequency) Absolute Maximum(2.5 x screen frequency)
300-ppi Laser printer 120 ppi 90 ppi 150 ppi
600-ppi Laser printer 180 135 225
Newsprint 180 135 225
Coated Magazine Stock 267 200 330
Super-fine Magazine Stock 350 260 440

GIF (graphic Interchange Format)

Other file formats

EPS(encapsulated postscript) used for printing.

PDF(portable document format) good for exchanging documents on disk or over the web. Requires viewer to see.

PNG(Portable Network Graphic) Web file format which hasn't caught on.

Chapter 5: Bells and Whistles: The Digital Camera Interface

Rangefinder verses SLR(Single-Lens-Reflex). Parallax error with rangefinders.

Connections:

Serial: 150 to 230 kilobits per second

USB(Universal Serial Bus): 12 megabits(1.1 Megabytes) per second. Hot swappable.

USB 2:480 megabits per second? Not widely supported yet.

Firewire(IEEE1394) 400 megabits per second.

Cardreaders and adapters.

Flashpath adapter.

PCMCIA Cards.

Camera Features

Fixed focus

Autofocus

Manual Focus

Macro Function

Automatic flash

Red-eye reduction

Fill flash

Optical zoom

Chapter 9: Essentials of Photography

Seeing the Light

  1. Brightness
  2. Size
  3. Color
  4. Number of light sources
  5. Distance
  6. Direction

Metering Patterns

  1. Center weighted
  2. Spot
  3. Multi-segment

Working with the light meter

Use a gray card or object

Push shutter button halfway and reframe.

Exposure compensation overages the light meter.

for example, Sunny or snowy beach calls for +.5 or +1 compensation.

Beating backlight(3 possible methods)

  1. Expose for subject only
  2. Add light(fill flash)
  3. Combine 2 exposures

The Digital Zone system

Exposure partners-ISO, Aperture and Shutter Speed

Relative to the human eye, the dynamic range of a CCD is very limited.

Three factors define the correct exposure: the sensitivity of the CCD, the strength of the light striking the CCD, and the length of time the CCD is exposed. The shorter the range of tones you have to work with, the more important it is to get the exposure right-to not overexpose the highlights or let the shadows block up.

Aperture and Shutter Speed

Aperture and shutter speed work together to control the exposure by determining how much light falls onto the CCD to make the picture. Think of the lens/aperture combination as a funnel, in which the big end is the lens(it gathers the light)and the small end is the aperture that controls how much light gets to the CCD in given period of time. In this analogy, the shutter is the valve that controls how long the light flows onto the CCD.

Aperture is measured in f-stops(the ratio between the focal length of the lens and the diameter of the opening in the diaphragm) and each stop in the standard series of stops represents a factor of two in the amount of light admitted.

Slow shutter speed effects

Aperture and Depth of Field

Aperture effects depth of field. The lens focuses only light from a certain distance onto the sensor, and depth of field is the measure of how much nearer or farther than that distance an object can be and still be acceptably sharp. The smaller the aperture, the greater the depth of field and the more of the photograph is in focus.The distance from the camera to the subject also plays an important role; close-ups have much more limited depth of field than landscapes do.

Depth of field is a function not only of aperture and distance from camera to subject, but of the focal length of the lens and the CCD size as well. The wider the lens, and the smaller the CCD, the greater the inherent depth of field the camera will produce.

Lenses

A normal lens has an angle of view more or less like what you see with your eyes.

A wide angle lens has the effect of extending the field of visioninto the periphery and exaggerating the dens of depth. Telephoto lenses have a narrow field and give the impression of compressing distance.

Many camera have zoom lenses that allow a choice of working focal length. Because CCD's come in a variety of sizes, manufacturers usually translate their focal length into 35mm equivalents, with 50mm being normal, above 50 being telephoto, and below 50 being wide-angle.

Don't use a wide angle for portraits.

If you're doing macro work(extreme close-up), turn off the flash and use a tripod.

Modifying the light

Softer light has lower contrast, and shadows aren't so harsh, and portraits in these conditions are much more flattering.

You can soften the light by bouncing light into the shadows with a white board(foamcore) or a collapsible reflector. Or, you can look for a wall that is reflecting light. You could also diffuse the light by having the person sit under a large white piece of material or a tree to soften the light.

Flash settings

  1. Off
  2. On
  3. Fill
  4. Auto
  5. Red-eye reduction

Flash is useful on sunny days to reduce contrast and fill shadows(fill flash). Also adds tiny 'catchlights' or specular highlights to a persons eyes(good).

Softening the flash with a third-party softbox or bounce system helps avoid blowing out the light areas of the image. Or, rubber band a white piece of paper to your flash and point the flash up.

Ways to reduce red eye

  1. Turn up the lights
  2. Use red-eye reduction flash
  3. Tape tracing paper over the flash to diffuse the light.
  4. Have the subject look away from the camera.
  5. Use image editor to remove red-eye.