CHOOSING A DIGITAL CAMERA

Senior Center, Inc. Computer Club Meeting 9-11-06

Whitman "Pete" Cross

 

A - FEATURES FOUND ON DIGITAL CAMERAS

FORMAT SIZE / SHAPE COMPARED TO 35 MM FILM:

This is the single most noticeable difference to many folks; the length/width ratio( called the "aspect ratio") of the image is not the same as in 35mm format. Also the sensor is smaller than 35 mm. so that a smaller part of the lens is used, resulting in the slight magnification of the image. For most digital cameras, the magnification is roughly 1:1.5, meaning that a 50mm. lens (normal lens in a 35mm. camera) when placed on a digital camera will act like a 75mm. lens (slightly telephoto). Thus, to get truly wide angle images in digital cameras, it has been necessary to design lens especially for digital cameras.

Be careful when ordering prints: determine how much of original image will be cut off to produce the print size you want!! (In 35mm, 5x7 produces exact image; 8x10 will cut off some of the length of original image).


CAMERA SIZE & SHAPE:

Does shape fit your hand well? Are you going to be carrying it in a pocket or purse or knocking around in your car?

How fast do you want to take a picture when you pick up camera (what is the "start-up time" & "lag time"?)

Bigger and more weight makes it easier to frame image and hold camera steady.

There is a definite place for the shirt pocket camera!

Critical question: How thick can your camera be? A longer zoom requires much more thickness.

 

PIXELS:

A "pixel" is a picture element: the smallest area of color information that can be detected by a digital imaging sensor. The larger the sensor, the more pixels and the higher the resolution (sharpness). Cameras are often rated by "megapixels" or millions of pixels. Not as important today since nearly all cameras have at least 5 megapixels capability.

 

FORMATTING & COMPRESSION:

"JPEG" is the most common type of formatting used, but it compresses the digital information a little or a lot, depending on how you set the camera. A lot of compression allows you to place many more images on one memory card, but this action will also reduce the size of acceptable prints you might want to make.

If you plan to use the computer to work over your images, then you may want a camera that offers a number of formatting selections such as RAW (no compression) that produce very large files (you can get only 1/3 as many images on a card as with low compression JPEGs.), but you can do more manipulation and produce larger prints.

 

TYPE OF BATTERY:

Do you prefer using AA rechargeable or throw-aways….or do you prefer a dedicated cell you place in a charging unit? (this type holds its charge longer, but cost more)


START-UP TIME:

The cheaper cameras have longer start-up times. This the time it takes for the camera to be ready to take a picture after you turn it on.


SHUTTER’S LAG TIME:

This is the time from when you push the shutter button to the actual recording of the image on the memory card.

When you press the shutter, the following steps happen before image is on the card:

- light meter reads the scene and adjusts the shutter and the size of the aperture

- the lens is focused on part of the scene

- the shutter opens

- the image arrives at a buffer (temporary storage) that quickly passes image on to memory card. However, if you were to shoot a TV sequence or use continuous shooting mode, the buffer can hold only a limited number of images at a time if you were to utilize continuous shooting mode that takes a sequence of photos very fast until buffer is full.

- the image is transferred from the buffer to the memory card

- a signal is given that it is OK to take a second picture.

Lag time can seriously interfere with capturing sports action and those instantaneous baby expressions!
This lag time is almost non-existent for professional SLRs that cost over $1,500.

 

VIEW FINDER:

Generally shows less than whole image seen on the LCD screen. Many ’06 cameras have no viewfinders, relying entirely on brighter LCD screen.

 

SIZE OF LCD SCREEN:

The LCD (liquid crystal display) screen can be as small as less than 2 inches left to right. However, a much larger and brighter screen, up to 3 inches wide, is common on most cameras introduced in 2006. Be careful that the screen is not so big that the back of the camera is little more than a screen. Such cameras must place buttons elsewhere, often in less than ideal situations.

 

SIZE OF SENSOR:

The larger the sensor, the more information it can record from the image and the less "noise" will be produced as the ISO is increased (as the sensor is made more sensitive so it can record images in much lower ligiht)

 

AMOUNT OF ZOOM:

The range in telephoto capability is expressed in the number of times a lens can magnify a normal image. Thus, a 4X zoom can magnify an image 4 times the widest setting. The longest zoom capabilities today are about 12 X.

Zoom capabilities are expressed in two ways:

a- optical zoom: the range of magnification resulting from the actual movement of the lens; this yields the highest quality images.

b- digital zoom: additional magnification of an image can take place beyond that of the optical capabilities by magnifying the image on the sensor. This is similar to magnifying a portion of a photography print to blow it up larger. All the imperfections are also magnified and the image looses resolution, sharpness, contrast, and color intensity. However, recent developments in digital cameras have improved the quality of images coming from a conservative amount of digital zooming. "It is often better to have a lower quality print of a bird highly magnified than to miss getting any picture of the bird!"

 

IMAGE STABILIZATION (IS):

First appeared less than ten years ago in 35mm telephoto lenses. A motor in the lens acts as a gyroscope offsetting the movement of a hand-held camera so that a sharp image can result from using a much slower shutter speed than was possible earlier. (Example: until IS was invented, the guideline read: "Use a shutter speed that is the reciprocal of the focal length of the lens". This means that when using, for example, a 300 mm. lens, it is advisable to use a shutter speed that is the reciprocal of 300 = 1/300 sec. in order to get a sharp image.

Today, with IS, it is possible to obtain just as sharp an image using a much slower shutter speed, such as 1/40th sec.

This then allows one to take long telephoto shots under much lower light levels.

Recently, image stabilization has been placed within the camera so, in the case of SLRs, it is not necessary to use as heavy or expensive a lens as before. The sensor actually responds to any unwanted motion. This first appeared in the higher end P & S cameras a year or two ago.

 

MAXIMUM & MINIMUM APERTURE SIZE:

The higher the quality glass used in constructing a lens, the faster light can be transmitted. However, the ability to gather light quickly is most affected by the maximum size of the lens aperture. The size of this opening is described in "f-stops". F/2.0, 2.8, 4.0, 5.6, 8, 11, 16, 22, etc.. Starting with the smallest value (lets in the most light), each of these numbers lets in twice as much light in a give time as the next higher number.

To let in more light, a lens must be larger, heavier, and cost more. To keep prices, weight, and size down, zoom lenses commonly have a wider max. opening at the wide angle position than at the fullest telephoto position. These numbers are important to note when looking at a camera. If you are going to be using the telephoto positions a lot, try to find the lowest f/stop number in the telephoto position. This is one reason folks turn to SLR cameras so they can purchase special lenses. Example: A zoom lens covering 80-200mm with f/stops ranging from 3.5 to 5.6 can be purchased for a few hundred dollars. A similar range zoom that remains f/2.8 throughout its range will cost around $1500. because the glass must be so much bigger to maintain the same f/stop at telephoto settings.

 

RANGE OF SHUTTER SPEEDS:

Shutter speeds may vary from many seconds in length to 1/2000+ sec.. Generally a good rule of thumb to follow is the same that cameras follow when set on automatic or program: Do not try to hand-hold a camera that is using less than 1/100 sec. exposure unless you are practiced. Many digital cameras make flash go off if shutter speed is lower.


ISO (light sensitivity) RANGE:

ISO refers to the film or sensor’s sensitivity to light; the higher the ISO, the more sensitive is the sensor or film.

With film cameras, using higher ISO numbers may produce "grain"or mottling; with digital cameras, the effect is termed: "noise" and is seen as a mottling or grain in the dark, smooth areas of a photograph.

Common ISO #s producing sharpest images: 50, 100, 200. Today, 400 is noise-free in many cameras, but ISO #s may go up to 1,600 or even 3,200 where you will see a lot of noise. However, there is software available to remove much of the noise through computer manipulation.

This is probably one of the most important advantages of digital vs. film: ability to change ISO at will; in film cameras, ISO can only be set once for the entire roll.

 

LIGHT METER CAPABILITIES:

1- Matrix (image is divided into a no. of segments, each producing a different reading; meter then averages all the readings to produce the best overall setting for that scene)

2- Center-weighted (most of reading is from within a circle seen in viewfinder

3- Spot (small circle in center of viewfinder produces the setting)


IN-CAMERA FLASH:

- Range of flash:

- at ISO of 100: seldom more than 10 ft.
- at ISO of 400: might reach 20 ft. depending on wall/ceiling color and closeness to camera.

- Fill-flash: - You can reduce power of flash so there is just enough light produced to fill in shadow areas.

 

TYPES OF SETTINGS FOUND ON DIALS:

- Automatic

- Program

- Manual

- Landscape

- Portrait

- Close-up

- Nightscape

- Nightscape with flash

- Aperture-priority

- Shutter-priority


TAKING CARE OF YOUR CAMERA:

- Not built to withstand hard banging and dropping; plastic cases can crack; high-end cameras can withstand more serious trauma. (Is lens mount on SLR plastic, aluminum, or steel?) Circuit boards can withstand more than mechanical parts of camera.

- Remove face grease and salt spray frequently. Keep viewfinder and LCD screen clean.

- Can stand higher levels of temperature than film; at TEMP below freezing, battery life is cut in half at least.


ACCESSORIES – to think about:

- Extra batteries: In winter, keep them near your body for warmth. Zooming lens in and out as well as frequent use of flash will use a lot of power.

- Extra memory cards: No. of pix on a card depends on card capacity, size of sensor, and no. of megapixels, and. resolution chosen.

- Lens cleaning: (a) microfiber cloths; (b) Zeiss lens paper (Sam’)

- Sensor cleaning on SLR cameras: hand air blaster or special brush or pay technician at camera store to do it.

- Camera case:

- Camera strap:

- Tripod or bean bag:

- Reflector or flash-fill: To eliminate harsh shadows mid-day on faces or flowers.

- Accessory shoe on camera: To attach separate flash or a level (used to keep horizon level)

- Separate flash unit:

B - WHAT DO YOU GET FOR YOUR MONEY?

The competition among manufacturers of digital cameras is so keen for your dollar that, every six months, you have an improved product at the same price (or the same product for less cost).

POINT AND SHOOT / NON-REMOVABLE LENS:

LESS THAN $350.:

- Noticeable lag time between pressing shutter button and picture being taken and saved on card.

- May not have viewfinder to look through.

- Small; more difficult to hold steady.

- No manual controls of shutter and aperture

- Small sensor

- Less than 6 megapixels (not important if prints less than 11 x 14 are anticipated)

- Fewer dials and buttons; many options accessed through menus that are read on LCD screen.

- Brightness of LCD screen minimal; very difficult to take pictures in bright sun.

$350 - $700:

- May have "image stabilization" that permits sharper pictures at slower shutter speeds.

- Larger and brighter LCD screen.

- More button-operated options / features

- Use of higher ISO (requiring less light) without "noise"(graininess in dark areas of photo)

- Swivel LCD screen on some models permits getting unique angles of shots by placing camera on ground or overhead and still being able to see screen clearly.

$700-$1,000:

- A larger camera with a larger sensor, a larger aperture lens (lets in more light) and a longer optical zoom capability.


SINGLE LENS REFLEX (SLR):

- permit the use of many, many different types of lenses.

- CON: Removable lenses allows dust to be attracted to the sensor’s surface; very delicate cleaning required; however, manufacturers are now adding in self-cleaning features.

- SLR cameras will vary in weight and size; lenses may be the heavy part of the package, often requiring tripods.

- Image Stabilization may be in camera body, but more likely within each lens.

- Have much larger sensors; one model has a sensor the size of a 35mm. negative!


C – QUESTIONS TO ASK YOURSELF BEFORE BUYING A CAMERA

1- What types of photos do I plan to take?

2- How high a priority is:

3- What will be required of camera to produce the kind of photo you want?

(sports; people; flash/night shots; indoors vs. outdoors; nature; birds; close- ups; need for slight or very long telephoto capabilities; etc.)

4- What do I plan to do with the images after placing them on a memory card?