Understanding Digital Camera : Image File Types

There are only three file formats you have to be familiar with when processing images: JPEG, TIFF, and Raw.

JPEG -  Joint Photographic Expert Group

You’ve probably already heard of JPEGs because they’re used on the Internet and for e-mailing images. If you’ve downloaded digital photos from your camera to your computer and saved them, you’ve probably seen the file extension ".jpg". JPEGs have their pluses and minuses:

 Pros

• Good for sending images over the Web.
• Easily compressed; can be saved as small files onto your hard drive.

 Cons

• Degrade (lose image quality) each time they’re compressed and  transferred. Compression reduces the file size at the expense of discarding information about the image itself. 
• Not the best format for printing gallery-quality prints.

The higher-resolution JPEG format is fine for sending images to editors of newspapers for publication as long as the images haven’t been compressed (opened and saved in an image processing program) multiple times. If you must use the JPEG file format and you want to maintain the highest image quality possible, always use the maximum Quality setting on your camera and in your software.

TIFF

The file from which you produce your output is a TIFF file. TIFF means Tagged Image File Format, which is a format that can be read on both Macs and PCs.

• You produce a TIFF file in a graphics or photo editing program like Photoshop.
• TIFF files cannot be viewed in Web browsers or on the Internet, but the file format does an excellent job of preserving image quality.

RAW

On many midrange and high-end digital cameras, you can save photos in Raw format instead of the traditional JPEG. If you’ve noticed that your camera has this capability, use it. Here’s why: A Raw image is like a digital negative — the unprocessed image data that your camera sensor captures. Raw isn’t an acronym; it just means that the image file itself is unadulterated — that is, it’s in a raw state. This untouched (um, raw) state is optimal because you can do your own processing later on your computer.

Different camera manufacturers use different file formats for their own versions of Raw. For example, you might see such file extensions as .nef (Nikon), .crw and .cr2 (Canon), .mrw (Minolta), .raf (Fujifilm), .orf (Olympus), .srf (Sony), and the less-common .x3f (Sigma and Polaroid) and .mos (Leaf).

When you save a Raw file, the camera creates a header file containing all the camera settings, including (depending on the camera) date/time captured, the camera used, exposure, ISO, lens, aperture, flash (if any), sharpening level, contrast and saturation settings, color temperature/white balance, and so on — in total, the metadata. When you then tweak a copy of your original Raw file, and process copies, you always leave the original image intact. Very cool. To top that, many camera settings (such as white balance and color adjustments) captured in a Raw file can be undone via special software. 

The downside to Raw is that Raw formats differ between camera manufacturers and even between cameras from the same manufacturer. Thus, you have to use proprietary software from that company or an image editing program such as Photoshop or Photoshop Elements. And because Raw files inherently contain more data, they take longer to open and process than a JPEG or a TIFF file. The Adobe Web site (www.adobe.com) has the software plug-ins to open your camera’s Raw files in Photoshop or Photoshop Elements for editing and adjustment.

Still, the creative possibilities are very tempting. And, more and more thirdparty editing and software programs are becoming Raw-compatible with more and more camera models and brands.

• Digital cameras generate Raw files. These files are read by the software from the company that you bought your camera from or by an image editing program.
• Each camera processes Raw files differently. The software to read and convert Raw files to the standard high-resolution TIFF or PSD format is available from the camera manufacturer that produced the format; you need that software to download the files from your camera to your computer. Programs like iPhoto are able to read some models’ Raw format. There’s also third-party software (such as that available at www.iview-mutimedia.com) that can read most camera’s Raw formats.
• Raw files are generally the preferred file type for producing an art photograph with a digital camera. The reason for this is that they can be adjusted for color and tonality more efficiently and with better results than can JPEG or TIFF files.

Only some types of digital cameras have this setting (can capture Raw files) because it is very memory intensive. Look for file formats in the camera’s specifications and see whether Raw is listed. You’ll pay more for cameras that have this format, but prices are falling rapidly.

source : Digital Arts Photography for Dummies book


Related post :
Understanding Digital Camera : Basic of Digicam
Understanding Digital Camera : Type of Digicam
Digital vs Film Photography

Digital vs Film Photography

Digital versus Film
Characteristic	Digital	Film
Cost	No film costs, but high-end equipment is expensive.	Film and developing costs. Forcheaper costs, develop as negatives only and scan at home.
Ease of use	More controls in LCD panel in addition to filmlike creative and manual modes controlled by knob at top of camera on most models. Frequent change of batteries or battery removal and recharging required for camera to work.	Fewer controls and no LCD make camera less confusing.
Image quality	Clear and vivid. Some folks notice a “plastic” quality that digital images can have. Edges are crisp (too crisp, according to some).	More natural-looking images when light hits film, which creates observable chemical change that’s recorded on the film and that can be kept as a hard copy for decades.
Output tools	Gallery-quality prints can be made at home with new multiple ink cartridge printers.	Gallery-quality prints have to be sent out for processing unless you have complicated developing materials at home along with a darkroom.

source : Digital Arts Photography for Dummies book

Understanding Digital Camera : Basic of Digicam

IMAGE SENSOR

At the heart of every digital camera is a light-sensitive silicon chip called a sensor, to gather the image data, whereas a traditional camera exposes light to emulsion film. The sensor takes the place of film for recording images.

SENSOR TYPE

Sensor is the electronic chip that records the image in a digital camera. They come in two main types : 

CCD (Charge-Coupled Device)

CCDs are used almost exclusively in compact cameras. This is a light sensitive chip used in your digital camera for image gathering. The CCD Pixels gather the colour from the light and pass it to the shift register for storage. CCD's are analogue sensors, the digitising occurs when the electrons are passed through the A to D converter. This "Analogue to Digital" converter converts the analogue signal to a digital file or signal.

CCD Sensor in compact digicam

CMOS (Complementary Metal Oxide Semiconductor) 

CMOSs are used in larger, and more expensive DSLRs. These produce lower amounts of power consumption, but are not as popular as the CCD sensors used in most digital SLR's. (To see the detail comparison of CCD vs CMOS click here)

 CMOS sensor in DSLR

There are other types, but not well used, JFET (Junction Field Effect Transistor) – developed by Nikon and used in a very small number of their cameras and X3– a new type of sensor developed by Foveon that used only in Sigma DSLRs and a couple of Polaroid compact cameras. 

SENSOR SIZE

Camera sensors come in a variety of sizes, the smallest are used in compact cameras. Bigger sensor is better.

There are some "size type" of sensor :

• Full frame 35mm (36mm x 24mm sensor size) used on Full Frame DSLR
• APS-H (Advanced Photo System type-H) with 29mm x 19mm sensor size, used by CANON
• APS-C (Advanced Photo System type-C), with +/- 22mm x 15mm sensor size used on most DSLR
• Four Thirds or 4/3 (17mm x 13mm) used on most mirrorless digicam
• Compact sensors : 1/2.5" (5.7mm x 4.3 mm), 1/1.8" (7.2mm x 5.3mm), 2/3" (11mm x 8.8mm) used in compact digicam, phone camera, web cam, etc.

Most digital SLRs use larger sensors than the average compact camera. A good rule of thumb is that the larger the size of the sensor, the bigger each light-collecting pixel can be and the more light it can record without the need to have the signal over amplified. The result of these bigger pixels is a lovely sharp, clean image that doesn't suffer from graininess when setting the camera at higher ISO or sensitivity levels. At top end of the market, digital SLRS have either APS-C (or DX-sized sensors) or full-frame chips, which are the same size as the image area on an old-school piece of 35mm film. These really large sensors have both a high resolution and large pixels, which means they can record high-quality images even at high ISO sensitivities. These sort of images can be reproduced at very large sizes while maintaining really high quality.

SENSOR RESOLUTION or MEGAPIXEL

The quality of any digital image, whether printed or displayed on a screen, depends on its resolution, or the number of pixels used to create the image. Megapixel (MP) relates to the number of pixels per unit length of image. Bigger megapixel is better in cropping work or large printing.

6 MP   : 12 x 18 inci
10 MP : 16 x 24 inci
16 MP : 20 x 30 inci
24 MP : 24 x 36 inci

CAMERA LENS

Apperture Value or f-number
The aperture range of a lens refers to the amount that the lens can open up or close down to let in more or less light, respectively. Apertures are listed in terms of f-numbers, which quantitatively describe relative light-gathering are.

An f-number of X may also be displayed as 1:X (instead of f/X), as shown below for the Canon 70-200 f/2.8 lens (whose box is also shown above and lists f/2.8).

 

Focal Length

The lens' focal length determines the magnification of the image projected onto the image plane. Focal lengths are usually specified in millimetres (mm), but older lenses might be marked in centimetres (cm) or inches.

Types of Lens

Prime Lens

The opposite of a zoom lens, prime lenses have one fixed focal length. They represent the best quality of lens available, but have the big drawback in that they cannot 'zoom in' to a subject.

Prime Lens of Canon DSLR and Pentax-Q 

Pancake Lens

A pancake lens is colloquial term for a flat, thin lens (short barrel), generally a normal or slightly wide prime lens for a camera. 

Pancake Lens and attached on DSLR

Aspherical Lens

A lens with edges flattened so that it is not a perfect sphere. These produce a much superior image.

 Aspherical Lens

Spherical/Conventional vs Aspherical Lens

Wide Angle Lens

The focal length that gives you the widest angle of view. I.e. 10mm, 16mm, 24mm etc.

Canon wide angle lens  (17 - 40mm)

Zoom Lens or Telephoto Lens

A variable focal length lens. The most common on digicams has a 3:1 ratio (i.e. 35-105mm). Detachable zoom lenses include for example, 24-70mm, 70-200mm and 100-400mm

Canon Telephoto Lenses

Macro Lens

These lenses are used for close up photography. The have similar properties to a normal lens, but they are able to focus a lot closer to the subject. Common focal lengths are 50/55mm or 90/100/105mm. The lenses with the longer focal lengths come in very handy for taking close ups of subjects that might otherwise be scared away. The optical quality of a macro lens is normally very high. 

 

 Macro Lens

 

  Fly Macro Lens Photo Shoot*

(*see others macro shoot at www.smashingmagazine.com)

Fisheye Lens

A Fisheye Lens looks surprisingly enough like a fisheye. Their angle of view is a full 180%. There is a trade off in that the pictures produced are distorted in that the centre of the picture almost comes out to meet you whereas the top, bottom and sides of the picture appear to be further away. You can buy both circular and full frame fisheye lenses with full frame being the most common. 

 Macro Lens and Photo Shoot

AUTOFOCUS

All digicams and most modern SLR lenses have this function now. The only difference is that with an SLR you can normally select manual focus if necessary. The lens automatically focuses on the subject as quick as the eye. The lens on the camera focuses automatically when the shutter is half pressed. The viewfinder normally has focussing points shown to assist the user in knowing what will be in focus. 

Focus Assist

Cameras with this send out a light, either normal or infra red to light up the subject to assist with the autofocus in low light or darkness. 

Focus Lock

Focus lock means pre-focussing the subject and re-framing by moving the camera. This is done by half pressing the shutter to focus and fully pressing to expose. Done to ensure crisp, sharp eyes for example.

Multi-Point Focusing

The autofocus systems uses several different portions of the image to determine the correct focus.

Multi Zone Focusing

Many digital cameras now offer multi zone focusing. The camera will automatically determine which zone (centre, left, right, upper or lower) to use to perform the auto focusing. You no longer have to make sure that your subject is in the centre of the viewfinder in order to be correctly focused.

EXPOSURE

Exposure is amount of light that hits the image sensor of film controlled by the shutter speed and aperture.

AE - Auto Exposure
The camera sets the shutter speed and aperture for the correct exposure according to the light. When the camera is set to this mode, it will automatically set all the required modes for the light conditions. I.e. Shutter speed, aperture and white balance. The 3 types are:

1. Program Mode : The camera will choose the shutter speed and aperture automatically, effectively making your SLR a "point-and-shoot". It will normally assign a shutter speed of 60th of a second or higher if possible.
2. Aperture Priority : You choose the aperture setting and the camera will automatically choose the shutter speed according to the lighting conditions. Best setting for controlling the depth of field.
3. Shutter Priority : You choose the shutter speed and the camera will select the correct aperture as long as there is enough light. Good for sports or action photography where you need control over the shutter speeds.

AE Lock

This enables you to lock the current exposure reading and re-frame the shot using the same setting. A half-press of the shutter is normally required to activate this function, fully pressing only when you want to capture the image.

Exposure Bracketing

Camera will take 3 or 5 images and varies the exposure up or down for each photograph ensuring at least one will be well exposed. 

Exposure Compensation

You can lighten or darken the image by under or over exposing the image. (EV compensation).

Over-exposure

This is an image that appears much too bright. The highlights and colours are totally lost and usually unrecoverable even by top software. Either the shutter speed was too long or the aperture was too wide.

SHUTTER