Photography - Understanding Digital Image Formats
Images manufactured by digital cameras now rival the grade of our finest photographic film stocks. But the nature of a digital image shares almost nothing in common with the analog image captured in a film emulsion.images
An image captured in film can be an incredibly complex physical object that features a life of its own, and is interpreted directly by inspection using the human eye. A digital image, alternatively, is an electronic representation of a scene - a string of numbers specifying red, green, and blue light intensities that requires some form of software to render it into a visual form that may be displayed on a suitable imaging device, being a photo-printer.
When an image is captured digitally, it's done with a mosaic of light-sensitive electronic pixels. These pixels are in fact independent square-shaped photodiodes which are arranged by means of a large tiled surface. Well, large in the point of view of a single pixel, since if we were to enlarge the pixel on the size of a kitchen porcelain tile, then the area taught in entire image sensor could be about the same as exactly what a football stadium.
A standard medium-resolution digital camera might have about 4000 electronic pixels arrayed along one regarding its image sensor, leading to 2500 along the other, making for around 10 million pixels overall. The look sensor in this case can be said to have a 10 megapixel resolution.
Now, when a picture is recorded electronically, what each pixel around the sensor measures could be the amount of energy the sunshine imparts to it during the photographic exposure. Or perhaps simpler terms, the brightness in the light. This large array of numbers is known as the RAW format from the image. It is, in place, the digital equivalent of the video negative (or positive in the matter of slide film), mainly because it carries ALL the information linked to the exposure.
As it happens, you cannot simply interpret these RAW image records in the color-by-the-numbers type fashion. If you were to assign the color and brightness of each and every pixel to a corresponding printed pixel on a piece of photographic paper, or with a computer screen, you would not go to a pleasing representation from the scene that was photographed.
The real reason for this is that the way our eyes react to color brightness is different than the way electronic pixels respond to it. Our eyes are less tuned in to large changes in brightness than are electronic pixels. The RAW numbers must be processed in a way that compensates with this difference.
What this means is that quite a few number crunching has to be performed to get the best derive from our RAW image before it is printed in any form. This can be done inside the camera if you wish to immediately see a preview of the result on your camera's Vast screen. Or it might be done using complex image processing software on your computer, once you have downloaded the style. Until then, the RAW image has to be stored for later use.
Unfortunately, inside the race to conquer the digital photography landscape, photographic camera manufacturers adopted a first-to-build is first-to-dominate philosophy and created their very own proprietary versions from the RAW image format. A Canon RAW image, therefore, is formatted differently compared to a Nikon RAW image for your exact same image. Due to the proliferation of RAW formats, image processing software now has to cope with hundreds of competing RAW image formats. In practice this is just not possible, which means that your imaging processing software (whether it comes from a vendor besides your camera manufacturer) will probably support only the major RAW formats, such as Nikon's NEF format, Canon's CR2 format, and Fuji's RAF format.
This case is likely to improve with time, however. Adobe has entered a digital imaging fray by publishing a standard for a RAW image format it calls Digital Negative, or DNG. Slowly, camera manufacturers, like Hasselblad, Leica, Ricoh, and Samsung are building DNG support to their cameras, and with luck the larger players in the field will observe suit.
What this means, if a standard such as DNG is adopted, is the fact that when a photographer captures a graphic, stores it in RAW format, then forgets about it for Ten years, they won't discover, when they get around to retrieving it again, that their image format has become obsoleted and there is no longer any software that could render the file in to a viewable and printable image. For big corporations with millions of archived images to preserve, this sort of problem represents a logistic nightmare, which is very costly to stay on the top it.
In the long run, a standardized RAW format will guarantee archival integrity of images, reduce headaches for unwary photographers the world over, and save them both time and money. DNG support is now available in Adobe software packages including Photoshop, and Photoshop Elements, and can likely migrate to third party image software packages as the standard is embraced. Adobe now offers a free Digital Negative Converter by reviewing the site which allows forward-thinking photographers to change their existing RAW image format files into a DNG version as well.
As continues to be mentioned, software is had to convert a RAW format image into one that can be displayed and printed. This can be analogous to the "development" process for negative film. The most typical image display format is JPEG (which means Joint Photographic Experts Group). The JPEG format is but one that can support a lot of compression, so that the final viewable image is substantially smaller in size (number of bytes) than the RAW image file. Therefore it can be sent on to others easily, via email for instance. The JPEG format is also an industry standard image format, so the file can be opened and browse by all commercial image processing software plus a large number of open source image software products.
Another standard image format is TIFF. However, TIFF file sizes are generally much larger than those for the equivalent JPEG image, in order that they are used mostly by pros who need to produce large print reproductions rich in resolution. In fact, the DNG standard is based on a version of TIFF.
Various image processing algorithms are placed on RAW images to convert them into printable form. This consists of performing white balancing, which is means by which an unwanted overall color cast is taken away from the image. When a color cast is present, a photographed all-white object will render with the off-white component that subtracts from image fidelity. The RAW image stored through your digital camera will likely possess a record of the white balancing correction used when the image was created, but they're free to adjust this when editing the image derived from the RAW format.
You should appreciate that when you are trying to the create the best possible printable image, you'll want to start with the original RAW image file. Each printable version has been made, such as a JPEG version, the applied image processing algorithms have "tossed out" a lot of image information that was deemed unnecessary. These lossy operations are irreversible, and they also limit your remaining alternatives for tinkering with the image in case you decide that the result is less than what you are after. The solution is to return to the RAW format file and commence over.
Because the differences in file sizes are really great, if you are not focused on collecting RAW image files and processing them for the perfect image at a later date, you should consider allowing your camera to create JPEG images since the default, and overlook the RAW format altogether. This can improve the responsiveness of one's camera, because you don't need to store the large RAW images for your memory card. If, for instance, you are photographing a ball game, your frame-rate when shooting in the continuous mode is going to be greatly improved. Also, it will be possible to record a much higher number of images in your memory card before it fills up.
On the other hand, if you will be photographing something of importance, do consider the implications of not while using the RAW format to record your images. You might regret it later.