Image Files
Image files from digital cameras comes in two types, RAW and JPEG. The RAW image is not processed and contains all the information each time a digital picture is taken. The JPEG file is processed raw information and can be used immediately upon removal from the camera. Most of the higher end cameras have RAW image files can also switch to JPEG, or a combination of RAW and JPEG each time a picture is taken. A detailed description of all the types of image files are list below RAW files contain all the information from the CMOS or CCD sensor when a photograph is taken. This is the same information that would be taken if film would have been used. One of the problems is that every manufacturer’s RAW information is different or not compatible with each other. To view the image in the computer, the information has to go through a converter, which is specific to the manufacturer of the camera used. Each software manufacturer will supply the proper converters. Some camera manufacturers will change the RAW information each time a new camera becomes available.
The advantages of using RAW are complete control of the image, from when it is in the camera to when it is in the computer. In the camera it would be like changing film, except a change can be made for each picture that is taken. White balance can be changed for any light condition. Once the file leaves the camera and is downloaded into the computer software, it is automatically converted to RGB. The files can now be corrected and manipulated any way the photographer desires, but the original RAW file can never be changed. If anything goes wrong or you don’t like what you have done, the original is still available.
The size of a RAW file is considerably larger than a JPEG file, which means fewer pictures for a memory card. It also takes longer to write a file, but many of these obstacles are being over come by larger and faster memory cards.
JPEG (Joint Photographic Expert Group) files are used in all point and shoot cameras. The files are small which means more photos per memory card. The JPEG file is compressed and processed in the camera, so when it is down loaded, it can be printed, sent over the internet, and shown on a monitor with out any additional processing. To get this small size, lossy compression is used, which discards some of the original information to reduce the size of the file. Some cameras use several levels of compression which is adjustable. Large quality prints will not be able to be made, and the information lost can never be recovered. Anytime a file is resaved in the computer, additional information is lost. The JPEG is very efficient for what it does, although it does have limitations. BMP is an uncompressed, proprietary format from Microsoft, and has no real value.
TIFF, Tagged Image File Format is a high quality image standard used by commercial and professionals photographers. It is lossless but the files are very large and can not be used on the internet. There are several compression formats that can be used with TIFF if needed. G3 is used for facsimile and line art. LZW is a lossless compression. TIFF is high quality format and is also very good for archiving.
GIF, Graphic Interchange Format is an 8 bit per pixel bitmap image format and uses 256 different RGB colors. This is not acceptable for photographs or anything with continuous color, but is perfect for simple images, graphics, and also supports animation. It has wide usage on the WWW since its inception in 1987.PSD, Photoshop Digital is an image file used in Photoshop. Its main purpose is working with layers and panoramas. Layers can be saved and brought back without any image loss, as there is no compression.
DNG, Digital Negative is a RAW file image format designed by Adobe. It is an attempt to bring together all the various RAW formats into one universal format.
These are the most common image formats that are in use today. Each has its own place in the photography industry, although as digital photography changes, there may become a need for a new format.
