Posted by
digibatt on Tuesday, May 26, 2009 4:51:50 AM
A digital camera uses and/or contains random access memory (RAM) to store the images. When RAM is used up, it should be restored in order to take more pictures. There are currently several types of storage media used to record digital photos. The most common ones are Smart Media, Compact Flash, and Stick Memory. Also available is another card-sized storage media, an IBM “Microdrive”, which fits the Compact Flash Type II card slot and can store up to 1 gigabyte of data when used with a compatible camera. Regardless of the storage media used by the camera, pictures can be downloaded and stored either on the computer’s hard drive or on a compact disk (CD) if the computer is equipped with a CD “burner”.
The number of photos which can be taken per session is a function of the resolution selected and the amount of memory required.
Another file type in which some data may be lost is known as a “lossy” file. Images stored this way take up less much less room but may lose some data or image quality. However, the resultant “loss” may not be significant to over-all picture quality. One type of “lossy” file format that is currently used by most digital cameras is a standard file format known as JPEG (Joint Photographic Experts Group). This file format is designed to address the known limitations of the human eye and was named for the committee that devised and wrote the standard. At the highest JPEG resolution, even though there may be some small loss of image quality, it would not be obvious to the human eye. (This is less true for pictures of things like signs or other very hard-edged objects). When the camera saves files in the JPEG format, the amount of compression (image quality) must be decided upon. Most cameras give you the option in the setup menu to choose the JPEG image quality: fine (1:4 compression ratio), normal (1:8 compression ratio), and basic (1:16 compression ratio). The decision is always a compromise between image quality and the number of files that can be fit on a memory card. Unless many images need to be crammed onto the card, or the final quality is not that crucial, it is recommended to always use the camera setting that delivers the highest quality (lowest compression level).
Because they are electronic, digital cameras require significantly more power than other types. As a result, batteries can drain quickly. This can be true even when batteries are left in the camera and are not in use. Repeated viewing of images through the camera’s liquid crystal display (LCD) screen can also rapidly deplete batteries. This is particularly significant for digital cameras because battery depletion can cause the camera settings to be lost, in addition to being problematic if the power suddenly disappears when needed during use.
Most digital cameras use nickel metal hydride (NiMH rechargeable batteries) others use nickel cadmium (NiCd, rechargeable), lithium (non-rechargeable), and of course, alkaline (nonrechargeable). Of these, the NiMH batteries are the most economical because of their basic cost, rechargeability, length of charge, and long service life.
Images stored to a CD-R are created by permanently altering the disc with a laser light beam. CD writers cannot delete laser marks, so the images can be stored without alteration and any alteration would be detectable. This is only true for CDR, not CD-RW (read-write). The “original” images could be stored this way to form an unalterable archive and it is feasible to store large numbers of images in a small amount of space (a typical CD can store hundreds of images). Once the images are archived to a CD-R, copies of the unaltered “originals” can be made from the CD-R and any necessary enhancements, such as improving contrast or “cropping” can be done on the copies and properly noted in a Photo-Log for future reference.