Digital photography

Digital photography is photography using a camera that uses an electronic sensor to record the image as a piece of electronic data rather than as chemical changes on a photographic film. The sensor is either a light sensitive CCD, or a CMOS semiconductor device. A digital memory device (usually flash memory; floppy disks and CD-RWs are less common) is usually used for storing images, which may then be transferred to a computer later.

The advantages of this method over traditional film include the greatly reduced cost per image, the potential to make taken images instantly available for appraisal, the greater number of images that can be conveniently transported, and the removal of the requirement to develop the film in a photo lab. In addition, digital cameras can be smaller and lighter than film cameras.

Recent digital cameras from leading manufacturers such as Nikon and Canon have promoted the adoption of digital Single-lens reflex cameras (SLRs) by photojournalists. Images captured at 2+ megapixels are deemed to be of sufficient quality for small images in newspaper or magazine reproduction. Six megapixel images, found in modern digital SLRs, when combined with high-end lenses can match or even exceed the detail of film prints taken with 35 mm film based SLRs, and the latest 12-megapixel models can produce astoundingly detailed images better than almost all 35mm images.

The number of pixels n for a given maximum resolution (w horizontal pixels by h vertical pixels) can be found using the formula: n = wh. This yields e. g. 1.92 megapixels for an image of 1600x1200.

The theoretical maximum resolution of a camera (w horizontal pixels by h vertical pixels) providing n pixels total can be computed following the formulas

and

for the width of the resulting image (assuming the ratio of width to height is 4:3). These can be derived from the above formula n = wh.

With the acceptable image quality and the other advantages of digital photography (particularly the time pressures, of vital importance to daily newspapers) an increasing number of professional news photographers use these devices.

It has also been adopted by many amateur snapshot photographers, who take advantage of the convenience of the form when sending images by email and to place on the World Wide Web.

In late 2002, 2 megapixel cameras were available for less than $100 and some 1 megapixel cameras were under $60. At the same time, many discount stores with photo labs introduced a "digital front end," allowing consumers to obtain true chemical prints (as opposed to ink-jet prints) in an hour. These prices competed with prints from negatives.

But the general public still purchased far more single-use film cameras than digital models.

Some commercial photographers, and some amateurs interested in artistic photography, tend to avoid digital photography at this stage, as they believe that the image quality available from a digital camera of a given price is still inferior to that available from a film camera, and the quality of images taken on medium format film is near-impossible to match at any price with a digital camera. Some have expressed a concern that changing computer technology may make digital photographs inaccessible in the future while printed images have a very long lifespan.

Digital photography was used in astronomy long before its use by the general public and had almost completely displaced photographic plates by the early-1980's. Not only are CCD's more sensitive to light than plates, but the information can be downloaded onto a computer for data analysis. The CCD's used in astronomy are similar to those used by the general public, but are cooled to liquid nitrogen temperatures so as to reduce the noise which is caused by heat.

Other commercial photographers, and many amateurs, have enthusiastically embraced digital photography, as they believe that its flexibility and lower long-term costs outweigh its initial price disadvantages. Let's examine cost comparisons. All costs for the following are expressed in US Dollars (US$).

In December 1993, single-use cameras sold in the Washington, DC area for around US$8 for 24 prints. Developing can be obtained for around $4 at certain grocery and drug stores. This sets the approximate retail price per picture at approximately $0.50 per photograph using single-use cameras.

If one is using a standard film camera, roll film in 200 speed for a 35MM camera is around $4 for 24 prints, with the developing about the same as noted above, making the approximate retail price per picture at $0.30, not including the cost of the film camera, which is probably about the same as a digital camera.

Flash memory chips can be purchased for around $20 for 64 megabytes of memory. JPEG images as stored use approximately 420,000 bytes each for 1600x1200 pixel images, which means that one flash chip can hold approximately 128 images. (If smaller sized images are selected, more can be stored on the flash memory.) Images can be transferred off of the flash chip - meaning it can be emptied and reused many times, the estimates are anything from 1,000 to 10,000 to a million times - using a common media reader, which sells for about $20. Images can be copied onto a computer's hard drive or CD-ROM or CD-RW disc. Many computers already have CD writer drives so the cost is not included, but can be purchased for around $50. A CD-ROM disc sells for less than $1, and can hold about 1200 photographs of the above size. This makes the cost (not including the camera) for digital photography to be $20 for the extra flash memory, $20 for the flash memory reader, $1 for the CD, which means the cost for storing the first 1200 digital images is US$41, or US$0.04 each, and $1 for the CD for each additional 1200 images. In bulk, a spindle of 100 CDs can be purchased for approximately $20 or less.

In summary, for approximately the cost of 85 film images, one can store 128 digital images without needing to copy any to CD, or one can store 1200 images on CD if one keeps moving and erasing the images off the flash memory as it becomes full. If we include the additional cost of a CD writer, the break-even point for digital over film is 230 film images; at which point the next 1000 digital images cost zero, and the next 1200 cost $1. Adding in the purchase price of a spindle of CDs, for the same amount of money, one may make approximately 300 film images, or may store a whopping 120,000 digital ones.

Almost all of the cost of digital photography is capital cost, meaning that the cost is for the equipment needed to store and copy the images, and once purchased requires virtually no further expense outlay. Film photography requires continuous expenditure of (much higher amounts of) funds for supplies and developing.

For certain types of photographs such as time-lapse, extremely high resolution images, or where it may be necessary to prove non-change for evidentiary purposes, film photography is a much better choice. For most other photography, especially amateur images, digital imaging is probably adequate or more than sufficient, and considerably less expensive.

Exchangeable image file format (EXIF) is a set of file formats specified for use in digital cameras. This specifies the use of TIFF for the highest quality format and JPEG as a space-saving but lower quality format. Many low-end cameras can deliver only JPEG files. Another format that may be encountered is CCD-RAW, which is unstandardised.

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