Photography is not a field that is accustomed to fast changes. Single-lens reflex cameras have been used in photography since 1861, and modern forms capture images using the exactly the same philosophy as they did back then. Improvements in film chemistry, and automation of elements like exposure metering and focus have been the largest advances. In 1975, Kodak created a prototype digital camera (using a digital sensor to capture an image), but not until the 1990s did these cameras reach the public.
The first digital SLR to market, the Kodak DCS 100, was a modified Nikon F3 (film) camera with a 1.3 megapixel CCD. The camera, which needed to be physically connected to a computer via a SCSI cable, had a retail price of $20,000. The subsequent iteration, in 1992, worked on reducing the size of the digital additions while also adding a 80MB hard-drive allowing for untethered operation. When the DCS 400 series was released in 1994, digital cameras were a serious option many users with financial means, such as large news organizations. The DCS 460 came with an astounding 6.2MP sensor, and variants of the DCS 400 series were made for the Associated Press (NC2000) and military (DCS 425). At its release in March of 1995, the DCS 460 listed for $35,600, or $175.35 per pixel. Later in 1995, Kodak also released the DCS 3 (1.3MP) and DCS 1 (6MP) based on the Canon EOS-1N, and utilizing the Canon EF mount.
Kodak was not the only company making digital versions of Nikon film cameras in the late 1990s. A partnership between Nikon and Fuji resulted in the Nikon E (or Fujix DS) line of cameras. Starting in 1995, the Nikon E2 (about $10,000) had a ⅔" CCD—about 28% the size of a normal sensor—but had an innovative "reduction optics system" that kept the standard 35mm field of view. The E2 shot at one frame-per-second, but its sibling the E2s could shoot three frames-per-second for seven shots.