The various names

Eastman Kodak itself refers to the DC210 in various ways. Digital Science (occasionally abbreviated to DS) sometimes comes after "Kodak", and Zoom is sometimes part of the name. Thus all of these are the same:

The newer DC210 Plus, marketed in the US and perhaps elsewhere, is black rather than silver and is subtly improved. For all I know, it may have a different fixed focus -- but the focus is fixed.

The DC210A, marketed in Japan, is also black. I suspect that it's a Japanese-language version of the DC210 rather than of the DC210 Plus. Again, although the focus may be fixed differently, it is fixed.

Same for the DC215, now sold in various pretty colors, but sadly unable to focus.

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Other offenders

It's not easy to see which other companies market fixed-focus digital cameras, as most aren't keen to admit that their products are badly flawed. However, it seems that Canon, Casio, Minolta, Nikon, Panasonic, Ricoh, Sharp, Toshiba, Umax and Yashica also sell them.

At least one of Sony's cameras appears to have a small number of focus settings -- inferior to either continuous manual focus or autofocus, but better than what Kodak provides for the DC210 -- of which one setting, between landscape and close-up, is called panfocus. This is also Kodak's Japanese-language euphemism for fixed-focus; it's another term that should set off alarm bells.

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Aperture is, in practice, a measure of the amount of light that comes through the lens.

What's commonly called aperture in photography is more precisely relative aperture, which in photography (although not always elsewhere) is the focal length divided by the pupil diameter.

For this reason, aperture (relative aperture) is properly expressed as either a ratio (e.g. "1:2.8") or, and much more commonly, as a number following "f/" (e.g. "f/2.8"). But the slash is commonly omitted ("f2.8"). Anyway, the smaller the number, the greater the aperture. Everyday lenses on SLR cameras typically have an aperture from f2.8 (or larger) to f16 (or smaller). A lens is commonly labeled with its maximum aperture.

With a "manual" or "semi-automatic" camera (i.e. a camera with manual or semi-automatic exposure control), for any light level you have a choice of different combinations of aperture and shutter speed. Call it progress or call it dumbing down: you now no longer have this choice unless you're willing to pay extra for it -- or of course unless you buy a good used non-digital camera.

The greater the aperture, the less the depth of field.

Kodak says that the aperture of the DC210's lens varies between f4 and f16.

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Focal length

In practice, focal length is a measure of the "telephoto-ness" of a lens. A zoom lens is one whose focal length you can vary. For a particular size of negative, slide, or CCD, the greater the focal length, the more the lens resembles a telescope. Because full-frame 35mm still cameras are so familiar, the focal length of the lens of a digital camera is often quoted in terms of its 35mm equivalent. Thus the Kodak DC210 has a "29-58mm" lens (though in reality of the order of one eighth of this).

Tastes and marketing policies change, but for a full-frame 35mm still camera, a 28mm lens is perhaps the commonest wide-angle, 50mm is "normal" (although longer than the fixed lens on typical point-and-shoot cameras), and 105mm is the typical choice of those who photograph people's heads.

The greater the focal length, the less the depth of field.

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Resolution in optics and (traditionally) in photography is not a matter of the size of the image but a measure of its quality or informativeness. Here's one explanation:

One way of testing lens performance is to observe the image it forms of patterns of increasingly closely spaced black lines separated by white spaces of line width. The closest spacing still recognizable in the image gives a resolving power value, expressed in line pairs (i.e., black line plus white space) per millimetre. Photographs of such line patterns, or test targets, show the resolving power of the lens and film combination. For example, a resolution of 80-100 line pairs per millimetre on a fine-grain film represents very good performance for a normal miniature camera lens.

Encyclopædia Britannica CD 97,
s.v. "Photography: Optical Performance".

Or more concisely:

The ability to separate visually or photographically adjacent small details.

D. A. Springer, The Focal Dictionary of Photographic
(London: Focal Press, 1973).

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Depth of field

Depth of field is

The region in front of and behind the focused distance within which object points still produce an image of acceptable sharpness. The extent of the depth of field depends on the aperture and focal length of the lens and on the distance on which it is focused as well as on the (arbitrary) standard assumed for 'acceptable' sharpness, and sometimes on factors connected with the lens design. Can be calculated theoretically from the above parameters.

D. A. Springer, The Focal Dictionary of Photographic
(London: Focal Press, 1973).

That the extent of the depth of field may depend on "factors connected with the lens design" might suggest that Kodak could have developed some innovative lens with a much greater depth of field than is normal. This is unlikely. First, such "deep-field" lenses would have been in the news. Secondly, the only ways of designing for an increased depth of field that are mentioned in the books I've seen -- Arthur Cox, Photographic Optics, 15th ed (London: Focal Press, 1974); Rudolf Kingslake, A History of the Photographic Lens (San Diego: Academic Press, 1989) -- involve a great increase in at least one other kind of aberration (see in particular Kingslake, pp. 187-8).

If the explanation in the Focal Dictionary is a bit austere, try the following.

When a camera is focused upon a particular object, other objects in the image area that are nearer or farther away from the camera may not be as sharply defined.
   This change in sharpness is gradual rather than abrupt; there is a zone in front of and behind the exact point of focus where the actual difference in sharpness is too small for the human eye to see. The extent of this zone of sharp focus is called the depth of field. It depends on the lens aperture, the focal length of the lens, and the distance between camera and subject. At a given distance from camera to subject, the smaller the aperture and the smaller the focal length, the greater will be the depth of field. For example, with a 135mm lens set at f/11 and focused on a subject 30 feet (10 meters) away, the depth of field is approximately 26.5 to 34.7 feet (7.9 to 10.4 meters). With a 50mm lens at the same focus and aperture setting, the depth of field is 15 feet (4.5 meters) to infinity. At larger apertures the depth of field for both the 135mm and the 50mm lenses would be shallower, but it would still be relatively [sic] larger for the 50mm lens than for the 135mm lens. In addition, for a given aperture for a given lens, the depth of field narrows as the point of focus moves nearer to the lens.

Myron Matzkin, "Camera: 1. Still Cameras,"
Encyclopedia Americana, 1997 ed.
(Incidentally, there's something distinctly
dodgy about the figures for meters.)

More often than not, large depth of field is useful, but a shallow depth of field can be very effective for rendering fuzzy what would otherwise be distracting, and photographers use fast shutter speeds and strong "neutral density" filters to reduce light for this purpose.

Great depth of field is necessary for a fixed-focus camera if that camera is to be at all versatile. You can design it for photographing what's more or less within an arm's reach, or you can design it for landscapes; if it doesn't have an extreme wide-angle lens, it won't be able to handle both.

(For excruciating detail, see Nick Sushkin's Depth of Field On-Line Plotter.)

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"Focus free"

Focus free is not a term that many dictionaries explain. Although it does appear in the online Hyperglossary of photography -- [now defunct?] -- it is not in any of the following -- all of which do explain fixed-focus:

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Cheap focusable cameras

Some autofocus digital cameras cost less in early September 1998 in Tokyo than did the Kodak DC210. Among them are the Ricoh DC-3Z (which also allows manual focus), the Sanyo DSCX-1, and the Fuji DS-30.

Outside Japan, the names, precise specifications, and price relationships may differ. Also, I have not used any of these cameras and therefore do not vouch for quality or good design.

(I'm not very keen on any digital camera I've seen. They'll probably improve with time. And if "electronic film cartridges" aren't mere vaporware, digital cameras may become unnecessary.)

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This page previously had a link to the Australian site "Designcafé" (aka "Publishing Essentials magazine"). In view of credible allegations of that site's serious copyright violation, I've removed the link. If you want to see the original article (and if it's still there), you'll be able to find it -- though I don't think you'll find it worth the effort.

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