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Kodak announces high-ISO DCS 620x  
Monday, May 15, 2000 | by
In a nod to night sports shooters and other photographers who routinely shoot in available darkness, Kodak has announced the DCS 620x, a variant of the DCS 620 that features a working ISO range of 400 - 6400.

The 620x, which does not replace the 620 in Kodak's pro digital product lineup, features a new CCD (with the same 1728 x 1152 pixel effective resolution of the stock 620's CCD), lower-noise electronics and, most significantly, a colour filter array striped atop the CCD that uses cyan, magenta and yellow-coloured filters, instead of the 620's red, green and blue (below).

The decreased light absorption of the CMY filter array has the effect of boosting the CCD's sensitivity, paving the way for the extended ISO range of the 620x. The camera's optimum ISO range is ISO 400-4000, though sensitivity is settable up to ISO 6400. The 620x's feature set is otherwise identical to that of the 620.

Does it deliver better performance? Does the camera deliver the better high-ISO performance that its ISO range suggests? Yes, definitely. Both the stock DCS 620 and the Nikon D1 can be set to shoot at up to ISO 6400 as well (the 620 achieves this by underexposing two stops at ISO 1600, then applying exposure compensation in Kodak's acquire software). Above about ISO 800 on both cameras, however, noise begins to intrude in some lighting situations, which effectively limits both cameras to a practical top ISO of 1600, and sometimes less.

The noise in the 620 takes two forms: blue channel chrominance noise and high-frequency noise. The blue channel noise is easily dealt with by either Kodak's noise reduction feature or by Quantum Mechanic. High-frequency noise, often referred to by me as luminance pitting, is more difficult to filter, and can overwhelm a DCS 620 photo when it's sharpened for newsprint output, since the unsharp mask filter sees this noise pattern as an area of contrast be enhanced. A Nikon D1 high-ISO photo displays little chrominance noise, but is even more affected by high-frequency noise than the 620. All in all, the DCS 620 and Nikon D1 will deliver good results up to ISO 800 in practically any shooting situation, and acceptable results at ISO 1600 as long as the scene is evenly lit.

Perhaps the biggest improvement in 620x photos, then, is the reduction in high-frequency noise, relative to the 620 and the D1. In both bright and dark-toned scenes up to ISO 3200, expect to see little or no luminance pitting rearing its ugly head as a photo is sharpened for printing. Above that, however, some pitting is usually apparent; by ISO 6400, especially in dark scenes, the pitting reaches full volume.

Also much improved is saturation at ISO 1600 and above. While D1 colour saturation stays strong up to ISO 1600 and beyond, the 620's saturation falls off noticeably at the camera's upper ISO limit, rendering sports jerseys and other dominant scene colours fairly flat. Not so with the 620x. Colours remain vivid up to ISO 4000 in practically any shooting situation. In fact, sometimes colours are too vivid, especially at ISO 400 and ISO 800 in contrasty light. Fortunately, the upcoming v5.9.1 acquire software will include a reduced saturation option designed specifically to reign in lower-ISO 620x colour (below).

With this option enabled, 620x photos appear to have about the same colour saturation as stock 620 photos. In fact, 620x photos shot at lower ISOs look remarkably similar to those shot with a 620.

There is also an improvement in blue channel chrominance noise, though the degree of improvement changes drastically with the colour of light. In daylight-balanced light, expect to be impressed. Blue channel noise in an ISO 3200 620x photo is akin to what you might find at about ISO 1250-1600 in a 620 photo. The noise distribution is also more equitable. That is, chrominance noise is distributed more evenly through the red, green and blue channels in 620x frames, whereas in the 620 it's found almost exclusively in the blue channel. Kodak's own noise reduction feature dents this noise nicely; Quantum Mechanic, as usual, does a stunning job of cleaning up most of the chrominance noise in 620x photos at practically any ISO. The only situation in which the chrominance noise is difficult to tame is when the scene lighting is warm. Under tungsten or incandescent lighting the blue channel becomes choked with noise pixels, and 620x photos begin to look awfully similar to stock 620 photos at higher ISOs. Be aware of this when shooting under TV tungsten lighting, for example.

Conclusion If you regularly find yourself making pictures in little or no light, the DCS 620x will make it easier to obtain a printable image. The camera will be released June 1 at a list price of US$10,495. Effective today, the list price of the DCS 620 is reduced to US$8,995. Note that Kodak does not plan to release a high-ISO "x" version of the DCS 520 at this time, though as Kodak's 620x FAQ states, this "determination could change."

DCS 620x notes:

  • Areas in a photo that are completely blown out blink in black on the rear Image LCD Display, as they do on the display of a stock DCS 620. When areas are not completely blown out, but have a detail loss in only 1 or 2 channels, interpreting which channels are affected can be a bit of an adventure. With even slim knowledge of colour theory it's easy with the 620; for example, if an area of the image is blinking yellow, that means the opposite colour channel, the blue channel, has lost detail around that spot. The 620x's CMY-centric way of doing things, however, seems to make lost detail sleuthing more difficult. For example, when an area of yellow is not blown out in all 3 channels, it seems to blink light green; when an area of blue is similarly blown out, it also blinks light green. I suspect that I'm running up against the LCD display's ability to render certain colours accurately, thereby making it tricky to guesstimate what the opposite colour of the blinking colour actually is.

  • Nikon's SB-28D and SB-28DX speedlights include a modified automatic flash output mode, called Auto Aperture mode, designed specifically for the DCS 620. Auto Aperture mode is also available when either of these strobes is slid onto a 620x, but for some reason flash exposures are consistently 1 stop out. That is, a scene requiring no flash exposure compensation on the 620 will require -1.0 flash exposure compensation on the 620x. The flash behaves almost as if the base ISO of the camera is the 620's ISO 200, not the 620x's ISO 400, though the flash's LCD panel correctly displays the ISO set on the camera.

  • The 620x's firmware includes a couple of new items that will almost certainly appear in DCS 520/D2000 and DCS 620 firmware updates soon. They include an "Enable Sharpening" property, which, when used in conjunction with a setting in the preferences of the upcoming v5.9.1 acquire software, will switch on sharpening during the acquiring of DCS 520/D2000/620/620x photos. Related to this change is a fix for a long-standing acquire software quirk in which the image information would state that the anti-aliasing filter was removed from a camera that most definitely had the filter in place. Now, the image information indicates the user-selected sharpening preference instead.

For more information on the 620x, see Kodak's technical document and FAQ.

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