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Image Quality / DCS Photo Desk Features

Because the DCS 760 doesn't yet support in-camera JPEG and doesn't have any in-camera image processing algorithms (such as colour, tone, sharpening etc.) the actual final image quality comes down to how well DCS Photo Desk processes the RAW (.DCR) files. Kodak are promising in-camera JPEG creation sometime around September.

The two main areas of interest knowing the DCS 760's history will be noise in the blue channel and moiré artifacts (because of the lack of an anti-alias filter). DCS Photo Desk can compensate for both of these problems with its built-in noise / moiré reduction.

We'll be examining image quality in parallel with the features in Photo Desk which have a direct effect on them.


Colour space

Before we go much further I should talk about the Colour space available when using DCS Photo Desk, it allows you to save JPEG files in the Kodak DCS 'standard' colour space (as near to sRGB as you can get) and also in the new very wide gamut ProPhoto RGB. A CIE chromaticity chart showing ProPhoto RGB, Wide Gamut RGB, Adobe RGB, sRGB and CMYK can be seen below:

This from a Kodak document:

What is the ProPhoto RGB working space?

The ProPhoto RGB working space is an idealized color space defined in terms of gamma, white point, and phosphor settings. The compatibility of ProPhoto RGB parameters with Photoshop working space requirements lets you use the ProPhoto RGB working space as an intermediate and convenient color space in which to store, edit, archive, and transfer color data for imaging applications that use ICC-compliant profiles (for example, QuarkXPress 4, PageMaker 6.5, InDesign, OPI servers, and ICC compliant RIPs).

Obviously you can't just display a ProPhoto RGB in a web browser without it looking 'dull' (because currently there's no way to embed ICC profiles into web pages). The samples below are provided so you can examine the colour space yourself in an application which understands ICC profiles (such as Adobe Photoshop). You can download the Pro Photo RGB ICC profile here. All images were processed as TIFF and converted to JPEG later.

Kodak DCS 'Standard' colour space (close to sRGB) / 1,052 KB JPEG
ProPhoto RGB colour space, / 1,534 KB JPEG
Linear (no colour space, no gamma) / 1214 KB JPEG


ISO sensitivity (camera setting)

The sensitivity (ISO equiv.) at which the image is shot is clearly a camera setting and thus the results below represent the quality and noise levels from a RAW file converted without any noise reduction. The DCS 760 offers a range of ISO equiv. sensitivities: ISO 80, ISO 100, ISO 125, ISO 160, ISO 200, ISO 250, ISO 320, ISO 400. For brevity I've chosen to shoot the following samples at ISO 80, 100, 200 and 400. All images were processed as TIFF and converted to JPEG later.

Good light Low light
ISO 80, 1/4 sec, F9.0 ISO 80, 4 sec, F9.0
ISO 100, 1/5 sec, F9.0 ISO 100, 3.2 sec, F9.0
ISO 200, 1/10 sec, F9.0 ISO 200, 1.6 sec, F9.0
ISO 400, 1/20 sec, F9.0 ISO 400, 1/1.3 sec, F9.0

The ISO 400 top end is probably the camera's biggest single limitation, you can of course deliberately underexpose by one or two stops and 'push' the image (which will give you an effective ISO 800 or 1600) but there's good reason that Kodak limit the selection of sensitivity to ISO 400. Put simply our old friend (and Kodak's bane) blue channel noise starts to become a real problem around ISO 400. I must also admit I was quite surprised to see hot pixels starting at 1 - 3 second exposures on a Pro Digital.

The crops below are of the orange crayon from the good light samples above and show JUST the blue channel, as you can see there's even noise at ISO 80, that (logically) gets gradually worse as we turn up the sensitivity.

ISO 80, 1/4 sec, F9.0 ISO 100, 1/5 sec, F9.0
ISO 200, 1/10 sec, F9.0 ISO 400, 1/20 sec, F9.0

Thankfully Kodak have included a noise reduction option in DCS Photo Desk which can do a fairly good job at dealing with it (though obviously it would be more preferable not to have the noise in the first place).

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