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White Balance

The DX7590 has just four white balance presets in addition to the auto default; daylight, tungsten, fluorescent and open shade. There is no manual (measured or custom) white balance function. It's a good job then, that the auto white balance performs so well, particularly in 'difficult' lighting (fluorescent and incandescent). There is a slight warm tone to both our artificial lighting samples, but it is much better than many competitors.

Outdoor - Auto WB
Red 0.9%, Blue 0.9%,
Excellent

Fluorescent - Auto WB
Red 1.6%, Blue -1.0%,
Good
Incandescent - Auto WB
Red 1.4%, Blue -2.7%,
Good

Flash Performance

Aside from some cut-off when the flash is blocked by the lens with very close subjects there's little to complain about here. Exposures are excellent and color almost perfect. Fill flash is well balanced and the slow-sync works very well.

Skin tone
Excellent color, Good exposure
Color chart
Excellent color, slight underexposure

Macro Focus

The DX7590's macro function gets you down to about 12cm (4.7 inches) at the wide end of the zoom, capturing an area around 6cm across, though there is obviously a price to pay in the form of distortion (common to most digital camera macro modes). At the telephoto end of the zoom the area captured is around four times bigger (just over 11cm across), and there is still some distortion, though less so.

Wide macro - 61 x 45 mm coverage
34 px/mm (851 px/in)
Distortion: High
Corner softness: Low
Equiv. focal length: 38 mm
Tele macro - 112 x 84 mm coverage
18 px/mm (461 px/in)
Distortion: Average
Corner softness:Average
Equiv. focal length: 380 mm

Barrel and Pincushion Distortion

No real problems here - 1.3% barrel distortion is well within the expected boundaries of a lens of this type, and there is no measurable distortion at all at the telephoto end of the zoom (except in macro mode - see above).

Barrel distortion - 1.3% at Wide angle
Equiv. focal length: 38 mm
Pincushion distortion - 0.0% at Telephoto
Equiv. focal length: 380 mm

Specific image quality issues

First the good stuff. Images from the DX7590 have typical Kodak color - rich, saturated and vibrant, yet very natural, meaning most of the target audience will be overjoyed at the bright punchy prints they get without any post-processing. Exposure is good - though far from foolproof - and I reckon I got a hit rate of about 90%, with the remainder marred mainly by focus errors or camera shake at the long end of the zoom or by underexposure problems caused by having too much sky in the scene. As seen in the studio shots there is some drop-off in sharpness at the corners of the frame, but this doesn't really show in everyday shots at 'normal' print sizes (under 10x8 inches) and is minimized by avoiding the widest aperture settings.

Look a little more closely at the images, however, and the critical eye starts to see some problems - mostly a lack of 'biting' tack-sharpness. Some of the fault for this must lie at the door of the lens itself (the relatively high default sharpening would seem to reflect a desire on Kodak's part to put back what the lens misses, resulting in visible halos on some shots). The noise reduction system - so effective in keeping the dreaded graininess at bay - also seems to have a part to play in the softness of the images. At higher ISOs (especially 400) the approach is so heavy-handed that the results look almost like watercolor paintings. Finally, I'd like to have seen a lower level of compression (or an uncompressed TIFF option) offered for really important shots.

In the final assessment though, it must be stressed that for most users the DX7590's results will be more than satisfactory, and the softness will have little impact on the standard postcard-sized prints most people will produce. If you're a detail freak, however, you may find the images lack the critical sharpness you demand.

Color fringing

Although it's worst in areas of high contrast and/or overexposure, and at the widest (F2.8) aperture, fringing is visible in the corners of the majority of wideangle shots. To be fair this is about as bad as it gets, and in most shots you have to look very closely at the prints to see the effect at all.

100% crop 38 mm equiv., F2.8

Burnt out highlights/Dynamic range

As is common with such small, high pixel count chips, the DX7590 struggles with scenes containing a wide dynamic range. This, combined with a tendency to exposure for the shadows in the scene means blue skies all too often turn white, especially the paler blue skies of the winter months. If you look at the reflection in the stream in the shot below you can clearly see the sky detail the camera failed to pick up.

100% crop 38 mm equiv., F2.8
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