The Pentax K-7 gets a photo-facts tech award because it has three very useful features which set it apart from other digital SLRs. Pentax is to be commended for tackling issues which really do make a big difference to image quality rather than simply cramming in gadgets or trying to come up with ever bigger numbers to beat its rivals with.

These three features are not headline grabbing specifications, though, so they’re easily overlooked. They are:

• Expanded dynamic range • Distortion correction • Chromatic aberration correction

1. Expanded dynamic range

Dynamic range is a problem for all sensors, specifically the way bright highlight detail is often lost, or ‘blown’. Pentax has tackled this in previous D-SLRs with an expanded mode dynamic mode range which selectively adjusts the ISO in different parts of the scene according to the brightness. Pentax has claimed this offers a 200% increase in dynamic range and the results bear this out. Previous models have been able to shoot JPEG images with the kind of dynamic range and highlight retention that other cameras can’t (unless you shoot RAW and use a RAW converter which offers highlight recovery).

In the K-7, this feature has been enhanced to offer separate controls for shadow and highlight detail. You can enable extra dynamic range in either or both. For most photographers it’s the highlights which are the problem, and being able to enhance these alone may prove useful.

2. Distortion correction

Distortion is a big problem for anyone who uses a zoom lens. Typically, zooms exhibit barrel distortion at their shortest focal lengths and pincushion distortion at the longest. This diagram from the K-7 manual illustrates the effect.

With some cameras you can shoot RAW files and then use the camera maker’s own RAW conversion software to correct the distortion, using EXIF information embedded in the image file to identify the lens and focal length (or use DxO Optics Pro, which comes with camera/lens specific profiles). The only other alternative is correct distortion manually, by eye, using tools like Photoshop’s Lens Correction Filter. This is slower and less satisfactory.

The K-7, though, has distortion correction built in. The body can correct any lens distortion even as the image is being saved to the memory card. Again, Pentax has incorporated a feature which enables photographers to shoot JPEGs whereas before they might have had to shoot RAW and go through a separate correction process. Pentax says this feature will work on all Pentax DA, DA L or D FA lenses.

3. Chromatic aberration correction

The chromatic aberration correction works on the same basis, automatically correcting aberration (colour fringing) for compatible lenses. It shares the same menu screen as the distortion correction function above. Chromatic aberration is a problem on all zooms, regardless of price, and some other makers (Nikon, Panasonic) use a similar approach in some of their models, applying in-camera correction as the image is processed.

Again, this is a very valuable function. Usually, your only chance of automatic correction is to shoot RAW and hope that the camera maker’s RAW conversion software has the necessary option. The other alternative is to correct colour fringing manually, again with a tool like Photoshop’s Lens Correction filter. This does work, but it’s slow, it can be difficult to get right and every shot will need individual attention.