April 14 2011
The new Pentax K-5 Digital SLR is proving to be an outstanding digital camera for low light sports photography.
Pentax made major steps with their new K-5 in addressing tow key deficiencies in their recent DLSRs, autofocus performance and ISO range with low image noise. A session at local Roller Derby bout provided a good trial session for the K-5’s indoor sports capabilities.
Lab tests from DxOMark promised improved noise performance at high ISO settings compared to my old K10D, so the session was shot using TAv mode. This is Shutter speed and Aperture Priority combined, where the camera automatically selecting the ISO setting from the meter reading.
The Shutter Speed was selected for freezing the motion at a reasonably high 1/500 sec, while the aperture of the DA*50-135mm zoom lens was chosen at f3.5. A compromise between depth of field and letting in enough light to keep the ISO down. It is always good policy to use the lowest ISO practicable to minimise digital noise in the image. As always it is a compromise, the ISO has to be high enough for good exposure.
The resulting ISO setting was 2500, with exposure compensation set to underexpose by a third of a stop. This is in case the white tops of the Van Diemen Rollers ended up overexposed, as they are the most light reflecting objects in the setting. While this is well below the maximum ISO for the K-5 there is some obvious noise in the RAW images. However, the Noise Ninja plugin, the full registered version, in Bibble 5 easily made the images presentable without the plastic smeary look that results from large amounts of noise reduction processing.
The Pentax DA*50-135mm zoom is a premium lens with the expected f2.8 maximum of top lenses. The wide aperture lets in more light as the camera focuses and then the aperture closes to the smaller selected aperture when the shutter is released. As expected in premium lens of this type the lens incorporates a fast supersonic motor for Autofocus operation.
Sports photographers often use Continuous Autofocus mode, this is where the camera keeps focusing while the shutter is half pressed, or the AF button on the back of the camera is pressed. This technique does take some practice, particularly after years of manual focusing for sports.
As a late adopter of Autofocus technology, it was not until my first Digital SLR replaced the venerable Pentax Kx, an all manual film SLR in 2004, with a new *istDS. Too many out of focus motor sport pictures prompted a return to long established manual focus techniques for action shots. The updated SAFOX +IX Autofocus system in the Pentax K-5 coupled with a Supersonic Drive Motor (SDM) lens is proving far more capable of tracking moving subjects than the older Pentax K10D.
With the focus point selection mode set to auto the Pentax K-5 consistently focussed on the roller derby girls near the centre of the frame, rather than others on the periphery of the action.
The practical photo shoots confirm the DxOMark lab tests that the Pentax K-5 reliably produces useable digital images under low light conditions with little noise distortion. The field experiences also confirm the effectiveness of the upgraded autofocus system for tracking moving subjects in sports events.