Lab Test: Pentax K-5

With New York City pummeled by multiple snowstorms this winter, our staff was happy to have the Pentax K-5 around. Fully weathersealed and built to function in temperatures as low as 14 degrees Fahrenheit, Pentax’s new flagship DSLR ($1,470, body only; $1,580, with 18–55mm f/3.5–5.6 WR lens) didn’t even flinch as foot after foot of snow covered our metropolis. And given the image quality that the K-5 delivers, we were just as pleased when reviewing our images after we came in from the cold.

In the Lab
Helped by a new 16.3MP CMOS sensor that captures RAW images with 14 bits per color channel, the K-5 earned an Excellent rating in the Popular Photography Test Lab from its lowest sensitivity of ISO 80 through ISO 400—the first Pentax DSLR to do so under our latest, and most stringent, test criteria. In our resolution test, the camera served up 2590 lines per picture height for an Excellent rating, a solid showing for a 16MP sensor.

Color accuracy also got an Excellent rating, with an average Delta E of 7.1. This marks an improvement over this camera’s predecessor, the K-7, which didn’t make it past the Extremely High mark in this test. In this test, the K-5 essentially matches the Olympus E-5, its only real competitor in this class of camera, which is to say more expensive than the Canon EOS 60D or Nikon D7000, but less expensive than the Canon 7D or Nikon D300s.

Noise can be a controversial topic when it comes to Pentax’s high-end cameras. The company chooses to tread extremely lightly with noise reduction, which means that its cameras end up with higher noise numbers than they would if the engineers were a bit more aggressive in this area. Pentax does apply an increasing amount of color noise reduction as ISO increases, but not luminance noise reduction.

That said, the K-5 keeps noise to a Low or better rating up to ISO 400. It remains in acceptable territory up to ISO 1600 and just barely edges into an Unacceptable rating at ISO 3200. Even a judicious use of noise reduction will bring that into our acceptable range without a serious effect on resolution, which remains at an Excellent rating up to ISO 12,800 using Pentax’s default noise-reduction settings. And if you’re willing to sacrifice an appreciable amount of resolving power, you can likely bring noise into acceptable territory at ISO 6400.

Considering that the Olympus E-5 resolved only 2270 lines at its best, when you balance resolution and noise reduction, the K-5 earns a slight edge over its main competitor—as long as you’re willing to experiment a little and find the amount of noise reduction that’s right for you. Also, while sensitivity on the Olympus tops out at ISO 6400, the Pentax keeps going up to ISO 51,200, with 1/3-EV increments all the way to the top.

Fast in bright light, though sluggish in low light, the K-5 showed a slight improvement over the K-7 in our autofocus speed test, but this remains one of the drawbacks of Pentax’s top DSLR. Of course, the same can be said for Olympus, though the E-5 fared slightly better at moderate light levels, while the Pentax beats it in the dimmest light.

Both cameras are extremely fast in bright light. In fact, in the brightest level of our test, the K-5 focused in 0.28 sec, exactly matching the E-5’s result. Both cameras stepped down to 0.48 sec in nearly identical increments by EV 6, which is about the light level of a well-lit kitchen. At this point the K-5 takes a big drop to 0.80 sec at EV 4, while the E-5 focused in 0.56 second. By EV 1, both cameras focus in just under a second, while at the moonlit dark of EV 0, the Pentax focused in 1.17 sec, while the Olympus dropped to 1.32 sec. One thing the Olympus has in its favor: It was able to focus reliably, albeit very slowly, at our test’s lowest light level of EV –2, while the Pentax couldn’tfocus in such dim light (Pentax rates the K-5’s AF as functional only down to EV –1).