Pentax K-x

Noise Reduction (5.95)

We used the default configuration for high ISO noise reduction in our testing, but the K-x offers some flexibility here. By default, high ISO noise reduction kicks in after ISO 800. However, through a custom menu setting, you can choose the setting to start applying noise reduction.

The noise reduction processing does have a significant impact, cutting visible noise by nearly half at ISO 1600.

We break down overall image noise into its component parts, red, blue, green, yellow and chroma (gray). If noise in one color channel is considerably higher than the others it can make noise visibility worse, but that’s not the case here. More on how we test noise.

Shooting in a well-lit environment, images from the K-x had higher noise levels than most of our comparison cameras, starting at nearly 1% at a low ISO 200 setting and becoming pretty much unusable at the top ISO 6400 level. We test image noise by shooting the X-Rite ColorChecker chart under bright 3000 lux studio illumination, using each high ISO noise reduction setting available, then run the test images through Imatest for analysis.

With the camera’s noise reduction processing turned off, the Panasonic GF1, with its small Micro Four Thirds format sensor, is the noisiest camera in our roundup by far, but the K-x performance is nothing to brag about either.

Crank the noise reduction setting to 11 and images at ISO 1600 become useable, though we’d stick with small reproduction sizes for anything beyond that. It’s interesting that, while photos taken with the Panasonic GF1 look awful at ISO 1600 or 3200 with noise reduction turned off, the highest of four available noise reduction settings dramatically reduces visible speckling and imperfections at these levels, and didn’t annihilate fine details in the image.

The K-x didn’t match the image noise performance of the other SLRs in our lineup, surpassing only the small-sensor Micro Four Thirds Panasonich GF1 in this test.

ISO Options

Available standard ISOs range from 200-6400, with an expanded ISO range from 100-12800. There’s an Auto ISO mode, which allows the user to limit the highest acceptable setting anywhere from ISO 200-12800.

ISO Comparisons
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO Low
ISO 200	ISO 100	ISO 100	ISO 200	ISO 100
ISO 200	ISO 100	ISO 100	ISO 200	ISO 100
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 200
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 400
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 800
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 1600
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 3200
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 6400
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1
ISO 12800
Pentax K-x	Pentax K2000	Canon EOS Rebel T1i	Nikon D5000	Panasonic Lumix DMC-GF1

NOTE: The images above are not used in our testing or scoring, but are included here to show real-world examples of the differences between cameras at the various ISO settings.