The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). We found that measured ISO from the K-30 is roughly 1/3EV lower than indicated - so ISO 100 = ISO 80 (approx). This holds true throughout the entire ISO range, but a discrepancy this small has little practical impact upon everyday photography (remember that this test is performed in manual mode without reference to the camera's metering system).
Noise and Noise Reduction (JPEG)
This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F).
Note: this page features our new interactive noise comparison widget. By default, we show you the default noise reduction settings of the camera a tested, and three other models of the same class. You can select from all available NR options, and from other cameras. The 'tricolor' patches beneath the familiar gray/black/portrait images are taken from the same test chart, and show how noise impacts upon blue, green and red areas of a scene.
ISO range noise comparison
The Pentax K-30 performs very well in terms of image noise and is one of the very best APS-C cameras currently available in this respect. At default settings the Pentax keeps a good balance between noise reduction and retention of fine detail up to very high ISO levels. At ISO 1600, which only a few years ago would have meant noisy and blurry images, you can zoom into your images and not notice any noise or detail blurring. Even images that have been taken at ISO settings as high as 6400 noise are perfectly usable, even for letter-sized prints.
The Pentax K-30 offers four noise reduction settings - Off, Low, Medium, High, plus Auto and Custom modes. Auto is the default setting, which calculates and applies an 'optimized' amount of noise reduction at each ISO step. The Low, Medium and High settings apply a constant level of noise reduction across the ISO range, and in Custom mode the noise reduction setting can be defined by the user for each sensitivity setting (so you could choose 'Off' at low ISOs, 'Medium' for moderate ISOs and 'High' for ISO 12,800 and 25,600, for example).
Raw noise (ACR 7.2, noise reduction set to zero)
There are minor signs of noise even at the lowest sensitivity settings (remember these samples have noise reduction turned down to zero in ACR) but from the very lowest ISO settings it becomes evident that the Pentax output is cleaner than most cameras in its class. Some noise reduction is applied to Raw files at ISO 3200 and higher, regardless of how you have high ISO noise reduction set in the menu system, but the effect is subtle, and does not appear to have a significant impact on detail reproduction.