Pentax KP Review

High ISO Low Light Performance

The Pentax KP's top ISO setting is 819,200, the highest of any Pentax DSLR to date. While we would not have high expectations to the image quality at ISO 819,200, we would expect that the KP can produce good results at a sensitivity setting one or two stops higher than, say, the K-3 which tops out at ISO 51,200.

The scene

To find out about this we shot the night scene shown above with both cameras running through the entire ISO range. We included the K-1 in the test, more about that later. All images on this page were shot on tripod with the HD Pentax-D FA 28-105mm zoom. In-camera lens corrections were set to off. Shadow and highlight correction were set to Auto. Slow shutter speed noise correction was off and high ISO noise reduction was set at the camera defaults. Pixel shift and the AA filter simulator were off.

First we compare the KP at ISO 25,600 (left below) with the K-3 at the same ISO (right below). The images are full resolution, but cropped JPEGs straight out of the cameras with custom image set to Bright with default settings of sharpness, contrast, and noise reduction. Both images were exposed at 1/10s F6.7:

The KP clearly creates the cleaner image with more detail and less noise. Observe in particular the noise on the right hand side of the car in the K-3 image.

Next we compare the KP at ISO 51,200 (left below) with the K-3 still at ISO 25,600 (right below):

The KP shows more detail and a smoother noise pattern than the K-3 even when the KP is set to an ISO value 1 EV higher than the K-3.

Finally let's compare the KP at an ISO setting two stops higher than the K-3:

Here the scale has tipped ever so slightly over to favor the K-3 which lets us conclude that at high ISO the KP allows for shooting with an ISO setting almost two times higher than the K-3 for similar image quality (detail, noise). The KP is an impressive improvement over the K-3.

In the following table we compare the KP and K-3 through the entire ISO range based on JPGs from the cameras. Click the thumbnails to enlarge and browse. The images are 100% crops 1400 pixels wide. Only if your monitor is wide enough will you see these crops in full resolution.

ISO	KP	K-3
100
200
400
800
1600
3200
6400
12 800
25 600
51 200
102 400
204 800
409 600
819 200

From ISO 100 to ISO 1600 the image quality is largely the same, but from ISO 6400 the KP pulls well ahead of the K-3. What is the highest useable ISO then with the KP? We cannot provide a general answer because it depends on the scene and also on the size at which you want to view (or print) the image. At the 100% crop level the upper limit is ISO 12800 or perhaps 25600, but when viewing the entire (uncropped) images of the above scene on our 27 inch monitor even ISO 102,400 is acceptable although shadow details are gone and the shadows get quite noisy. Overall, the KP's high ISO performance is impressive!

Crop of the image downsampled to fit our 1440 x 2560 px monitor

By shooting RAW and tweaking the raw image one can control the balance between less noise and higher resolution rather than accepting what the built-in JPG engine does. Looking at the images above it is perhaps not worth the extra effort to shoot in RAW except for especially valuable images.

High ISO Noise Compared to the K-1

Doing a fair comparison between formats is tricky. One school advocates downsampling the higher resolution images from the K-1 to the resolution of the KP, another school advocates the opposite: Upsampling the KP images to match the K-1 resolution. In our opinion the most relevant comparison depends on the intended use of the end product, in other words, both images should be resampled to match the print size desired or the size of the monitor used for viewing.

Since we don't have a specific end use in mind we present two sets of comparisons:

• KP at full resolution (4000 x 6016) compared to K-1 downsampled to 4000 x 6016
• KP upsampled to 4912 x 7360 compared to K-1 at full resolution (4912 x 7360)

The images are full resolution (100%) crops 1400 pixels wide. Only if your monitor is wide enough will you see the images in full resolution. Click a thumbnail to enlarge and browse the full resolution crops.

ISO	KP	K-1 (Downsampled)
100
12 800
25 600
51 200
102 400
204 800
409 600
819 200

The K-1 shows more detail, better dynamic range, and less noise from ISO 100 through ISO 51,200. At ISO 102,400 we deem the KP image the winner due to less noise even though it has less detail than the K-1 image. At ISO 204,800 the KP has pulled ahead of the K-1.

ISO	KP (Upsampled)	K-1
100
12 800
25 600
51 200
102 400
204 800
409 600
819 200

The ISO 100 image from the KP upsamples pretty well, although unsurprisingly the image from the K-1 is the better one. The K-1 is ahead up through ISO 51,200. At ISO 102,400 and 204,800 the upsampled KP images have a nicer noise pattern albeit at a loss of some of detail.

Verdict

The Pentax KP has the best high ISO performance we have seen so far from a Pentax APS-C DSLR. Compared to the K-3 which a has the same size sensor, the two are more or less equal up to and including ISO 3200, from then on the KP pulls ahead by about one and a half ISO steps. Even images shot at ISO 102,400 with the KP are useable when viewed on a 27 inch monitor.

Compared to the 35mm full frame format K-1, the KP is trailing in image quality through ISO 51,200, but pulls ahead thereafter with smother noise albeit at the cost of less detail.