In trying to get a glimpse of how the Pentax KP might compete with the D500, I looked at test scene samples on DPReview. Keep in mind that the D500 retails at about three times the cost of the K-70, or a difference of 1300 to 1350 Eurodollars. That is, choosing the K-70, for the same budget, you could get at least four nice lenses, two great lenses, or one truly stellar lens in addition to the camera – or three bodies instead of one. Or two bodies and two nice lenses.
So is that price difference reflected in the raw output? Are images from the D500 three times as good? Let’s take a look:
The K-70 has slightly higher resolution – 24 megapixels rather than 20. Differences in pixel dimensions are difficult to compensate for in image quality comparisons. However, I think we can see that at sensitivities of ISO 51200 and 102400, chroma noise is very similar. It seems finer grained and less luminous in the Pentax, but the D500 looks like it has had more sharpening and contrast applied to it – hard to say if this was in-camera and, if not, owed to the default settings of Adobe Camera Raw, which DPR use to generate the above “raw” views.
Time and again, I found the image quality to be very similar, and I could not decide which camera I would prefer on that basis. Having said that, a camera is more than its image quality, and the D500’s buffer depth, to name just one aspect, far exceeds that of the K-70, but this is useful in a narrow range of shooting situations, primarily in wildlife and sports. Both cameras may be outdated in two years, and there’s no obvious reason to expect the depreciation on the D500 to be less than three times that experienced in choosing the K-70. So to continue our budget thinking, you could pick up a K-70 and two nice lenses now, and save the rest for an upgrade to the next mid-level camera from Pentax in 2019, all for the price of one D500 and a kit lens. If you’re anything but a pro who absolutely needs the capabilities of the D500 for sports or wildlife, or a wealthy amateur, that reasoning is hard to argue with.
By the way, if you’re worried about the disk space raw images will take, the 24 megapixel image from the K-70 was the same size at ISO 104200 as the D500 (20 megapixels), and slightly smaller at ISO 51,200, in spite of having the same bit depth (14 bits). At lower ISOs, the K-70 files are consistently about 20-25% smaller. So if you prefer resolution over other considerations, the K-70 has a slight edge without obvious disadvantages.
For an additional test, I passed both images through DxO’s PRIME noise reduction engine (click through for 1:1 view):
As before, the Nikon image has more contrast and looks more graded; in terms of noise and detail, after DxO PRIME treatment, both images have edge artefacts at this ISO. It is no surprise that the Pentax retains more detail in black and white areas. In textured areas, the winner is less obvious, and the Pentax image has grainier noise and shows the DxO artefacts more strongly.
Finally, comparing a pixel shift Pentax image with a normal Nikon capture, controlled for total exposure, shows no clear advantage, either:
The pixel shift image shows more detail as expected, but having, in the interest of a fair comparison, controlled for total exposure and thus compared Pentax at ISO 102400 to Nikon at 25600, the Nikon shows less noise.
In conclusion, at a technical level we can say that the Nikon D500’s slightly greater resistance to noise justifies its slightly lower resolving power, at 20 megapixels rather than the now ubiquitous 24 megapixels. However, justifying the price differential is an entirely different exercise, and the Pentax K-70 looks an extremely strong challenger. The Pentax KP is expected to build on the low light capabilities of the K-70 and exceed it, and at little over half the price of the Nikon, adds another strong option for the budget-conscious.
Strikingly, having compared the K-70 to Nikon’s other recent APS-C releases, it is obvious that the D500 is currently the only Nikon APS-C camera that’s still competitive with Pentax on image quality, other Nikons having been left in the dust.
And the successor of the Pentax K-3 II is only months away, with an announcement date around September, and will challenge the D500 on a broader set of features, including buffer depth.
Update: I added a comparison of the Pentax KP and K-70 at high ISO.