We recently acquired a Pentax K-3 for review and decided to put the camera to the ultimate test–a 24 MP APS-C sensor camera versus a 24 MP full frame sensor camera. Although this sounds like a completely unfair test, the Pentax DSLR lineup has garnered quite a bit of admiration for its image making capabilities. In fact, others like phototheology on youtube showed the K-5 IIs dominating the Canon 5D Mark III, the Nikon D4 and the Nikon D7100. So why not put the Pentax K-3 up against one of the best selling full frame cameras currently available? We figured the Pentax would do a good job, but we never imagined the results would be so outstanding. Our testing shows that the Pentax K-3 swept the Nikon D600 in almost every image we took. Even at high ISOs the Pentax held its own against the full frame sensor!

In an attempt to show the image quality of the Pentax K-3’s 24 MP APS-C sensor compared to that of the Nikon D600‘s 24 MP full frame sensor we set up a head-to-head, real life competition between the two (pixel peepers will enjoy our upcoming static studio head-to-head that will be posted shortly). Here’s how we did it: on the Nikon D600 we attached a Nikkor 85mm f/1.8 lens and on the Pentax K-3 we attached a Pentax 55mm f/1.4 lens. These two lenses are both high quality, sharp lenses with very similar focal lengths (Nikon =85mm, Pentax=82.5mm when the crop factor of the APS-C is taken into account) and very similar maximum apertures. In our testing, we used various apertures, but did not use the maximum aperture for either lens to account for the variation between the two. For each image taken, we used the same aperture on both cameras. Also, the cameras were on the same ISO setting. We set each camera to the aperture priority mode and allowed the cameras to choose the most appropriate shutter speed for the situation. This set up gave us maximum control over the test while trying to remove the “user error” variable of setting a camera to full manual setting. The exposure was center weighted.

Each image was taken in a RAW format then converted to JPGs through Lightroom. No adjustments were made to the images before publishing this article.

In almost every shot, the Pentax K-3 had much better color quality than the Nikon D600. Also, the Pentax K-3 did a much better job of auto selecting the appropriate shutter speed while having the camera set to aperture priority. The Pentax K-3 also did a better job of rendering a more pleasing contrast in a variety of situations. Finally, the image sharpness was visibly more appealing in the Pentax K-3 than the Nikon D600.

This test clearly shows the full frame Nikon D600 does not have image quality that is nearly as appealing or accurate as the cropped sensor Pentax K-3. Plus, the Pentax K-3 is currently $500 less expensive than the Nikon D600.

But what about high ISOs? No worries high ISO shooters. We have another article that will be posted soon to highlight the camera’s ability to handle itself in extreme conditions. Until then, I added a few screen shots of side-by-side comparisons for the two cameras with three different ISOs.

Nikon D600 / ISO 200 / 1/1000 sec / f/4

Pentax K-3 / ISO 200 / 1/800 sec / f/4





Nikon D600 / ISO 400 / 1/60 sec / f/4

Pentax K-3 / ISO 400 / 1/60 sec / f/4





Nikon D600 / ISO 400 / 1/250 sec / f/4

Pentax K-3 / ISO 400 / 1/320 sec / f/4









Nikon D600 / ISO 800 / 1/200 sec / f/4

Pentax K-3 / ISO 800 / 1/200 sec / f/4

Nikon D600 / ISO 6400 / 1/500 sec / f/5.6

Pentax K-3 / ISO 6400 / 1/640 sec / f/5.6

Nikon D600 / ISO 6400 / 1/800 sec / f/5.6

Pentax K-3 / ISO 6400 / 1/800 sec / f/5.6

Nikon D600 / ISO 400 / 1/160 sec / f/2.8

Pentax K-3 / ISO 400 / 1/200 sec / f/2.8

Here are a few side-by-side examples of 100% crop. Nikon D600 is on the left. Pentax K-3 is on the right.

ISO 400

ISO 6400

ISO 12800

Update 10/27/13

For those of you concerned about the validity of the test due to the dog picture, rest assured knowing that I could never recreate that “almost identical” picture again if I tried. I am attaching the shot taken prior to the ones shown above with both cameras to show you that it was a total fluke. I wish I could tell you that I’m just that good, however, it truly was a just a fluke. As you can see from my other images, some are more similar than others.

Nikon D600 / ISO 200 / 1/40 sec / f/4

Pentax K-3 / ISO 400 / 1/60 sec / f/4

I didn’t choose this set of images for two reasons. First, Max, the boxer, turned his head just as I clicked the shutter on the Pentax K-3 image. This ended with an image that had some blur around his head due to the quick motion (1/60 sec shutter speed), resulting in an image that was not good for comparative purposes. Second, on the Nikon D600 shot, Ruby the Yorkie Poo, was turned and I also realized my ISO was set for 200 giving me a shutter speed of only 1/40 second. I quickly changed my ISO to 400 and then reshot the image. The reason the dogs looked so still in both of the images shown in the original part of this article was because they were watching the neighbor’s horse that was just on the other side of the fence. Here is an image of Shelby the horse being watched intently by Max (taken with the Samsung Galaxy NX camera on a different day). Sorry, guys. No conspiracy here. I’m just doing my best to show off the capabilities of each camera in a way that is as fair and unbiased as possible.

Tell Us What You Think

Which would you choose, the Nikon D600 or the Pentax K-3? For those looking for a depth of field comparison, weigh in on our forum and let me know exactly what you would like to see. Would you rather see real world comparisons or a static studio comparison (like the 12800 ISO shot shown above)? I generally tend to show real world comparisons because that’s how I use my camera, but I am happy to run the test however you like! Just let me know.