Pentax K-3 Comparative Crops

Current DSLRs are available in two sensor-sizes: APS-C or Full-Frame. The former has a smaller sensor which is 1.5X smaller diagonally compared to the latter which has the same sensor-size as 35mm film. Pentax makes APS-C DSLRs only, while Nikon and Canon make DSLRs with either size of sensor. Technically, Canon APS-C cameras have slightly smaller sensors, 1.6X smaller compared to full-frame.

Full-frame DSLRs are theoretically advantegeous since their larger sensors let them collect more light per area. Practically speaking, technology and sensor-design plays a huge role in sensor-performance. We compare the K-3 versus the Nikon D610
Nikon D610 to evaluate the real-life performance difference among state-of-the-art DSLRs.

Pentax K-3	Nikon D610
	ISO 50
ISO 100	ISO 100
ISO 200	ISO 200
ISO 400	ISO 400
ISO 800	ISO 800
ISO 1600	ISO 1600
ISO 3200	ISO 3200
ISO 6400	ISO 6400
ISO 12800	ISO 12800
ISO 25600	ISO 25600
ISO 51200

The above 100% crops show that image-noise is nearly identical at low sensitivities. By ISO 1600 though, the full-frame advantage becomes clear. The difference widens towards the end of the range but never exceeds a full stop. This is an excellent performance for the K-3 which shows that it is equally usable for low-ISO but full-frame cameras are better for low-light hand-held photography.

Note that sharpness appears quite different. There are two reasons for that. The main is optics. The lens in use on the K-3 is an ultra-sharp prime while the D610 used a variable aperture zoom. This underlies the importance of quality lenses. The second reason is a different JPEG rendering engine. Pentax uses superior sharpening to produce crisper edges before introducing artifacts.