What is the crop factor of the Pentax 645Z?

The Pentax 645Z is equipped with a medium format sensor, whose diagonal measures 54.7mm. The sensor has a crop factor (or format factor, or focal length multiplier) of 0.79.

The crop factor is defined as the ratio of the 35mm full-frame film diagonal to the diagonal of a digital sensor. This number indicates how a lens behaves in relation to the size of the image sensor.

Sensor size comparison with a film slide

With a crop factor of 0.79, the sensor in the Pentax 645Z is larger than the receptor area of a 35mm film slide or negative. As a result, a lens that is attached to the Pentax 645Z will offer a wider angle of view and provide shallower depth of field than a lens of similar focal length and aperture on a film camera. The equivalent focal length is obtained by multiplying the actual focal length of the lens with the crop factor. For example, a 63mm lens on the Pentax 645Z will provide the same angle of view and depth of field as a 50mm normal lens on a film camera (63mm * 0.79 = 50mm).

Sensor specs and performance

The table below compares the sensor specs of the Pentax 645Z to those of several similar cameras. The reported DXO values are indicators of the sensor's imaging quality (higher is better), covering color depth (DXO Portrait), dynamic range (DXO Landscape), and high-ISO noise (DXO Sports). Larger sensor cameras tend to outperform cameras of the same generation that are equipped with a smaller imager. On the other hand, larger sensors are more expensive and require bigger and heavier lenses than smaller light receptors.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
2.		Canon 1D X Mark II	Full Frame	20.0	5472	3648	4K/60p	24.1	13.5	3207	88
3.		Canon 5DS	Full Frame	50.3	8688	5792	1080/30p	24.7	12.4	2381	87
4.		Canon 5DS R	Full Frame	50.3	8688	5792	1080/30p	24.6	12.4	2308	86
5.		Hasselblad X1D	Medium Format	51.3	8272	6200	1080/25p	26.2	14.8	4489	102
6.		Leica M11	Full Frame	60.3	9528	6328	none	26.3	14.8	3376	100
7.		Leica SL	Full Frame	24.0	6000	4000	4K/30p	25.0	13.4	1821	88
8.		Nikon D4S	Full Frame	16.2	4928	3280	1080/60p	24.4	13.3	3074	89
9.		Nikon D5	Full Frame	20.7	5588	3712	4K/30p	25.1	12.3	2343	88
10.		Nikon D7200	APS-C	24.0	6000	4000	1080/60p	24.5	14.6	1333	87
11.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82

In the United States, the 645Z was initially launched in April 2014 at a price of $8,499.

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Camera to camera comparisons

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