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Posted by | Jan 22, 2017 | , , ,



Fujifilm GFX Crop Factor and GF Lens 35mm Full Frame Equivalent Focal Lengths



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The new mirrorless medium format Fujifilm GFX system has really shaken the camera industry lately, and judging by the initial responses from photographers I know, this is a format and camera system that’s going to be around for some time. There’s never been a more affordable way to get into digital medium format photography before, and whilst Pentax paved the way over recent years with the Pentax645Z, the new Fujifilm GFX system undercuts its price significantly, whilst also delivering a set of specifications that makes the Pentax camera look quite ancient.  I believe Fujifilm has a real winner on their hands here, so I’ve decided to add some content and resources to the site relating to this interesting system.

CALCULATING 35MM EQUIVALENT FOCAL LENGTHS FOR FUJIFILM GF LENSES



Since most people are used to seeing focal lengths in 35mm terms, it’s a bit confusing for many of us to see the focal lengths of the new Fuji GF lenses, and immediately comprehend how wide, or telephoto the lenses are. To be able to compare the field of views from full frame and GF lenses, we need to know what the crop factor is for the GFX system.

 

CROP FACTOR FOR FUJIFILM GFX SYSTEM CAMERAS

Crop factor is the ratio of the diagonal dimension of two camera’s sensors. If you know the width and height of a sensor, you can calculate the diagonal dimension using Pythagorean theory. Then you simply divide the diagonal dimension of a full frame sensor, by the diagonal dimension of the sensor for which you want to find the crop factor, GFX system in our case. Most of us are used to seeing crop factor as a number greater than 1, for example APS-C is typically has a crop factor of 1.5x or 1.6x. Since the GFX system has a sensor that is larger than full frame, we can expect our crop factor to be less than 1. In other words, 35mm full frame equivalent fields of view will be larger than the quoted focal length for any given GF lens.

THE MATH WORKS OUT AS FOLLOWS:

Full frame sensor dimensions: 36mm x 24mm therefore diagonal dimension is  √(362 + 242) = 43.27mm

GFX format sensor size: 43.8mm x 32.9mm therefore diagonal dimension is  √(43.82 + 32.92) = 54.78mm

Crop factor for Fujifilm GFX system = 43.27/54.78 = 0.79





FUJI GF LENS EQUIVALENT FIELD OF VIEW TABLE






Using the calculated crop factor of 0.79, we can now see the 35mm equivalent field of views for all the Fuji GF lenses.

Lens 35mm Full Frame Equivalent Equivalent F-Stop
GF 23mm f/4.0 18mm f/3.2
GF 32-64mm f/4.0 25-51mm f/3.2
GF 45mm f/2.8 36mm f/2.2
GF 63mm f/2.8 50mm f/2.2
GF 110mm f/2.0 87mm f/1.6
GF 120mm f/4.0 OIS Macro 95mm f/3.2