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KB 2239

How does the image size of the sensor in digital backs effect image angle of view?

Last updated: 19-08-2015

Problem

The sensor in some Phase One backs is smaller than the medium format film that lens angle of views calculations have traditionally been based on. Also known as lens conversion or magnification factor.

Solution

To calculate the digital angle of view simply multiply the medium format film focal length by the Lens factor resulting in the approximate digital angle of view.  For example,  I am shooting on a 645 camera with the H20 and a 105mm lens, my digital angle of view will be approximately (1.3 x 105mm)=147mm. If shooting with a zoom lens, 50-110mm, you would have a decrease in the wide digital angle of view but an increase in the telephoto end.

 

Full frame 645 camera backs 

IQ280, IQ260, IQ180, IQ160, P65+  Lens factor 1.0

 

49mm camera backs

P45+, P45, P25+, P25 Lens factor: 1.1

 

44mm camera backs

IQ250,IQ140, P40+, P30+, P30, P21+, P21 Lens factor: 1.3

 

36mmx36mm square camea backs

P20+, P20, H20 Lens factor:  1.4

 

36mm camera backs

H10 11MP,  H10 6MP, H101, H5, Lightphase Lens factor: 1.6

 

To calculate the "magnification factor" or the "digital angle of view" the following formula can be used. Divide the film diagonal by the sensor diagonal to create the lens factor.

 

Film Sizes:----------------------------------------Diagonal  

645= 56mm x 42mm------------------------70mm

6x6= 56mm x 56mm------------------------79.196mm

6x7= 56mm x 67mm------------------------87.3212mm

6x8= 56mm x 76mm------------------------94.4034mm

4" x 5"= 100.16mm x 127mm----------161.707mm

 

CCD sizes:---------------------------------Diagonal

Fullf frame=53.9mm x 40.4mm-----------67.36mm

P45/+= 49.1mm x 36.8mm------------61.36mm

P25/+= 48.9mm x 36.7mm------------61.14mm

P30/+= 44.2mm x 33.1mm------------55.22mm

P40+=43.9mm x 32.9mm-----------54.86

P21/+= 44.2mm x 33.1mm------------55.22mm

P20/+= 36.9mm x 36.9mm------------52.1845mm