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 Archive 2012 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?
pompo
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 p.1 #1 · p.1 #1 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?

Does a 80mm contax 645 lens compare to dslr to about 50mm? Or shorter?

What's the formula to get this correct?

Thanks

Apr 04, 2012 at 09:27 PM
mpmendenhall
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 p.1 #2 · p.1 #2 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?

A 645 frame is 6cm wide and 4.5cm high. "Full frame" 35mm format is 36mm wide, 24mm high. The ratio between these gives you the appropriate scale factor: 80mm * (36mm/60mm) = 48mm equivalent horizontal field of view.

Apr 04, 2012 at 09:31 PM
jcolwell
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 p.1 #3 · p.1 #3 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?

When comparing formats with different aspect ratios, (645 = 1.35, 135 = 1.5), I prefer to use the horizontal angle of view (AOV.h). The alternative approach (and most common) is to use the diagonal AOV.d.

Based on AoV.h, the 645 80mm lens is equivalent to a 51mm focal length lens on 135 (35mm) format. Based on AoV.d, it's 50mm. Either way, they're all 'normal'.

The equations are simple trigonometry. You can grab an "equivalent focal length" calculator from my web site, http://www.jcolwell.ca/photography/calc-info/index.htm

Of course, if you put an 80mm 645 lens on a 135 (35mm) or FF DSLR body, it produces the same AoV as does an 80mm 135 (35mm) lens on the same body.

P.S. the typical 645 frame size is 56mm x 41.5mm.

Apr 04, 2012 at 09:48 PM
Mescalamba
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 p.1 #4 · p.1 #4 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?

Its 50mm, but thats just FOV. In theory it "should" be same, but look is different, cause theres magnification and size of sensor/lens.

Only way to get something similar would be 80mm on FF and stitching few photos together (eg. creating bigger sensor). Although even that wont be same, just closer than 50mm on FF.

Apr 04, 2012 at 09:57 PM
pompo
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 p.1 #5 · p.1 #5 · Contax 645 80mm equivalent lenght for 35 mm? 50mm?

thanks everyone

Apr 04, 2012 at 11:03 PM

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