Happy New Year Voigtländer ! (25mm 0.95, 35mm 1.4 @ 50mm 1.1 with GH2 !, 1st part : t

Started Jan 1, 2011 | Discussions thread
Joseph S Wisniewski
Forum ProPosts: 33,930Gear list
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The dreaded word "equivalence"
In reply to Uwe Steinmueller, Jan 2, 2011

Uwe Steinmueller wrote:

because 25mm f0.95 on four thirds is equivalent to 50mm f1.9 on full frame

Why f/1.9? It is still a 25mm f/0.95 with the angle of view of a 50mm on full frame.

With the angle of view and the depth of field and the light gathering capability of a 50mm f1.9 on full frame.

Remember, Seb is doing a shallow DOF exercise. Let's check DOFmaster.com. At 10 feet, we have...

  • 50mm f2.0 on FF = 1.45ft

  • 25mm f1.0 on 4/3 = 1.46ft

(I'd put the 0.01 foot down to them not having the diagonals right to withing 0.25%).

And those are both 25mm "holes in space" and will gather exactly as many photons on the same trajectories (same "angle of view" = same ray tracing).

Yes, capturing the same number of photons means if you were shooting the 4/3 at ISO 100, you'd need to shoot the FF at ISO 400, but strangely enough, that's exactly how the sensor sensitivities line up.

That's the downfall of the smaller formats, it takes more and more exotic lens designs to get to the same amount of light. The 43.3mm image circle is sort of a "sweet spot" for humans our size on a planet with an abundance of glass.

The strength of the small formats is slower lenses, which tend to be very high quality and fairly compact.

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Rahon Klavanian 1912-2008.

Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.

Ciao! Joseph

http://www.swissarmyfork.com

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