# Three geeks.

Started Jul 31, 2014 | Discussions thread
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Three geeks.
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The first geek says:

50mm f/2 1/100 ISO 400 on mFT is equivalent to 100mm f/2 1/100 ISO 400 on FF because it has the same [diagonal] angle of view and exposure.

Someone asks him, "What about DOF, diffraction, and noise"?  He answers, "The DOF is deeper with mFT, so that's a plus, the diffraction is less with FF, but who cares, and the noise is probably more, depending on the sensor, but it's low enough with mFT that it's not important unless you're taking pics of black cats in coal mines."

The second geek says:

50mm f/2 1/100 ISO 400 is equivalent to 50mm f/4 1/25 ISO 400 because they have the same framing and exposure.

Someone asks him, "What about DOF, diffraction, noise, and motion blur?"  He answers, "All different, but that won't matter if the whole scene is within the DOF, there is no motion in the scene, and it's printed at 8x10 inches".

The third geek says:

50mm f/2 1/100 ISO 400 on mFT is equivalent to 100mm f/4 1/100 ISO 400 on FF because it has the same [diagonal] angle of view, the same DOF for a given perspective, framing, and display size, the same diffraction, the same total amount of light projected on the sensor, the same motion blur, and the same brightness.

Someone asks him, "What about the exposure and noise?"  Well, the exposure for the FF photo is 1/4 the exposure as the mFT photo because the same total amount of light is distributed over 4x the area.  The noise, however, would be more or less the same if the sensors had more or less the same efficiency.

The first two geeks then argue furiously with the third geek, saying that he's trying to make the term "equivalent" something that it's not.

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