"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions thread
Lost in Time
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Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
In reply to walkaround, Apr 27, 2013

The summary: an f/1.4 lens on a m4/3 camera acts like an f/2.8 lens on a 35mm camera for the purposes of framing and depth of field only. For exposure and "final brightness", "total light", prints or any other visual idea you want to throw in there, it acts like what it is: an f/1.4 lens.

Of course it does. If I take two difference formats and set the same framing, subject/lighting, f-stop and ISO, I will get exactly the same shutter speed.

However, this is precisely because this is how ISO is defined. The FF camera really does receive 4x the light of the u4/3 camera, each pixel being 4x larger and hence gathering 4x the light, and hence having 4x the signal/noise. What this means is that although the settings are the same, the FF camera will show less noise than the u4/3 camera, just as the u4/3 camera shows less noise than a P&S at the same ISO. I don't think anyone here would claim that the noise level on u4/3 is the same as a FF camera at the same ISO, just as no one would claim that the u4/3 noise is the same as a P&S at the same ISO.

The curious thing is that this means that if you stop-down the FF lens to give the same DOF as u4/3, and boost the ISO to maintain the same shutter speed, you end up an identical image in terms of DOF and image noise. This is what is meant by 'equivalence': there is no magical advantage to either FF systems if the cameras are correctly set so that the resulting images would be truly identical.

In reality, none of this matters: you choose the format and lens for the subject you want (and hopefully something more interesting than the pink mess at the start of this thread, which completely misunderstands the entire concept of equivalence as the images have obviously different DOF...).

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