"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions thread
Great Bustard Forum Pro • Posts: 40,694
Re: An answer:

Olymore wrote:

Okay, from your last response to my question about maximising DOF and DR I either haven't understood correctly or...

what you mean is that for the FF camera you can get the same DOF and potentially an additional stop of DR by using a slower shutter speed (assuming that's a viable option) .


Your comment earlier where you said "for Equivalent photos, the FF sensor would collect the same amount of light, but the read noise would still be twice as much, so the ratio of the saturation limit to the noise floor would be have as much, and thus one stop less DR"

Correct, based on a FF sensor being made of the same pixels as the mFT sensor.

So if an equivalent photo (presumably using 2 lower F-stops to achieve the same DOF and receiving the same light as an M43 sensor) results in 1 stop less DR at the same shutter speed for sensors of the same efficiency /pixel density...

A FF sensor made of the same pixels as an mFT sensor would not be the same efficiency (they would have the same QE, but not the same read noise / µphoto -- it would be twice as high, which would not be an issue except in dark shadows, keeping in mind that the higher the ISO, the more of the photo that is actually shadow, just with brightening applied by the higher ISO setting -- see gollywop's excellent article).

...how can a FF frame camera then have more DR when you want to maximise DOF in a landscape photograph unless you lower the shutter speed by 2 stops to increase the total light to 2 stops more than the M43 sensor ?

If the sensor is more efficient.  The Canon 6D sensor is slightly less efficient than the EM5 sensor at low ISOs, and equally efficient at higher ISOs.  The D800 sensor is more efficient at low ISOs, and slightly less efficient at high ISOs.

I'll browse your equivalence  tomorrow for an answer as it's late here

Many criticize Equivalence saying that things don't work this way in the real world.  They ignore the conditions of noise / DR equivalence, which requires equally efficient sensors.  The further apart are in efficiency (keeping in mind that the sensor efficiency depends on the ISO setting for many sensors due to differences in read noise), the less exact noise / DR equivalence will be.

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