G6 vs newest sensors: Real difference in high ISO noize

Started 6 months ago | Questions thread
Anders W
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Re: G6 vs newest sensors: Real difference in high ISO noize
In reply to Øyvin Eikeland, 6 months ago

Øyvin Eikeland wrote:

Ulric wrote:

Øyvin Eikeland wrote:

The logic behind my original thought was that since olympus only utilise part of the range of the sensor, the numerator (signal) in the signal-to-noise ratio fraction needs to be reduced.

There is no way to know that they only utilise part of the range of the sensor without knowing what the scene looks like.

Ok,

I get that. I put in this prerequisite earlier in the thread:

"_IF_ I assume that you do not want or need the extra headroom that the Olympus E-M5 provides. I then take that you can disregard the extra dynamic range above the clipping point of a "vanilla" camera where ISO 12800 actually is measured to ISO 12800."

The reason why I want to do this excercise is to make it easier to compare the G6 (which exposes almost like a "vanilla" camera to the E-M5 which under-exposes quite a bit. For myself I have coined the phrases "usable SNR" and "usable DR". This terms only makes sense _if_ the scene you are taking a picture of does not contain any bright spots that would cause a "vanilla" camera (like the G6) to go into clipping. I got some help from Anders W (thanks!) to get the formulas right and produced these graphs using libreoffice:

SNR=MeasuredSNR-log2(ManufacturerISO/MeasuredISO)*3.01

DR=MeasuredDR-log2(ManufacturerISO/MeasuredISO)

I understand that some will think of this as nonsense but I think the above graphs are useful to try and understand how much worse the G6 is compared to the latest generation of sensors for low-light photography. The difference to the E-M5 (using this method) is 1dB SNR at ISO3200 and 1.88dB SNR at ISO6400. The difference in DR (using this method) is 0.5 stops at ISO3200 and 0.8 stops at ISO6400. Going above ISO6400 seems like a bad idea for any MFT camera...

Feedback is welcome. I can even accept some bashing if I am too far astray

Best regards,

ØE

I didn't try to check whether you got the numbers right but it looks pretty reasonable to me. What you are effectively comparing now is what happens if you set the cameras to the same camera ISO and expose them identically (assuming that none of them clip, which in turn implies that you'll be leaving about one EV of unused headroom with the E-M5).

Be aware though, that this is not always the optimal way to use them and thus to compare them. For example, if you are shooting RAW and are leaving one stop of unused headroom with the E-M5 at a camera ISO of 200, a better solution is to increase the ISO to 400 since that will lower read noise significantly on this particular camera. If you look at the DxO graph for DR with "measured ISO" on the x-axis, you will see that the E-M5 is now nearly one EV ahead of the two Panys rather than just barely ahead as in your graph.

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