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MF Digital, myths or facts? - Do MFD have better DR?

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Article Index
MF Digital, myths or facts?
Collecting more photons
Comparing the top of the line MF back with the top of the line DSLR
Is Capture One better on IQ180 files?
A larger format is less demanding of the lens
The Really Right Stuff
OLP (AA) filtering
The 16 bit issue, truth or myth?
Do MFD have better DR?
MFDBs have better color, truth or myth?
Flexibility
Summary and conclusions
Are large pixels better?
Read also
Experts's comments
Thanks!
All Pages
Do MFDBs have better DR than DSLR?

The 16 bit issue is related to DR. DR essentially tells about distance from maximum undistoreted signal to the noise floor. In photography it's practical to measure it in EV (f-stops). DR = log10((FWC/ReadoutNoise))/log(2).


Here, FWC is full well capacity, the number of electron charges each pixel can hold, and readout noise is measured in electron charges.


We have seen before that DR for the best DSLRs is approaching 14EV while it is more like 11.5 EV for the leading digital back. The reason behind this is the todays best CMOS sensors have incredibly low readout noise. On the other hand especially Canon cameras fail to make use of the full dynamic range of their sensors, due to off chip digital readout.


Dynamic range is obvious if we expose to the right (that is fully utilize FWC) and look at shadow detail. A sensor with a wide dynamic range would be able to produces good detail in the darkest darks. If we reduce exposure, hiking up ISO, we would still be able to produce high quality images. A sensor with excellent dynamic range would excel at high ISO.


Now, Canons have a weakness in dynamic range but excel at high ISO. How do they do it? The answer seems to be that Canon's CMOS sensor has excellent dynamic range, but the camera cannot handle. So when high ISO is set the signal is preamplified so readout noise can be reduced but FWC cannot be any longer fully utilized.


Anoher mythical property of MFDBs is better handling of highlight clipping. I have significant doubts in this regard. Both CCDs and CMOS are linear devices and they should behave pretty identically when going into saturation.


I'm not really sure about the importance of DR. It is important for sure, but I don't see it as the most important parameter.








Last Updated on Thursday, 13 December 2012 11:56  

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