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MF Digital, myths or facts? - MFDBs have better color, truth or myth?

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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?
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Experts's comments
Thanks!
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MFDBs have better color, truth or myth?

Tim Parkin has tested a lot of MFDs and also DSLRs. What he says is that MFDBs have different colors. He finds that the IQ180 is near the top and that he wouldn't touch a P45 with a "barge pole".
This is a P45 image :
While this is from the IQ180:
Tim regards that the Sony Alpha 900 is the one with the best color, see below:
Color is a complex issue that is more about perception than about quantifyable data. All raw converters have widely variable and adjustable color rendition. The figures presented below may be of some interest but I don't think there is sufficient information to draw any conclusions regarding MF having better color is myth or reality.
With exception of the Foveon (owned by Sigma) all pixels are monochrome. Color is added by a color grid array (CGA) in the front of the sensor. So color has nothing to do with sensor design. The raw data contains monochrome data for each pixel and also information on the placements of colors in the CGA. Now, the CGA normally has a "bayer pattern" with RGBG pixels. The spectral response of the R, G and B pixels may vary. The raw file also contains information on how to convert the monochrome information into color.
The CGA implementation may vary between vendors. It is feasible that some vendors would opt the CGA design for high ISO while others may opt for good color separation. On the other hand, a CGA optimized for good color separation may be bad at separating subtle color nuances. Compare this to Velvia in the old times. Velvia had excellent color separation, and low ISO but was not very good at properly handling subtle colors.
The two spectral diagrams below are from an excellent article on camera color from DxO-mark, available here.
To the left we have Canon EOS 500D to the right Nikon D5000.


The image below shows the color response of the Dalsa_FTF9168C which may or may not be used in the IQ160.


On the Dalsa chip the red channel is the most sensitive one, but the overlap bettween red and green is more similar to the Nikon camera shown above than to the canon. Neither is even close to the sensivity of the human eye (linked from Norman Koren's webpage):


So, let's just find that sensors are different. In human vision color really arises in the brain as a result of complex processing. In digital cameras color is created in raw conversion and the subsequent processing.


Good color, accurate color and pleasant color


We don't know how many colors the human vision can tell apart. I have seen figures between 200 000 and 20 000 000. The normal standard in the photographic industry is the Xrite color checker. This contains 24 color patches. We can check how two cameras these 24 colors:


In the figures below the out frame is camear color, while the inner frame i reference color with and without luminance correction.

Hasselblad H4DIII50 below:



Nikon D800E below


Another representation is the a*b* diagram given below:



With the corresponding data for the Nikon D800E below


The measured data above actually indicates that the D800E is better in reproducing a color checker card under a given set of conditions. The main difference between the Hassy and the D800E was that the Hassy image processed in LR4.2 was significantly oversaturated. When processing in LR4.2 I pulled back 13 units of saturateion on the Hassy and 4 units on the Nikon. Delta E is about half on the Nikon.


I have no first hand experience with MF, what I write is a drill down based on reading and looking at files available on the net. Still I have seen a couple of direct comparisons of Digital MF and DSLRs and got the impression that Digital MF camera had better color. This thread on LuLa forums is a good example.




Last Updated on Thursday, 13 December 2012 11:56  

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