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Demosaicing algorithms

Doug Kerr

Well-known member
"We" often point out that one of the advantages of working with the raw output of a camera is that we have the opportunity to employ different demosaicing algorithms, perhaps those that perform better (maybe especially in some particular situation) than the one used for in-camera development.

But we don't hear much about people actually exploiting this flexibility. On the other hand, most of the raw development tools don't really give us a choice. So we have to hope that the one they use is "better" than, for example, the one used in ACR. Or that the one used in ACR is "better" than the one used in our camera.

I have over the last few days looking at the raw development program Raw Therapee, and one of the first things I noticed was that it offers a choice among ten demosaicing algorithms, and for each of them, a choice of a parameter identified as "number of false color suppression steps". It is discussed here in part of the Raw Therapee holy writ (the RawPedia):

http://50.87.144.65/~rt/w/index.php?title=Demosaicing#False_Color_Suppression_Steps

The default algorithm there is designated in the menu "amaze"; I find out that its real designation is AMaZE (Aliasing Minimization and Zipper Elimination).

I looked about for some discussion, pertinent to our context, of the pros and cons of different available algorithms, and found this very nice article:

https://johnwiddall.wordpress.com/2014/02/06/raw-processors-which-demosaicing-method-part1/

Best regards,

Doug
 

Andrew Stannard

pro member
HI Doug,

Thanks for researching this matter and providing some links. Although I primarily use Lightroom for my processing I do also play around with Raw Therapee occasionally. Have tried a few of the different de-mosaicing algorithms, but good to now understand a little more about what they do.

Recently I have switched to using a Fuji X100T, which uses Fuji's X-Trans arrangement, rather than the traditional Bayer. I may have a another look at Raw Therapee and see whether the options presented are different for the X-Trans Sensor.

Regards,
Andy.
 

Doug Kerr

Well-known member
Hi, Andy,

HI Doug,

Thanks for researching this matter and providing some links. Although I primarily use Lightroom for my processing I do also play around with Raw Therapee occasionally. Have tried a few of the different de-mosaicing algorithms, but good to now understand a little more about what they do.

Recently I have switched to using a Fuji X100T, which uses Fuji's X-Trans arrangement, rather than the traditional Bayer. I may have a another look at Raw Therapee and see whether the options presented are different for the X-Trans Sensor.

Yes. In its demosaicing panel, there is a separate section for the X-Trans sensor, offering three choices (not the same as for a Bayer sensor) plus the usual setting for the number of false color suppression steps.

Best regards,

Doug
 

Andrew Stannard

pro member
Hi,

Have just downloaded the latest version of Raw Therapee for a little play. For a free program you really can't fault it. It has an outstanding set of options - more so than Lightroom/ACR or any other programs I have tried.

It has what I might call an 'Engineers Interface' rather than a photographers interface, but then I'm an engineer, so that's not a bad thing :)

For the XTrans sensor I would say that RawTherapee manages to extract a little more detail that ACR/Lightroom, but I fear my Lightroom workflow is too entrenched for me to make a switch. I'm very happy with the quality of 24"x16" prints from my X100T, which is enough for me, but it will be interesting to see if Adobe plays catch up on de-mosaicing XTrans sensors in later versions.

Regards,
Andrew.
 

Doug Kerr

Well-known member
Hi, Andrew,

Hi,

Have just downloaded the latest version of Raw Therapee for a little play. For a free program you really can't fault it. It has an outstanding set of options - more so than Lightroom/ACR or any other programs I have tried.

It has what I might call an 'Engineers Interface' rather than a photographers interface, but then I'm an engineer, so that's not a bad thing :)

Indeed!

For the XTrans sensor I would say that RawTherapee manages to extract a little more detail that ACR/Lightroom, but I fear my Lightroom workflow is too entrenched for me to make a switch.

I understand.

I'm very happy with the quality of 24"x16" prints from my X100T, which is enough for me, but it will be interesting to see if Adobe plays catch up on de-mosaicing XTrans sensors in later versions.

Yes, that will be interesting to see.

Glad you enjoyed your encounter with Raw Therapee.

Best regards,

Doug
 
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