As every camera geek with too much time and on the search the perfect sensor I came to the point of how to compare noise, dynamic and other significant points.
One thing that confuses a lot of people who are not that familiar with the matter is that the preview on the camera back, which also includes a histogram, and widely recognized as THE method to judge an exposure is misleading.
The problem with this workflow for everyone who uses .raw exclusively is that those informations are flat out wrong - histograms, clipping warning, fullscreen preview all of those are calculated based on the jpg generated by the camera not the real information captured in the .raw file.
If we use autoWB in the camera and a picture preset other than neutral this preview is skewed in a way that is non determined and totally up to the automatics in the camera - which can, and will fluctuate from shoot to shoot even when noting changed in the frame...
The solution can only be that the informations are calculated by using the .raw image file but that is up to the manufactures and agains the current trend of more megapixels because a calculation on the ever rising pixel count takes more and more time in which the camera could seem not responding to user input which is nothing a manufacture would want.
This spawned a work-around: uniWB or Unitary White Balance
With this method the preview jpg will be mangled in a way to represent what the sensor really saw while capturing the image. It functions in a way that cancels the camera internal processing as good as possible. For everybody who wants to read more about the technical aspects of it I kindly point to Guillermo Luijk: http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm
To put it simple it works by crafting a special color which will yield a grey .raw picture ones one sets th WB by using this color.
After reading a couple of sites I was interested in this method and determined to use it for my new camera - which at this point was decided to be the Nikon D800. Unfortunately there was no one who has made such a WB preset available on the net.
So it was my time to give something back and after reading the technical informations I could find on that topic for the secind or third time I started my search for the uniWB.
After about two hours I was pleased with the result I got which came close to the perfect color balance - R=G=B.
The color that produced the result was a darkened red - which also solves the mystery why our camera see dark reds not as we see it, it results in a grey red-ish tinted color when processed.
Using this color to set the white balance and pushed through the camera internal jpg engine produces color multiplicators of R=1.011719; G=1.000000; B=1.007812 - which is a deviation of ~1.17% on the red channel.
And after all this here is the .raw file everybody was waiting for:
https://www.dropbox.com/s/ng2xrivx6on6n9c/uniWB.NEF (39mb!)
The use of this file is really simple:
To maximize the effect use the neutral picture preset with sharpening, saturation, hue and contrast all set to 0 as those also do effect the jpg preview and thus the histogram. The whole process is a trade-off but lets you squeeze out the last bit of performance from your sensor which comes in really handy in high contrast situations with saturated blue and/or red channels (especially landscapes) as those are more accurately represented in the resulting histogramm on the camera's back.
A lot of sites that are dealing with this topic also tell you not to use active D-lighting - I kind of doubt that it does effect the use of uniWB because ADL is changing the exposure before taking the picture which has the same effect as if you were doing so manually - but keep in mind if you encounter results that you are not expecting if might be a possible point of failure, if that happens just turn ADL off.
One thing to remember is that you buy the more accurate preview and histograms by another step while editing the pictures - you have to set the white balance to something that suits your taste. You could use a preset on import to Adobe Lightroom so that is not really a problem but another point to consider.
If you use uniWB during a paid shoot and have a client that wants to see some images while on set you might get a strange, questioning look from them because all your previews in the camera will have a greenish tint. In a controlled environment like that you might want to meter the white balance and set it accordingly just to avoid the hassle...
One thing that confuses a lot of people who are not that familiar with the matter is that the preview on the camera back, which also includes a histogram, and widely recognized as THE method to judge an exposure is misleading.
The problem with this workflow for everyone who uses .raw exclusively is that those informations are flat out wrong - histograms, clipping warning, fullscreen preview all of those are calculated based on the jpg generated by the camera not the real information captured in the .raw file.
If we use autoWB in the camera and a picture preset other than neutral this preview is skewed in a way that is non determined and totally up to the automatics in the camera - which can, and will fluctuate from shoot to shoot even when noting changed in the frame...
The solution can only be that the informations are calculated by using the .raw image file but that is up to the manufactures and agains the current trend of more megapixels because a calculation on the ever rising pixel count takes more and more time in which the camera could seem not responding to user input which is nothing a manufacture would want.
This spawned a work-around: uniWB or Unitary White Balance
With this method the preview jpg will be mangled in a way to represent what the sensor really saw while capturing the image. It functions in a way that cancels the camera internal processing as good as possible. For everybody who wants to read more about the technical aspects of it I kindly point to Guillermo Luijk: http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm
To put it simple it works by crafting a special color which will yield a grey .raw picture ones one sets th WB by using this color.
After reading a couple of sites I was interested in this method and determined to use it for my new camera - which at this point was decided to be the Nikon D800. Unfortunately there was no one who has made such a WB preset available on the net.
So it was my time to give something back and after reading the technical informations I could find on that topic for the secind or third time I started my search for the uniWB.
After about two hours I was pleased with the result I got which came close to the perfect color balance - R=G=B.
Using this color to set the white balance and pushed through the camera internal jpg engine produces color multiplicators of R=1.011719; G=1.000000; B=1.007812 - which is a deviation of ~1.17% on the red channel.
And after all this here is the .raw file everybody was waiting for:
https://www.dropbox.com/s/ng2xrivx6on6n9c/uniWB.NEF (39mb!)
The use of this file is really simple:
- Take a picture with your D800/E
- Use a SD or CF card reader to copy the uniWB.nef onto the card
- Rename uniWB.nef according to the picture you just took (increment the counter by one on the uniWB.nef)
- Put the card back in the camera and use the menu item 'white balance' set to 'PRE' and choose the grey uniWB.nef file you just copied
To maximize the effect use the neutral picture preset with sharpening, saturation, hue and contrast all set to 0 as those also do effect the jpg preview and thus the histogram. The whole process is a trade-off but lets you squeeze out the last bit of performance from your sensor which comes in really handy in high contrast situations with saturated blue and/or red channels (especially landscapes) as those are more accurately represented in the resulting histogramm on the camera's back.
A lot of sites that are dealing with this topic also tell you not to use active D-lighting - I kind of doubt that it does effect the use of uniWB because ADL is changing the exposure before taking the picture which has the same effect as if you were doing so manually - but keep in mind if you encounter results that you are not expecting if might be a possible point of failure, if that happens just turn ADL off.
One thing to remember is that you buy the more accurate preview and histograms by another step while editing the pictures - you have to set the white balance to something that suits your taste. You could use a preset on import to Adobe Lightroom so that is not really a problem but another point to consider.
If you use uniWB during a paid shoot and have a client that wants to see some images while on set you might get a strange, questioning look from them because all your previews in the camera will have a greenish tint. In a controlled environment like that you might want to meter the white balance and set it accordingly just to avoid the hassle...
Danke Dir, Markus!
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