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UniWB Link -- (and what about Monochrome??)

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Peter Forsell:

--- Quote from: Shane on October 01, 2015, 20:21:18 ---And that is when the original RAW data is saturated. Either RAW data is "blown" or it isn't, there is no in between.
--- End quote ---

This is an important distinction. Capture NX-D (similarly NX2 before that) shows data as blown sometimes about 0.5 stops too early. This is frustrating, since Capture cannot "recover" even this unblown data but insists it is blown.

Lightroom seems to go wrong to the opposite direction by doing behind-the-scenes highlight recovery when opening a file, even when no recovery has been asked -- and LR represents blown data as not-blown.

For these reasons I gave up on Nikon Capture a decade ago but have been doing a test with every new release. All in vain ... looks like it is incurable. Lightroom's workflow on the other hand would fit my work style, but the undisclosed data massaging bothers me.

Rawdigger and/or FRV show the true raw data but regrettably both 1) cost extra and 2) are difficult to integrate seamlessly into my workflow.

Andrea B.:
I highly recommend Raw Digger. It is well worth the cost to learn how your camera actually records.

*******

Meanwhile, on with my UniWB experiment......
I've created my red, green and blue TIFs and have the Excel spreadsheet set up.

Equipment: 
Nikon D810 + 70-200/4G AFS VR
f=8.
Focal length=100mm.

Settings:
ADL=Off.
WB=Auto1. (Shooting raw so WB can be auto.)
Space=sRGB. (Keep everything in gamut. Well, R/G/B should always be in gamut anyway.)
ISO=64. (Base setting to minimize noise.)
Picture Control = Flat[0]. (Reduced contrast improves the accuracy of the in-camera histogram.)

White Balance
Average values from the R, G and B shots were entered in the Excel spreadsheet.
In PS Elements 11 a Magenta (225,111,193) file was created for monitor display.
I now made the in-camera WB against the big Magenta screen.
Given that I was using a Nikon, this did not happen on the first try.
But eventually I got the D810 to declare a WB against the Magenta screen as "good".

However --- The Magenta UniWB shot shows RGB coefficients of .92, 1.0, .63.
Red is in the ballpark but slightly low. Blue is very much off.

So I did not quite attain a UniWB on this first attempt.
I know the methodology is sound. (I've hand calculated this stuff in the past.)
Possible errors:

* I'm thinking that the difficulty I had with the D810 in-camra WB likely contributed to the problem?
* And/or maybe there was too much ambient light when I performed the WB against the magenta screen?
* I probably overexposed the R, G and B shots? Not supposed to use ETTR until after setting up UniWB. "-)[1,2,3] Raw Digger Screen Shots
I used a sample from the brightest area.

[4] Magenta (225,111,193) File for One-step WB
Created in PSElements.

[5] Excel Spreadsheet
Note the Coefficients column has a bad Blue value.

[6] UniWB Shot #1 with Flat[0] pic control.
Although I did not produce unitary RGB coefficients in my first attempt this shot looks very green. :-)

[7] UniWB Shot #2 with Std[4,3,1,0,2,0] for [sharpening,clarity,contrast,brightness,saturation,hue]
Still looking very green.

Shane:

--- Quote ---Possible errors:

    I'm thinking that the difficulty I had with the D810 in-camra WB likely contributed to the problem?
    And/or maybe there was too much ambient light when I performed the WB against the magenta screen?
    I probably overexposed the R, G and B shots? Not supposed to use ETTR until after setting up UniWB. "-)
--- End quote ---

I found it best to use a fixed F/L lens (note your shots are at 100/78/100mm f/l)
Define your manual exposure characteristics and don't change them between shots.
Watch the ambient light issue.
None of your exposures are O/exp (check your Rawdigger results) if anything they are a little on the low side.
Your Blue value is probably off due to underexposure of the B channel (too much noise).
The first time I used this method my exposures were a little low (similar to yours), increasing the exposure but without saturation will probably solve your problem.

I have notes on the issues somewhere but, as usual, put them somewhere safe! I will see if I can find them.

Andrea B.:
Thanks, Shane. I did not even see that I shot green at 78mm instead of 100mm. Not sure how I managed to do that!!! "-)

I'll try again later when there is no grey light coming in thru the windows. (We are having horrible hurricaney weather.)

Shane:
When I build a custom UWB using the monitor I usually do this in the evening with the room lights off. No glare and no reflected colour casts.

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