Color Balance

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Marpel
Posts: 317
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Color Balance

Postby Marpel » September 27th, 2016, 10:49 pm

I recently processed a few images that I took while on a hike (Joffre Lakes chain in B.C. if you ever get a chance, they are absolutely spectacular). Part of the hike was quite socked in with fog and because it was quite early, it was also a bit on the dark side. As most of those early morning images had some blue cast to them, I did some colour balancing as one of the steps.

Out of curiosity, I did the same basic auto color balance in three different programs (PWP, NX2 (might be NXD or whatever Nikon's latest is), Photoshop) and was surprised at the marked difference in the results of the three programs. I, however, discovered that PWP appeared to come out the best. My first question is, was that just luck of the draw or does each program use a different algorithm/process to do auto balance?

I also tried PWP manual balance, using the probe applied in the fog area, and this proved to be the best of all attempts. This leads to my second question of, Is there any benefit to changing the size of the probe from its default 3x3 down to 1x1 or up to as high as 9x9.

My third question is, as I use NX2/NXD or whatever, to first process my RAWs and as its colour balance does not seem to give me the best result, is there an appreciable downside to doing colour balance in PWP (on 48 bit TIFF) after the RAW processing? It seems logical to me to do Colour Balancing as the first step in the RAW process, but certainly prior to any change in exposure.

Thanks,

Marv

doug
Posts: 86
Joined: April 24th, 2009, 10:06 am
What is the make/model of your primary camera?: Nikon D-500
Location: Toledo, Ohio USA

Re: Color Balance

Postby doug » September 29th, 2016, 9:54 am

OMG, Marpel. Thank you for posting this.
The Color Balance transformation is more mysterious to me than almost any other transformation that I use frequently. (Certain others are mysterious too. But I don't use them so frequently).

I am particularly interested in the last question you posed. I bugged Jonathan and Kiril to update PWP to accommodate raw processing for my new Nikon D500. Then after finally getting that capability, I have subsequently gone another way. I want to work in 16 bits (48 bits?) but I just couldn't seem to come up with initial PWP raw converter settings that would consistently give me a starting point that I liked as much as the OOC JPEG. (I have my camera settings at the most neutral possible in terms of sharpening, contrast, etc. because I want to reserve maximum flexibility for post.)

So now I am using Nikon's NX-D raw converter to generate a converted raw image that reflects the OOC Jpeg look. Then I don't usually do any other processing there (I hate the user interface) and immediately convert the result to a 16-bit tiff which I take into PWP for all further processing. But like your last question, I leave any color correction or adjustment for PWP.

I have been assuming that unless the color balance is way off in left field (like, for example, shooting in full sun with the WB set for flourescent), the tiff has retained enough of the information I'll need to tweak the color in PWP a minor amount and I wouldn't achieve a noticeably better result if WB were adjusted before leaving the raw converter.

If this turns out to be true, like you, I still would like to unravel some of the Color Balance transformation characteristics that remain somewhat mysterious to me. One thing that Den taught me recently (because I really like the temperature slider that exists in PWP's raw converter) is that the Color Balance transform does include a temperature slider if you dive down deep enough.

jsachs
Posts: 1213
Joined: January 22nd, 2009, 11:03 pm

Re: Color Balance

Postby jsachs » September 29th, 2016, 6:45 pm

Auto white balance involves guessing the white point of the image, and there is no definitive way to do this. PWP averages the color of the lightest pixels, but it can be fooled, for example, by white specks such as clipped highlights in the image.

The idea behind color balance is fairly simple, namely to let you remove or intentionally add color casts. Sometimes the correction that works best for highlights does not work as well for midtones or shadows, so the transformation provides for adding or removing different color casts from different parts of the tonal range. By default, PWP does auto white and black balancing, but you can create additional corrections for intermediate values. Usually the easiest way to remove casts is to click on an area of the image that should be neutral, but you can also specify color casts to add or remove manually via the color picker. The end result of specifying a set of color balance corrections is to create curves applied to the red, green and blue channels of the input image, and these curves are displayed in the transformation dialog box.

There is a detailed description with examples of this transformation in the Color Balance.pdf white paper which you can download from our web site. If you have any questions that are not answered there, please post them.
Jonathan Sachs
Digital Light & Color

Marpel
Posts: 317
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Color Balance

Postby Marpel » September 29th, 2016, 11:42 pm

Doug and Jonathan,

Thanks for your replies.

I actually read the noted white paper prior to my first post. I think I understand the concept and reasons behind colour balancing an image, however, I wished to clear up a few points.

The white paper states "colour casts can arise from many different causes....how the image was captured and processed". It later suggests that colour balancing be done as the very last step "it is obvious to correct the problem at the end of the process".

Can you confirm exactly where you suggest this part of the processing be done, including whether you prefer in your workflow to do it in RAW processing or later when the image is a 48 bit TIFF, or does it really matter at all whether it is at the RAW or TIFF stage?

And a last, rather trivial, question, in the manual method with using the eye dropper to choose a neutral location, is there any reason to choose a 1 x 1 size or 9 x 9 or just leave it at the 3 x 3 default?

As previously stated, I have found that PWP most often gives me the best White Balance between three image processing programs, so I will continue to do that in PWP. I'm just trying to determine exactly when in the processing to do it and if I am missing the boat by not doing it in the RAW processing. I currently do the very basic first steps of processing my RAWs in Nikon NX-D, then do further stuff in PWP on the 48 bit TIFFs (Although I turn off all sharpening in NX-D and use Focus Magic between NX-D and PWP).

Thanks again,

Marv

jsachs
Posts: 1213
Joined: January 22nd, 2009, 11:03 pm

Re: Color Balance

Postby jsachs » September 30th, 2016, 6:03 am

I currently find myself color balancing more at the beginning than at the end of the process, especially before adjusting saturation or making other color corrections, but in most cases the order of operations doesn't really make much of a difference unless you are making very large corrections. You can color balance during RAW conversion if you prefer color temperature/tint sliders to the controls in the Color Balance transformation. As with any transformation, working with 48-bit color is of course preferable to working with 24-bit color.

The reason for using a larger probe is to average over a larger patch of the image when determining the color to add or remove. A smaller probe can zero in on smaller features, while a larger probe is less sensitive to noise or other local variations.
Jonathan Sachs
Digital Light & Color

doug
Posts: 86
Joined: April 24th, 2009, 10:06 am
What is the make/model of your primary camera?: Nikon D-500
Location: Toledo, Ohio USA

Re: Color Balance

Postby doug » September 30th, 2016, 10:15 am

Marv ...
If I have interpreted Jonathan correctly, it sounds like there is no significant detriment to the effectiveness of color balance adjustments under the process that you and I are pursuing. Namely, convert the Nikon nef raw file in Nikon's own NX-D converter which applies the camera's jpeg picture control settings to the rendered result. Then, without any further adjustments in that software, save the rendered result as a 16-bit (48 bit) tiff and conduct all further editing (including color correction) in PWP. Jonathan did make a distinction between working with 48 bit vs 24 bit files, but didn't highlight a particular advantage to conducting such edits while still at the raw converter stage of the process.

He did mention that working with PWP's raw converter allowed you to work with color temperature/tint sliders "if you prefer such controls". (Which I do like) But that seemed to pertain more to the style of editing interface than to suggest that conducting the color balance adjustment at that point in the process produces a more effective outcome. If that is an incorrect interpretation, I hope he will clarify.

I do like using a temperature slider. And that was one of the things I passed up when I grudgingly concluded that I just couldn't seem to develop PWP raw converter settings that consistently produced as pleasing a starting point rendering as I could automatically achieve with Nikon's software whose raw rendering reflected the in-camera picture control settings.

If someone could describe how to develop starting point settings for PWP's raw converter that duplicate what I achieve automatically with Nikon's converter, that would be the best of all worlds.

Doug

ksinkel
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Re: Color Balance

Postby ksinkel » September 30th, 2016, 11:52 am

In my experience, the practical way to set color balance In the raw converter is:

First set White Balance to Camera WB. (You can make this the default setting under File/Raw Settings.) This adjusts white balance to the lighting conditions your camera detected. This is usually pretty accurate.

Second, if you are not satisfied with this balance, use the color probe on a neutral point to refine it. When using the probe, I will usually try a number of different points. The points may be different portions of the same object, such as different sections of a cloud for instance or different points in entirely different parts of the image, such as an article of clothing that you think should be neutral and a subject's teeth. By using the Undo button between tests with the probe, I can quickly sample a number of different options and settle on the one I like best.

These two methods suffice for most images. However in unusual cases, if I feel either of the two above methods still need further improvement, I use the best result as a starting point for the temperature and tint controls. When I use the controls, I tend to make small adjustments to refine the settings obtained above. Again, I use Undo to get back to a known starting place when trying different adjustments.

One last thought -- to compare options side by side, you can use the Apply button to create a fully processed image of a particular adjustment while still keeping the raw dialog open for further experimentation. This is a slow process of course, so I only use it when I really can't make up my mind otherwise.

Kiril
Kiril Sinkel
Digital Light & Color

doug
Posts: 86
Joined: April 24th, 2009, 10:06 am
What is the make/model of your primary camera?: Nikon D-500
Location: Toledo, Ohio USA

Re: Color Balance

Postby doug » September 30th, 2016, 2:25 pm

Thanks, Kiril ...
If you thought my earlier message meant that I was having a problem getting WB in PWP's raw converter to match the jpeg-like output I achieve with Nikon's converter, that's not what I was mainly referring to. Rather, it is the highlight, shadow and midtone adjustments that I need to fiddle with to keep the rendering from being on the dark side and very bland. But unfortunately the settings that seem to be right for one image don't seem to be just right for the next.

Dieter Mayr
Posts: 450
Joined: April 24th, 2009, 11:47 am
What is the make/model of your primary camera?: Nikon D700
Location: Salzburg / Austria

Re: Color Balance

Postby Dieter Mayr » October 1st, 2016, 4:49 am

To my knowledge, the WB setting in the camera doesn't affect the RAW file at all, so it is of no importance to what it is set, other then how the image on the monitor of the camera looks like.
I prefer to have it set to "Cloudy", so I have a fixed reference.
When using Capture NX-D I chose the WB setting that looks best to me, export as 16 bit TIF and make fine corrections in PWP.
May usual general workflow in PWP:
Crop _ Anything that I don't want in the final picture should be away for any auto settings.
White balace - Giving a try with auto, often it is good, often it kills that warm light in morning or evening that I like.
So mostly a slight correction, if any is mostly enough for me.
Then anything else like contrast, selective corrections, sharpening

Dieter
Dieter Mayr

doug
Posts: 86
Joined: April 24th, 2009, 10:06 am
What is the make/model of your primary camera?: Nikon D-500
Location: Toledo, Ohio USA

Re: Color Balance

Postby doug » October 1st, 2016, 9:29 am

Thanks, Dieter ...
I agree with you that my understanding is that the camera WB settings do not affect the data that is included in the raw file. But my concern is this. It is my understanding that the initial conversion (before any personalized edits) of that raw file by Capture NX-D applies the camera WB setting to the rendered result. If, while still in NX-D, you make a WB adjustment, the software clearly has all the data still available to it to generate a different WB rendering.

My concern involves whether saving the result of an unadjusted conversion as a 16-bit tiff for further processing in PWP means that only the raw data necessary for that particular WB rendering is carried forward into the tiff and some data that might be useful for generating a different WB look is left behind. If that was the case, it would behoove one to do some white balance adjusting in NX-D before the tiff export. But Jonathan in his earlier post did not signal a strong warning about this.

Perhaps the answer is something like the following: If the WB is waaaaay off and requires a significant adjustment, you should definitely adjust it somewhat closer to a final result while still in the raw converter (but not necessarily all the way to "perfection"). But if WB is just a little bit off and needs only some minor tweaking perhaps you can safely leave all the color adjustments for PWP's Color Balance transform. After all, it is clear that you can do a fair bit of color balance adjusting with an 8-bit jpeg. And a jpeg file clearly has a specific WB "baked into" it and may have thrown away other data related to WB. So if the adjustment needed is not overly dramatic, perhaps using a 16-bit tiff that reflects the camera's WB is just fine.

This is the kind of advice that I was hoping Jonathan or Kiril would weigh in on. If what I conjectured above is correct. I would need to think about using the WB adjustment in NX-D for any images whose color was way off. So I went back and looked more closely at the NX-D WB controls. Although it doesn't have the flexibility of PWP's Color Balance transformation, I guess I ought to think about making an initial cut at a WB adjustment there if it was noticeably out of kilter.

Doug


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