Color Management in Nikon Capture NX
I wanted to expand upon something I mentioned last week regarding the new Nikon Capture NX. Yes, the rumors are true: Nikon has finally given us a real color management implementation. Here's how it works.
First, for those not familiar with color management, the idea is to be able to describe how every device (printer, monitor, and so on) in your workflow reacts to color and then use the resulting profiles to translate between them to keep things looking consistent. You can find a lot more background on how all this works from some of the other weekly PhotoTips articles I've posted here on the site. Previous versions of Nikon Capture offered very primitive color management support. While not perfect, the situation has much improved with the release of Nikon Capture NX.
Let's start by taking a look at the Capture NX color management preferences located on the menu under Edit >> Preferences >> Color Management. The dropdown list at the top of this tab allows you to select the default rendering intent to be used throughout Capture NX. In a sense, it doesn't matter what you set this to since you can override this default as needed in the other dialog boxes we will look at this week. For most purposes though, you will ultimately want to select either Relative Colorimetric or Perceptual intent, so picking one or the other here can make things marginally easier later.
The checkbox underneath the RGB profile to "Use black point compensation" similarly sets the default for this option throughout Capture NX. Turning this on tells NX to map the blackest black in your image to the blackest black in your printer profile and other color management conversion situations. With few exceptions, you should turn black point compensation on and leave it that way.
The function of the Default RGB color space dropdown list depends on whether or not you also check the box underneath it to "use this instead of embedded profile." With the box unchecked, Capture NX will use the color space you select here when you open an image that does not contain an embedded profile tag. All images shot on any current Nikon camera will have profiles so this option generally gets ignored. If you open jpeg or tiff images from other sources though that do not contain a profile, Capture NX would have no way to correctly interpret what colors are meant by the RGB pixel data without you cluing it in as to what the profile should be. When installing Capture NX you are asked what default RGB space you wish to use, but there is no need to obsess over the choice at that time since you can change it here later.
If instead, you check the "use this instead" checkbox, then Capture NX will use your selected profile for all images, even though tagged with a different profile. What this means though depends on whether the image is a raw (NEF) file or some other format. Since raw files aren't yet actually in any color space but are merely tagged with an indication of your preferred profile, forcing Capture NX to use a different one merely changes how the raw data gets converted but not what the image ends up looking like. It is the equivalent of changing your mind after the fact on which profile to shoot in. If you shot raw images in sRGB but wish you had chosen Adobe RGB, you can coerce Capture into converting into Adobe RGB in this way with no loss of quality. If you shot in Adobe RGB but wish Nikon had given you the choice of using ProPhoto RGB, you can do that too, giving you access to an even wider gamut.
But if the image you open is not a raw file, then it already has a color space whether it is tagged with one or not. That is to say, you may have no way to know definitively what the profile should be, but the red, green and blue data will only look "correct" if you interpret it as was intended. Choosing a different profile will alter how the image looks, many times, though not always, for the worse. If you don't like the results when opening an image with this option set, you must close the image, change your preferences, and try opening it again.
The Color management preferences also let you select your default Printer Profile, saving you a bit of time when you print. If you check the box underneath to "Use this profile when printing," then the actual print dialog will come up with color management already enabled. It will, too, if you enable soft proofing as described later in this article.
The CMYK separation profile can generally be ignored. If you do use Capture NX to save tiff images in CMYK though, you can select your desired profile here.
Once you have an image open in Capture NX, you can use Adjust >> Color Profile to change its color space. When you open the dialog, you will find two options, labeled "Apply" and "Convert." Apply should really be called Assign since this is the more common term for what this option does. Indeed, the Capture NX Users Guide acknowledges this by its description of Apply: "Choose Apply Profile to assign a profile to the current image. This option is most often used when you would like to assign an input profile, such as a profile you created for your camera, to the image." So why not simply call it Assign? Got me. At any rate, you can use it to re-interpret the RGB data in an image using a different profile. The data in the file will not change, but its appearance will.
Converting to a profile is luckily called by its familiar name and functions the same as the equivalent option in Photoshop. The data in the file will be changed so that the image remains looking the same in the new color space. When you save images for the web or email, you should convert them to sRGB first. You can find more on the difference between converting and assigning here.
Converting or Applying (assigning) profiles in Nikon Capture NX
Enabling soft proofing in Nikon Capture NX
Nikon Capture NX now supports Soft Proofing to enable you to approximate how an image will look when printed before investing the time, paper and ink in actually printing it. Inexplicably though, you will not find it on the program's menus. Instead, the option is hidden in plain sight on the bottom margin of each image window. Clicking on the dropdown option opens a new window where you can select your printer profile, desired rendering intent and whether you want to use black point compensation. Whatever you have selected in Preferences for these options will come up as the defaults, but you can freely change things here if you use different paper types or want to change other settings. Some images look better with Relative Colorimetric intent while others with Perceptual. When turned on, Soft Proofing lets you see the effect of your printer gamut by converting the image data on the fly. It's called soft proofing since the RGB numbers in your file don't actually change; it just looks like they do. You can then add any needed Edit Steps to restore contrast or saturation before printing. Overall, soft proofing works the same as it does in Photoshop so you should feel right at home if you are used to how Adobe does this.
When you actually go to print, you can choose your color management options at File >> Print >> Color Management. If you have turned on soft proofing or have checked the box in Preferences to use the printer profile selected there when printing, your choices will automatically come up as desired in the Print dialog. If not, you can pick your desired profile, rendering intent and such here directly. In any case, if you use the color management options when printing from Capture NX, be sure to turn them off in your printer driver to avoid double profiling.
Printing from Nikon Capture NX
All in all, Nikon and Nik Software did a fairly good job of adding support for color management to Capture, but things are far from perfect. Most notably, there is a lack of acknowledgement of how editing a raw (NEF) image differs from editing other image formats. The data in a raw image has only a single channel of linear data and is thus not yet in any RGB color space. To be viewable at all, the raw data has to be de-mosaiced, gamma corrected, and interpolated to form separate red, green and blue channels in some color space. When doing so, you should be able to make use of the full gamut of any RGB profile (within the limits of what the camera recorded of course). But Capture NX gives you a very poor way of changing it. You must edit your Preferences before opening the image to select the desired profile and check the box underneath to force NX to use it. There is no way to "try out" various profiles directly when opening an image. You can of course later use Convert Profile to select a different profile, but at this point the raw data will already have been limited to the gamut of the profile used to open the image.
And confusingly, this Preferences checkbox works completely differently for non-raw images, effectively applying (assigning) it rather than converting to it. And if you find you had it set wrong when opening an image, you must close the image, change the setting and then re-open the image to correct things. This is cumbersome at best.
Much of the blame for this confusion seems to stem from the apparent way that Capture NX came into being. At the heart of NX is essentially the same program that Nikon shipped as Capture 4.4. This was then wrapped over by the new code including the U-Point technology that Nik Software brought to the project. While new soft proofing and printing color management choices where added to NX, much of the color management options in the Preferences dialog remain unchanged from Capture 4.4. Nikon didn't have it right then any more then they do now. It would have made a great deal more sense had they added an option under Base Adjustments to directly change the color space, much as they long have had for what Nikon calls "color mode." It seems more than a little odd to open a raw image into one color space, then use an Edit Step to later convert profiles using Adjust Profile rather than simply allowing the user to change the profile used to open it in the first place. I applaud Nikon for finally improving profile support in Capture, but the one color management control most useful for raw files is still poorly implemented. By contrast, Adobe Camera Raw, DxO Optics Pro and others allow you direct access to the profile used by the raw conversion engine.
The other notable glitch at least on the Windows platform has to do with how profiles get listed (or not listed) in the various dropdown lists. Photoshop scans and lists all profiles found under C:\WINDOWS\system32\spool\drivers\color or any subdirectories underneath. Capture NX instead relies on reading the Windows Registry to enumerate available profiles, and profiles are only listed in the Registry if they have been officially "installed" by Windows. If you right-mouse-click on any ICC or ICM profile file and select "install profile," Windows will copy it to the color folder and add it to the registry. The new XP Color Control Panel applet has the same requirement, so this isn't really Nikon's fault but is more one of Microsoft's oddities. Adobe has no trouble finding profiles simply by looking where they belong, but it seems that Microsoft and Nikon insist they be listed in the Registry as well. This wouldn't be a major drawback though if it didn't insist on copying profile files into the root of the color folder, even when they are already in a subdirectory. When officially installing a profile from a subdirectory under C:\WINDOWS\system32\spool\drivers\color, Windows will create a duplicate copy in the root of spool\drivers\color. If like me, you want to organize your profiles into subfolders to help keep track of them, you are forced into manually deleting the duplicates and editing the Registry entries to point to the ones in your subfolders. Even after installing them by the way, they don't get listed in any meaningful order in the Capture NX dropdown lists. At least in my testing, they seem to pretty much be in random order, making it hard to find what you are looking for.
While there is indeed still notable room for improvement in an eventual Capture NX version 2, Nikon has indeed made huge strides in color management support in this initial release. In my opinion, anything that gets better color management tools into the hands of photographers is a good thing. Kudos to Nikon and Nik for stepping up and trying to address this.
Update 7/16/2006 - The problem of profiles not sorting themselves alphabetically seems to be a Windows only issue. I now have the trial of Nikon Capture NX installed on MacOS as well and they sort correctly there.
Update 9/29/2006 - Version 1.01 of Capture NX seems to have fixed at least one of these problems. Checking the box in Color Management Preferences to "use this instead of embedded profile" no longer uses the selected profile instead of the embedded profile. It now correctly converts from the embedded profile. Inexplicably, the terminology in Prefrences remains as it was.
Update 4/27/2007 - A reader pointed out that I neglected to mention how the Browser built into Capture NX handles color management issues, an oversight on my part. It's not really among NX's best features though so I'm going to forgive myself for leaving it out. But for completeness sake, the browser gets its speed by using the jpeg embedded inside each NEF file rather than the actual raw data. It is not truly color management aware. Use it to find the images you want to work on, but don't rely on it for critical judgments of color.