Is Nikon Mode III really sRGB?

Started Apr 6, 2005 | Discussions thread
OP Bill Janes Senior Member • Posts: 1,848
Re: Why not multiple aRGBs?


Your post cleared up a lot of my misunderstanding of the profusion of sRGB settings on digital cameras. The renderings are different, but they all encode to the standard sRGB space.

Most experts (e.g. Bruce Fraser) recommend shooting in the raw mode and rendering into a wider color space such as Adobe RGB or ProPhotoRGB when the images are to be used for printing, since the sRGB space can't represent the gamut of a good digital camera.

Nikon cameras that I am familiar with have only one setting for aRGB. You can adjust contrast and saturation in Nikon Capture or Adobe Camera Raw, but selective enhachment of specific colors such as done in Mode IIIa of Nikon is not so easily done. Should cameras have selections for rendering into the aRBG space?

I see that you have a new book on color management for photographers. I had been intending to get Bruce Fraser's Real World Color Management book, but now I'll have to take a look at your book too.

Best regards,

Bill Janes

digidog wrote:

Funny, someone just emailed me off list about this so I'm going to
be lazy and cut and paste:

No camera initially produces sRGB. The RAW data is a Grayscale
file. When you ask the camera to provide a file in sRGB there are
two processes going on. The first is called rendering. The
Grayscale RAW to color image (known as demosaicing) happens. The
rendering it totally up to the manufacture to decide how they feel
they are producing the most pleasing color. If you shot an
identical scene with a Nikon and a Canon in sRGB, more than likely
the rendering would not be the same (maybe not even close). This is
much like the perceptual intent in ICC printer profiles. You can
measure the same target and build two different profiles and get
two different results. The manufacture has control over this
rendering. Note that when you bring a RAW file into a RAW
converter, this rendering process is now under your control. Just
as one RAW converter might have better (or worse) default
rendering, you the user can control this.

The next step is called encoding. The rendered color is encoded
into a color space. This is fixed and non ambiguous. Two identical
renderings will have identical encoding into a color space.

You'll note that many DSLRs have several settings for sRGB. This is
just a tweak to the rendering phase of the process. Think if it
like a "Velvia" setting versus an "Ekatchrome" setting whereby the
manufacturers are again not trying to produce a colorimetrically
accurate representation of the scene but rather the scene rendered
using various bias based on that image appearing on a display. IOW,
when you shoot an image of the scene, you're getting the
representation of that scene as it would appear on an sRGB display.

OK. I'm back. Note that when I say colorimetrically accurate
representation, I'm talking the measured color of the scene (which
includes stuff like the Illuminant, the dynamic range and so
forth). Colorimetrically correct color looks pretty ugly when
viewed on a display. It needs to be rendered (something called
output referred) to appear as we hope the scene to appear on this
output device.

What's interesting is few reviewers tell you how well the
manufacturers are doing with this on the fly rendering. And if they
compared the color based on RAW data, you'd have to factor in their
skill on rendering using some RAW converter (which one? Each plays
a role here).
Andrew Rodney
Author of Color Management for Photographers
The Digital Dog

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