Wednesday, February 11, 2009

Mysteries Of (Color) Space


We've covered it before and we'll cover it again because the ins and outs of color management begin with a firm grasp of how devices handle color space

source : Doug Sperling


Technical terms are frequently tossed around like a Frisbee in a park on Sunday. In digital imaging, three such terms are color space, color gamut and profiles. “Use this color space—you'll get better results.” “Is this color within the color gamut?” “What profile are you using?” All are valid questions, but what do they actually mean?

The industry's top hitters—Gretag-Macbeth, ColorVision, LaCie, X-Rite and others—have made analyzing color spaces, creating profiles and viewing a color gamut so user-friendly that what was untouchable to all except the ΓΌber-geek a few years ago now is accessible to all photographers who want complete control over their images. By making color management easier, manufacturers are helping to demystify these concepts. Color management is so increasingly commonplace, even among hobbyist consumers, that it has become a fundamental requirement for imaging professionals.



What Is A Color Space?

In general terms, a color space is all of the possible colors that an image can contain. Think of it like a box of crayons. If you use an eight-pack of Brand X crayons to sketch a bowl of fruit, your color space is that box of crayons. This color space will give you different options for creating your sketch than would a 16-pack of Brand Y crayons. A 64-pack would blow both of these away. You may not use all of the crayons for a given image, but it's nice to have the range. Think of color space as the digital equivalent of your box of crayons.

This is a simplistic analogy, but it helps to comprehend this basic concept before we dive into the more technical aspects of color spaces and color management. I base my understanding of color spaces and how they're used on a simple three-part workflow principle. You need to know: 1) from where your file came (source); 2) its present state (edit); and 3) to where it's going (destination).

There are two types of color space: working space and device space. Device space is the box of crayons to which you'll be limited when using a specific device, such as a camera, scanner or printer. We'll talk more about device space later. Most of the time, when people are talking about color space, they're referring to the working space.
Working Space Vs. Device Space

Working space is the color space you're using when you process a file with Photoshop or another color-managed imaging application. The most commonly used working spaces are Adobe RGB and sRGB. Other editing spaces include ProPhoto RGB, ColorMatch RGB and Apple RGB, to name a few. All of the working spaces are device-independent, meaning they're free from a device that has its own interpretation of what a particular color should be.

Device space is the space used by a particular device, such as a digital camera, scanner, monitor or printer. These devices have their own description of color based on what the manufacturer of the device thinks it should be, or on the technical limitations of the device, and rarely, if ever, do they match each other in terms of numerical values. For example, scan a swatch of Pantone Reflex Blue, which we know from Pantone is R=0, G=32, B=159. Scanner A may read the swatch as R=2, G=32 and B=159, and Scanner B may read it as R=0, G=33, B=158, and so forth. In other words, the two devices don't “see” the color in the same way, and neither sees it precisely according to Pantone's specifications. This phenomenon is known as device-dependent color.

So, if a scanner, digital camera, monitor or printer all collect, display and print color differently, how can one maintain consistent color from device to device, from capture to output? The answer is with a color-managed workflow incorporating and implementing ICC profiles.

Color Profiles And Gamut

Profiles are nothing more than files that describe (numerically) a characteristic of a certain device or color space and are used when converting from one space to another. When doing so, two profiles are needed—a source profile and a destination profile. Don't confuse destination profile with output profile. In certain instances, an output profile also may be a destination profile, but not always. For example, when converting from an input profile from a scanner to a working space such as Adobe RGB, the source profile is the scanner profile, and the destination profile is Adobe RGB (and, as we learned before, Adobe RGB is a working space, not a device space).

During conversion, color doesn't transform magically from one space to another. It goes through a profile connection space (PCS). This space encompasses all color and is the medium through which transformation takes place. This is a crucial step because color must be rendered properly so that any color within or outside the destination space's color gamut isn't compressed beyond desired results.

Each working space and device space has its own parameters of color, known as a color gamut.

This illustration represents all of the color in the visible light spectrum, or those colors to which the human eye is sensitive. Within the visible light spectrum resides the parameters, or gamut, of different color spaces. Note how much larger the gamut of ProPhoto RGB is compared to that of Adobe RGB and sRGB. Because Adobe RGB is within the boundaries of ProPhoto RGB, Adobe RGB is said to be within ProPhoto RGB's gamut. This isn't true of Adobe RGB's relationship with sRGB, as parts of the Adobe RGB space are outside the gamut of sRGB.

The implicit challenge lies in converting an image from a working space with a wide gamut to an output space with a smaller gamut.

If the editing space is Adobe RGB and our destination space is a printing press (which uses CMYK), then a tremendous amount of color and tonal compression will occur upon the color conversion. There are a lot of colors in the Adobe RGB gamut that can't be reproduced on the printing press. To help control that, specific rendering intents are used. We'll come back to rendering intents later in the context of output. First, let's take an overview of a color-managed workflow.

Typical Color Management

Implementation of color management begins at the capture of an image. Starting with the input profile from the scanner or digital camera, we go from the device space, through a PCS, into a working space such as Adobe RGB. Because we're displaying via a monitor with its own device space, the monitor must also be profiled to display the image properly.

To go from the working space to the correct output space, the output device also is profiled. The image will be taken from the working space and converted to the destination space for output (which could be offset press, inkjet printer or even sRGB for Internet use).

The real work begins when opening the image for processing. More often than not, the software used is Adobe Photoshop, and Photoshop needs to be set up properly—you might actually want to get some dialog messages to pop up when opening a file or when cutting and pasting a file from one image into another. The messages that need to be mentioned are “Missing Profile” and “Embedded Profile Mismatch.”

In order to receive these messages, you must enable them in the Color Settings preferences. Photoshop 7 and CS have Color Settings under the Photoshop pull-down menu on the Mac OSX platform. In CS2, it has been moved under Edit. Either way, the shortcut remains the same: Shift > Command K.

For the most part, I find U.S. Prepress Defaults to be a quick and standard setting because it uses Adobe RGB as the Working Space, sets all of the Color Management Policies to Preserve Embedded Profiles, and enables the Profile Mismatches and Missing Profiles warning messages. With my editing space set to Adobe RGB, however I acquire my files, Photoshop is on the lookout for files in which a different profile is embedded.

This lets me know that the image being opened isn't in my preferred working space. Under the “What would you like to do?” choices, I'd choose to “Use the embedded profile (instead of the working space).” It's typically best to keep and work with embedded profiles. Even though Adobe RGB has a larger gamut than sRGB, it will be of no benefit to bring an image into that larger working space. I won't be gaining color, as you can't make up color with a conversion. If the color isn't there to begin with, then you won't have it. A general rule of thumb is to do as few transformations as possible; only do them if necessary. With every transformation, you're affecting the color to some degree, either massively or minutely. You may find that some files don't have an embedded profile.

Because the source of the image is unknown in this situation, there's nothing wrong with experimenting with different profiles. You might consider simply using sRGB, or your usually preferred working space. You're now ready for editing.

Preparing For Output

When the image is ready for output, the workflow continues by taking the image from its working space and preparing it for output—in this case, a print from an Epson printer. Select File > Print With Preview in Photoshop. Here's where the output space is defined by using a printer profile.

After the proper printer profile is entered, click on Print. Make sure that No Color Adjustment is checked. Failure to do so will put a double whammy on your color. Even if Color Controls is selected and everything is zeroed out, you're still affecting the color. Set the proper quality settings, paper stock and resolution in Print Settings as well (which can be found in the same pull-down menu as Color Management).

The last important consideration is dealing with rendering intents, as there are decisions to be made in the Color Settings preference and the Print With Preview dialog. Rendering intents basically allow for choices to be made on the types of transition from one color space to another. There are four basic options of rendering intents: perceptual, relative colorimetric, absolute colorimetric and saturation.

Perceptual Rendering

Notice there are four points of color (represented by black dots). Two are “out of gamut” to the smaller gamut, and two reside in both gamuts. When converting from the larger gamut to the smaller one, tonal compression must occur. With perceptual rendering, the software attempts to maintain proportion in the overall color relationships. Notice in the illustration that all color points have moved, even those that were well within the smaller gamut, in order to maintain those relationships.

Relative Colorimetric

We see the effects of relative colorimetric rendering. The out-of-gamut colors get clipped (Point A) while the colors contained in the smaller gamut remain unchanged (Point B). This ensures that what we see as a white point from the source is remapped as a white point on our output. Typical uses for this rendering are printing, CMYK conversions and, sometimes, press simulation.

Absolute Colorimetric

Absolute colorimetric is used mainly for proof simulation when wanting an RGB device to match that of a CMYK device. With absolute colorimetric, the white points will change to account for the base-paper white of the simulated stock. In other words, if the paper on which the RGB device is printing is fairly bright, there's no way the print will match that of a printing press' yellowish, dingy paper. I realize that “yellowish” and “dingy” are harsh descriptors, but, let's face it, it's terrible stock in comparison. In any event, the RGB device will lay down some extra ink to simulate the proofing stock. Hence, your highlights may look yellowish and dingy.

Saturation

As the name implies, this intent will saturate the colors for visual appeal. This is used for graphic slides and overhead projectors for presentations.

Between the perceptual and relative colorimetric rendering intents, relative colorimetric seems to be doing the job, for the most part. Perceptual rendering is selected most often when there are a lot of colors that are out of gamut and need to be brought in as much as possible.

Your homework assignment is to acquire an image, employ the color-managed workflow and bring in one image two different ways—one using sRGB and the other using Adobe RGB. Output the images to your printer and convert using both relative colorimetric and perceptual renderings. Try the same method on a subject of very muted colors and another subject of very saturated colors. See any difference?

What, Me, Worry?

Being a professional photographer today requires that you have at least a working knowledge of color space issues and, therefore, an understanding of how to deliver the best image to your client. While we endorse the notion of complete color management from beginning to end in your workflow, the fact remains that once the image leaves your workspace, that's the end of your control, and the image will be at the mercy of the color management of your client. The best you can do is hope that they have been as diligent as you have.

Monday, December 15, 2008

GO GREENER


GO GREEN Action is starting from our self.

We might hear a lot about Go GREEN campaign lately. What is it? Simply I can say that’s another campaign for better and greener environment. If you wanna know further, just go googling, find them out on the internet (i'm not good in explaining) he he he

Well I just wanna share what I’ve done to go Greener since years ago.

REDUCE, REUSE, RECYCLE.


Some efforts I did:

1. Took shower once a day (sometimes, if possible, I didn’t shower at all for a day, especially when Ina, my wife, was not around) and wear my blue jean for a week. Means less consumptions of water, chemical (soap, detergent, n shampoo) and electricity power as well.

2. Made almost of all my furniture at my home from used materials. (Eg. My drawer, closet, book shelf, cup board, kitchen set, bed, table and all wooden stuff etc) Used material I got from “Maduresse” who sold ex - engine packaging wooden box, usually they got them from industrial complex. Their Lapak (kiosk) could be found along the Lenteng Agung Street or some Jakarta sub-urb areas. What I did was just sketched the design, call the carpenter, and supervised by my self. Oh ya, for the final touch I usually cover them up with a vinyl sheet called “Tacon” so they looked like a brend new "minimalist" furniture. You can find those tacon things @ "toko-material" on Panglim Polim street BLOK A jaksel. (tips : go to Index Store grab some leaflet or Ikea catalogue, or go to internet find a model, print them out, then imitate them…). Of course they would cost less with better material quality.

3. Reduced the consumption of paper means save our forest, if necessary , never print all printable document (including photos). Use water to clean up your “private area” after “toilet business” instead of using toilet paper.

4. Turned OFF all of electric consuming gadget when not in use, such as lap top, TV, radio, Air conditioner, lights etc. Oh ya, unplugged the mobile charger when not in use.

5. Briought along my own bag, when I went to groceries store such as Carrefour, and if forgot, I asked the Cashier for carton boxes instead of plastic bags.

6. Used public transportation, if not picked a scooter instead of a car. Less Gas consumption means less pollution and save some more money…hehhehe..

7. Worked @ home if it is possible.

8. Made a fun used material project.( I've been doing some)

9. Planted more trees around the house.
(to be continued)

MY UN-PRODUCTIVE DAY IS MY BEST QUALITY TIME

It was Saturday... yeehaaa another precious weekend, means free-day as free as "no need to shower day", yep all of us did not shower yet by the time this photo was taken.
We were just wandering around the neighborhood on my "new" used scooter bike, given by my brother in Law "Mene" who had left for the states for uncertain number of years....
Kind of weird to be on the motorbike again since the university, it was cool tho. My baby Mahija (2,5 yo) loved it so much, wow..
Besides it also means more "bubur ayam" (chicken porridge) to explore.
It is true, the wise old saying : "your un-productive days are your best quality times indeed" (actually I made it up hehhehe).
Let spend more quality times with people we love

Saturday, December 6, 2008

MACIOUS greets you APAKABAR?



My name is Yus prinandy and I make a living by doing digital imaging, explains why they call me a digital artist or well known as a creative-retoucher besides I do Photowork as well.(sometimes i was invited to be a keynote speaker on some photography seminars and did some tutorials on Photoshop)
Then why It's named MACIOUS (read = mas iYus). I got that name from my fellow photographers in 2005 from a class of a Photography School I attended and now people starts to call me that way. Considered as a real Javanese person with a "jawir" accent, they put Mas before my name Yus, means big brother in Javanese language. or a form of respect for the senior people (like me ha?) or was it because of my size and shape? Only God and they know why..hehe..
In Old Greek language, taken from word Con'tu macious, Macious means rebel or rascal since it becomes my middle name ha..ha.., which i love to be identified as a rebel for ideas and creativity. So why should make up a new name instead of modify the existing? coz it is what i am..
I love to modify everything into a different form and usage. (though sometimes i do manipulate them..he...he..) that's why people define you through "you are what you do" term.
finally....
SELAMAT DATANG to my blog